Alfred M. Kracht, Visitor 阿尔弗雷德·M·克拉赫特, 访客There is no doubt that bulbous bows improve most of the properties of ships, but the correct design 毫无疑问,球形船首改善了船舶的大多数性能,但正确的设计and power prediction for ships with bulbous bows are still difficult due to the lack of design data. In 由于缺乏设计数据,带有球鼻的船舶的功率预测仍然困难。the paper, a quantitative design method is presented together with the necessary data providing rela- 本文提出了一种定量设计方法,并提供了必要的数据支持tionships between performance and main parameters of ships and bulbs. The data, in the form of 船舶和灯泡的性能与主要参数之间的关系。数据以以下形式呈现:design charts, are derived from a statistical analysis of routine test results of the Hamburg and the 设计图表源自对汉堡和常规测试结果的统计分析Berlin Model Basins, HSVA and VWS, respectively, supplemented by results of additional tests to 柏林模型水池、HSVA 和 VWS,分别由额外测试的结果补充fill the gaps. Three main hull parameters are taken into account: block coefficient, length/beam 填补空白。考虑三个主要船体参数:块系数、长度/宽度。ratio, and beam/draft ratio, while six bulb quantities are selected and reduced to bulb parameters, 比率和梁/吃水比,同时选择六个灯泡数量并减少到灯泡参数,of which the volume, the section area at the fore perpendicular, and the protruding length of the bulb 其体积、前垂直截面积和灯泡的突出长度are the most important. For power evaluation, the total power is subdivided into a frictional and a 是最重要的。对于功率评估,总功率被细分为摩擦功率和一个residual part. Depending on bulb parameters and Froude number for each block coefficient of the 残余部分。根据每个块系数的灯泡参数和弗劳德数。main hull, six graphs of residual power reduction have been prepared. Because of the wide range 主船体,已准备六个残余功率减少的图表。由于范围广泛of block coefficients, there are so many design charts that only one example is presented herein. 关于块系数,有很多设计图表,这里仅提供一个示例。
Introduction 介绍
Nearly 90 years ago, R. E. Froude interpreted the lower resistance of a torpedo boat, after fitting of a torpedo tube, as the wave reduction effect of the thickening of the bow due to the torpedo tube. D. W. Taylor was the first who recognized the bulbous bow as an elementary device to reduce the wavemaking resistance. In 1907 he fitted the battleship Delaware with a bulbous bow to increase the speed at constant power. In spite of great activities in the experimental field to explore its potential, 70 years had to pass before the bulb finally asserted itself as an elementary device in practical shipbuilding. A suitably rated and shaped bulb affects nearly all of the properties of a ship. Especially for fast ships, the use of a bulb allows a departure from hitherto accepted design principles for the benefit of a better underwater form. The higher building costs are the only disadvantage. 近 90 年前,R. E. Froude 解释了鱼雷艇在安装鱼雷发射管后较低的阻力,认为这是由于鱼雷发射管导致船头增厚的波浪减小效应。D. W. Taylor 是第一个认识到球形船头作为减少造波阻力的基本装置的人。1907 年,他为战列舰德拉瓦州安装了球形船头,以在恒定功率下提高速度。尽管在实验领域进行了大量活动以探索其潜力,但在实际造船中,球形船头的应用直到 70 年后才得以确立。合适的形状和尺寸的球形船头几乎影响船舶的所有特性。特别是对于快速船舶,使用球形船头允许偏离以往接受的设计原则,以获得更好的水下形状。更高的建造成本是唯一的缺点。
The protruding bulb form affects hydrodynamically a variation of the velocity field in the vicinity of the bow, that is, in the region of the rising ship waves. Primarily the bulb attenuates the bow wave system, which usually is accompanied by a reduction of wave resistance. By smoothing the flow around the forebody, there is good reason to believe that the bulb tends to reduce the viscous resistance too. Therefore, the beneficial action of a protruding bulb depends on the size, the position, and the form of the bulb body. See Fig. 1. 突出的球泡形状在船头附近,即上升船波的区域,影响了速度场的变化。主要是球泡减弱了船头波系统,通常伴随着波阻力的减少。通过平滑前体周围的流动,有充分理由相信球泡也倾向于减少粘性阻力。因此,突出的球泡的有益作用取决于球泡体的大小、位置和形状。见图 1。
The linearized theory of wave resistance has provided the main contribution to the understanding of the bulb action (Wigley [3], Weinblum [4|, Inui [5,6]). But it is of no great use for the project engineer. In the preliminary stage of his project, he needs fundamental information on which to base concrete decisions. Later, in the realization stage, the quantitative as well as qualitative guidelines are important, because the hydrodynamic phenomena are not describable by few geometric form parameters alone. For this reason, in this paper, the mode 波阻力的线性化理论为理解船首球的作用提供了主要贡献(Wigley [3],Weinblum [4],Inui [5,6])。但对项目工程师来说,这并没有太大用处。在项目的初步阶段,他需要基本信息以便做出具体决策。后来,在实现阶段,定量和定性指导都很重要,因为水动力现象不能仅通过少量几何形状参数来描述。因此,在本文中,模式
Fig. 1 Bow wave pattern of a model without (upper picture) and with bulbous bow (lower picture) 图 1 无(上图)和有球鼻(下图)模型的波浪模式
of action of a bulb and the influence of bulb parameters on resistance or power reduction, respectively, are described in a qualitative manner; guidelines for bulb design are also introduced. The design charts presented here are the result of a research project; that is, of an analysis of routine test results, of the Hamburg and the Berlin Model Basins supplemented by results of additional tests to fill the gaps. The charts are new and therefore still in need of improvement and completion. 灯泡的作用及其参数对电阻或功率降低的影响以定性方式描述;同时也介绍了灯泡设计的指导原则。这里呈现的设计图表是一个研究项目的结果;即对汉堡和柏林模型水池的常规测试结果的分析,并通过额外测试的结果来填补空白。这些图表是新的,因此仍需改进和完善。
a, -Type a, -类型
b, 0 - Type b, 0 - 类型
Fig. 2 Bulb types 图 2 灯泡类型
c, - Type c, - 类型
Bulb forms and parameters 灯泡形状和参数
For an adequate presentation of the hydrodynamic properties of bulbs, it is necessary to systematize the different existing bulb forms by means of geometric parameters. Obviously a definitive description of a bulb shape, just as for a ship form, with a finite number of geometric parameters, is impossible. But a rough classification is possible using only few parameters. 为了充分展示灯泡的水动力学特性,有必要通过几何参数对不同的灯泡形状进行系统化。显然,像船体形状一样,用有限数量的几何参数对灯泡形状进行明确描述是不可能的。但可以仅使用少量参数进行粗略分类。
With the shape of the cross section of the bulbous bow at the forward perpendicular as the main criterion, one can differentiate three main bulb types (Fig. 2) |8|: 以前垂线 处的球形船头横截面 的形状为主要标准,可以区分三种主要的船头类型(图 2)|8|:
(a) -Type: Fig. 2(a) shows the drop-shaped sectional area of the delta-type with the center of area in the lower-half part. This shape indicates a concentration of the bulb volume near the base. The Taylor bulb and the pear-shaped bulbs belong to this type. (a) -类型:图 2(a)显示了三角洲型的滴状截面积 ,其面积中心位于下半部分。这个形状表明灯泡体积在基部附近集中。泰勒灯泡和梨形灯泡属于这一类型。
(b) O-Type: This type (Fig. 2b), with an oval sectional area and a center of area in the middle, has a central volumetric concentration. All the circular, elliptical, and lens-shaped bulbs as well as the cylindrical bulbs belong to this type. (b) O 型:这种类型(图 2b)具有椭圆形截面 ,其面积中心位于中间,具有中心体积浓度。所有圆形、椭圆形和透镜形的灯泡以及圆柱形灯泡都属于这一类型。
(c) -Type: The nabla-type also has a drop-shaped sectional area (Fig. 2c), but its center of area is situated in the upper-half part, indicating a volume concentration near the free surface. Because of its favorable seakeeping properties, this type is the most common bulb. (c) -类型:nabla 型也具有一个滴状的截面积 (图 2c),但其面积中心位于上半部分,表明在自由表面附近存在体积集中。由于其良好的航行性能,这种类型是最常见的球形。
With respect to the lateral contour of the bulbous bow, two typical classes are distinguishable: 关于球形船头的侧面轮廓,可以区分出两种典型类型:
(a) The stem outline remains unchanged as with the Taylor bulb. These bulbous bows do not have favorable properties and are no longer built today. (a)干茎轮廓与泰勒灯泡保持不变。这些球形船头没有良好的特性,今天不再建造。
(b) The stem outline is changed by the protruding bulb as with all modern bulbous bows. (b)茎轮廓因突出的灯泡而改变,就像所有现代球形船首一样。
In addition to these classification criteria, quantitative bulb parameters are necessary for delineation of the bulb form. The author is of the opinion that six parameters are sufficient for all practical purposes. Figure 3 shows the three linear and three nonlinear geometric bulb quantities that are reduced to the bulb parameters, that is, normalized by the main dimensions of the ship, as described in the following. 除了这些分类标准,定量的灯泡参数对于灯泡形状的划分是必要的。作者认为六个参数对于所有实际目的来说是足够的。图 3 展示了三种线性和三种非线性几何灯泡量,这些量被简化为灯泡参数,即通过船舶的主要尺寸进行归一化,如下所述。
The three linear bulb parameters are 三个线性灯泡参数是
The breadth parameter, that is, the maximum breadth of bulb area at the divided by the beam of the ship 宽度参数,即在 处灯泡区域 的最大宽度 除以船只的光束
The length parameter, that is, the protruding length normalized by the of the ship 长度参数,即船舶的 标准化的突出长度
The depth parameter, that is, the height of the foremost point of the bulb over the base divided by the draft at the 深度参数,即灯泡前端点的高度 与 处的吃水 之比
The variation of the linear bulb parameters is easily possible during the project phase. The breadth is not necessarily the maximum breadth of the bulb body that, for hydrodynamic reasons, can also be located before the FP. The depth pa- area of ram bow in longitudinal plane, 在项目阶段,线性灯泡参数的变化是很容易实现的。宽度 不一定是灯泡主体的最大宽度,出于流体动力学的原因,它也可以位于 FP 之前。纵向平面中的深度 pa- 区域的撞击船首, cross-sectional area at forward perpendicular (FP), 在前垂直面 (FP) 的横截面积, midship section area, 中部截面面积, maximum breadth of bulb area 灯泡区域的最大宽度 beam, midship, m 横梁,中船,米 block, midship-section, prismatic, and waterline coefficients, respectively 块,中部截面,棱柱形和水线系数,分别 prismatic coefficient, entrance 棱镜系数,入口 frictional or residual resistance coefficient, respectively 摩擦或残余阻力系数,分别 residual power displacement coefficient 残余功率位移系数 residual power reduction coefficient 残余功率降低系数 lateral parameter 侧向参数 cross-section parameter 截面参数 breadth parameter 宽度参数 length parameter 长度参数 volumetric parameter 体积参数 depth parameter 深度参数 diameter of propeller, or wake field, respectively. m 螺旋桨直径或尾流场,单位:米。 Froude number 弗劳德数 total height of 总高度为 length of entrance, or between perpendiculars, respectively, 入口的长度,或在垂直线之间,分别是 protruding length of bulb, m 突出灯泡的长度,米 delivered, frictional, or residual power, respectively, PS effective frictional or effective residual power, respectively, PS 交付的摩擦功率或剩余功率,分别为 PS 有效摩擦功率或有效剩余功率,分别为 PS residual power reduction factor 残余功率降低系数 frictional, total, or viscous resistance, respectively, kp 摩擦、总和或粘性阻力,分别为 kp viscous residual, wave-breaking, or wavemaking resistance, respectively, kp 粘性残余、破浪或造浪阻力,分别为 kp bulb effect on wave-breaking or wavemaking resistance, respectively, kp 灯泡对破浪或造浪阻力的影响,分别为 kp secondary bulb effect, bulb effect on viscous resistance, kp 次级灯泡效应,灯泡效应对粘性阻力的影响,kp Reynolds number 雷诺数 ship surface or total bulb surface, respectively, 船体表面或总球泡表面,分别是 draft at or midship, respectively, m 草稿在 或中船,分别为 m ship speed, knots 船速,节 total bulb volume, 总灯泡体积, volume of protruding bulb part, 突出球部的体积, displacement volume, 排量, height of the foremost bulb point over baseline, m 前端灯泡点相对于基线的高度,米 thrust deduction or wake fraction, respectively 推力扣除或尾流分数,分别 propulsive efficiency 推进效率 viscosity of water, 水的粘度, density of water, 水的密度, acceleration due to gravity, 重力加速度,
Fig. 3 Linear and nonlinear bulb quantities 图 3 线性和非线性灯泡数量
rameter is a valuation factor of the beach slope of the bulb top (thick line in Fig. 3). 参数是灯泡顶部海滩坡度的估值因素(图 3 中的粗线)。
The three nonlinear bulb parameters are 三个非线性灯泡参数是
The cross-section parameter, that is, the cross-sectional area of the bulbous bow at the divided by the midship-section area of the ship 横截面参数,即船首的横截面积 与船中部横截面积 的比值
The lateral parameter, that is, the area of ram bow in the longitudinal plane normalized by 侧向参数,即在纵向平面中由 标准化的冲角 的面积
The volumetric parameter, that is, the volume of the protruding part of the bulb divided by the volume of displacement of the ship 体积参数,即灯泡突出部分的体积 与船舶的排水量 之比
The volume is the nominal bulb volume. The total or effective bulb volume is the sum of and the fairing volume , which results from the fairing of the bulb into the ship hull. 体积 是名义灯泡体积。总或有效灯泡体积 是 和整流罩体积 的总和,整流罩体积是由灯泡整流到船体中产生的。
Finally, a distinction is possible between an additive and an implicit bulb. An additive bulb increases the displacement volume of the ship by the effective bulb volume . The sectional area curve of the original hull remains unchanged. On the other hand, the effective volume of an implicit bulb is part of the displacement volume of the main hull that is shifted from unfavorable regions and concentrated in the vicinity of the forward perpendicular. By this process, the sectional area curve of the original ship is changed. 最后,可以区分加法型船首和隐式船首。加法型船首通过有效船首体积 增加船舶的排水体积 。原始船体的断面面积曲线保持不变。另一方面,隐式船首的有效体积 是主船体的排水体积 的一部分,这部分体积从不利区域转移并集中在前垂线附近。通过这个过程,原始船舶的断面面积曲线发生了变化。
Influence of a bulbous bow on the properties of a ship 船舶球形船首对性能的影响
Before discussing the influence of the bulbous bow on the ship's resistance and required power, respectively, we should mention other important hydrodynamic qualities which play a role in the decision whether a bulb should be used or not. The change of resistance influences the thrust loading of the propeller and, consequently, other propulsive characteristics of the ship; for example, the quasi-propulsive coefficient, the wake, and the thrust deduction fraction [9-11|. Figure 4 shows this indirect influence of a bulbous bow on thrust deduction and wake fraction. Both are increased by an additive as well as by an implicit bulb, if the bulb ship has a lower total resistance than the bulbless form. But there is also a direct influence of the bulbous bow on the wake distribution in the propeller plane In Fig. 5 the radial distributions of axial wake components of ships with and without a bulb are compared. Within the propeller disk area the axial wakes of all bulb ships are higher 在讨论球鼻船首对船舶阻力和所需功率的影响之前,我们应该提到其他在决定是否使用球鼻的重要水动力特性。阻力的变化影响螺旋桨的推力负荷,从而影响船舶的其他推进特性;例如,准推进系数、尾流和推力扣除系数。图 4 显示了球鼻对推力扣除和尾流系数的间接影响。如果球鼻船的总阻力低于无球鼻形式,则两者都会因附加和隐含的球鼻而增加。但球鼻对螺旋桨平面尾流分布也有直接影响。图 5 比较了有球鼻和无球鼻船舶的轴向尾流分量的径向分布。在螺旋桨盘区域内,所有球鼻船的轴向尾流都更高。
Fig. 4 Influence of a bulbous bow on thrust deduction and wake fraction (- . . - with, - - without bulb) 图 4 球形船首对推力扣除和尾流分数的影响(- . . - 有球形船首,- - 无球形船首)
Fig. 5 Influence of a bulbous bow on the radial distribution of circumferencial average nominal axial wake component (- . . . . . with, -— without bulb) 图 5 球形船首对周向平均名义轴向尾流分量的径向分布的影响(- . . . . . 有球形船首,-— 无球形船首)
than the wakes of the bulbless ones. The reason for this is the change of flow around forebody and bilge, which is observable in the model case up to the propeller disk \12,13]. But in the correlation of model test and full-scale results, scale effects play a very important role [10] and it is not certain if this bulb effect is also found at the ship. 比无泡沫船体的尾流要好。这是因为在船首和舱底周围的流动变化,这在模型案例中可以观察到,直到螺旋桨盘\12,13]。但是在模型试验与全尺度结果的相关性中,尺度效应起着非常重要的作用[10],并且尚不确定这种泡沫效应是否也存在于船上。
Although unfavorable effects are possible, bulbous bows in general do not influence the course stability or the maneuverability [14]. No significant changes of the overshoot angle or the period in zigzag tests could be established. The bulb is an ideal place for the arrangement of bow thrusters and acoustic sounding gears. 尽管可能存在不利影响,但一般来说,球形船首不会影响航向稳定性或机动性[14]。在锯齿形测试中,未能确定超调角或周期的显著变化。球形船首是布置船首推进器和声学探测设备的理想位置。
The seakeeping qualities of a ship are a special problem, and a very broad field, which will be discussed here only briefly. 船舶的抗波性能是一个特殊的问题,也是一个非常广泛的领域,这里将仅简要讨论。
Fig. 6 图 6
Damping coefficient of partially immersed bulbous cylinders as function of wave number 部分浸没的球形圆柱体的阻尼系数 作为波数 的函数
Except for the relative foreship motion against the water surface, the bulbous bow has no unfavorable influence on either the remaining motions or on the maximum bending moment in the midship section [15, 16]. In spite of the higher relative motion of a bulb ship, the danger of slamming of a well-shaped bulb is no higher than with the bulbless ship [17). In detail, the bulb mitigates the pitching motion of the ship by its higher damping. It should be mentioned here that the damping coefficient of bulb cylinders in a two-dimensional case vanishes for a certain wave number |18| as shown in Fig. 6. Since nonbulbous cylinders do not show this quality, the damping effect of a bulbous bow, for example, of O-type, can vanish for definite wave numbers, and the bulb ship moves like a bulbless one. 除了相对于水面相对前进运动外,球形船首对其余运动或中船段的最大弯矩没有不利影响[15, 16]。尽管球形船的相对运动较大,但形状良好的球形船的撞击危险并不比无球形船高[17]。具体来说,球形船首通过其更高的阻尼减轻了船的俯仰运动。这里需要提到的是,在二维情况下,球形圆柱的阻尼系数在某个波数下消失|18|,如图 6 所示。由于无球形圆柱不具备这种特性,因此例如 O 型的球形船首的阻尼效应可能在特定波数下消失,球形船的运动就像无球形船一样。
In regular waves, model tests show that the critical Froude number from which the bulb ship begins to be superior increases with increasing ratio . As a function of at constant Froude number, the resistance of a bulb ship increases more rapidly than that of the bulbless form. Therefore, most of the smooth-water advantages of bulb ships vanish above about . In irregular waves, nearly all bulbous ships have disadvantages above Beaufort 8 . Since in the North Atlantic the probability of the occurrence of wind intensity more than Beaufort 8 is only about 10 percent, and up to the bulbous ship is the best ship [20] regardless of seakeeping aspects, the bulb design consequently may be carried out in view of the smooth-water performances only. 在规则波浪中,模型试验表明,灯泡船开始优越的临界弗劳德数 随着比率 的增加而增加。在恒定弗劳德数下,灯泡船的阻力作为 的函数比无灯泡形式的阻力增加得更快。因此,灯泡船在大约 以上的平水优势几乎消失。在不规则波浪中,几乎所有的灯泡船在博福特 8 以上都有劣势。由于在北大西洋,风力强度超过博福特 8 的概率仅约为 10%,而在 之前,灯泡船在不考虑航行性能的情况下是最佳船只[20],因此灯泡设计可以仅考虑平水性能。
In navigation in ice, the bulbous bow has proved to be advantageous. Its form enables a tipping of ice floes coming from the front in such a way that they glide along the hull of the foreship with their wet-side friction coefficient, which is small. Due to this effect, the speed loss of a ship with a bulbous bow is smaller than that of a bulbless one. 在冰上航行时,球形船头被证明是有利的。它的形状使得来自前方的冰块能够倾斜,从而以较小的湿侧摩擦系数沿着前船的船体滑动。由于这一效应,球形船头的船只速度损失小于没有球形船头的船只。
If from the beginning a bulbous bow is included in the shaping of the underwater hull form, then for fast ships especially it is possible to leave the traditional recommendations on the fullness of the forebody and the unavoidable abaft position of the center of buoyancy. Without disadvantages, the bow bulb allows a fuller foreship form and therefore better trim and stability properties. Using an implicit bulb, a more slender aft-body is possible at constant total block coefficient with improved propulsive performance. Without increase of the resistance, a greater angle of entrance for the waterlines can be used as compared with the accepted practice so far [22]. 如果从一开始就将球形船首纳入水下船体形状的设计中,那么对于快速船只来说,尤其可以不再遵循传统的前体丰满度建议和不可避免的浮力中心位置在船尾的要求。船首球泡没有缺点,允许更丰满的前船体形状,从而改善了船的吃水和稳定性特性。使用隐式球泡,可以在保持总块系数不变的情况下实现更纤细的船尾,并提高推进性能。与迄今为止的公认做法相比,可以在不增加阻力的情况下使用更大的水线入水角度。
Resistance and bulb effect 电阻和灯泡效应
The most important effect of a bulbous bow is its influence on the different resistance components and consequently on the required power. Although the design charts represent the power reduction due to a bulb, for a better understanding the hydrodynamic phenomenon shall be discussed by means of the influence of the bulb on the resistance. For this purpose, the following subdivision of the total resistance is used 球形船首最重要的效果是它对不同阻力成分的影响,从而影响所需的功率。尽管设计图表显示了由于球形船首而导致的功率减少,但为了更好地理解,应该通过球形船首对阻力的影响来讨论水动力现象。为此,使用以下总阻力的细分。
where 哪里 viscous resistance 粘性阻力 frictional resistance 摩擦阻力 viscous residual resistance 粘性残余电阻 wavemaking resistance 波浪阻力 wave-breaking resistance 抗波破坏能力
The latter two components are related to wavemaking. Their contributions to the total resistance are very different for ships with different block coefficients and speeds. Here, an explanation is to be found for the fact that the resistance reduction due to a bulb for full, slow ships can exceed the wave resistance alone, which at is a negligible part of the total resistance. 后两个组成部分与造波有关。它们对总阻力的贡献在不同的船舶块系数和速度下差异很大。在这里,可以解释为什么对于满载、低速船舶,因球鼻而导致的阻力减少可以超过单独的波浪阻力,而在 时,波浪阻力在总阻力中占的比例微不足道。
The additional bulb surface always increases the frictional resistance , which is the main part of the viscous component . Up to now, it is not quite clear whether the bulb affects the viscous residual resistance due to the variation of the velocity field in the near bow range . But in the reanalysis of test data based on Froude's method, presented here, this open point is of no account. 额外的灯泡表面总是增加摩擦阻力 ,这是粘性成分的主要部分 。到目前为止,灯泡是否影响由于近船首范围内速度场的变化而产生的粘性残余阻力 尚不清楚。但在这里基于弗劳德方法重新分析的测试数据中,这一开放点并不重要。
There is no doubt concerning the influence of the bulbous bow on wavemaking resistance . The linearized theory of wave resistance has rendered the most important contribution to the clarification of this problem . According to this theory, the bulb problem is a pure interference problem of the free wave systems of the ship and the bulb. Depending on phase difference and amplitudes, a total mutual cancellation of both interfering wave systems may occur. The position of the bulb body causes the phase difference, while its volume is related to the amplitude. The wave resistance is evaluated by analysis of the free wave patterns measured in model experiments . 毫无疑问,球形船首对波浪阻力的影响 。线性化的波浪阻力理论对澄清这个问题做出了最重要的贡献 。根据这一理论,球形问题是船舶和球体自由波系统的纯干涉问题。根据相位差和振幅,两个干涉波系统可能会完全相互抵消。球体的位置造成相位差,而其体积与振幅相关。波浪阻力通过分析在模型实验中测得的自由波模式来评估 。
The wave-breaking resistance depends directly on the rising and development of free as well as local waves in the vicinity of forebody and is a question of typical spray phenomenon. Understanding of the breaking phenomenon of ship waves is important for the bulb design for full ships. includes all parts of the energy loss by the breaking of too-steep bow waves. The main part of this energy can be detected by wake measurements . The local wave system contributes the main part to this resistance component. This wave system consists mainly of the two back waves of bow and stern which are generated by deflection of the momentum. The deflection rate of the flow is a degree of the steepness of these back waves, of which only the bow wave is of a practical importance in bulb design. 波浪破坏阻力 直接依赖于船首附近自由波和局部波的上升和发展,是典型喷雾现象的问题。理解船舶波浪的破坏现象对全船的船首设计至关重要。 包括由于过陡船首波浪破坏而导致的所有能量损失部分。这部分能量的主要部分可以通过尾流测量 来检测。局部波浪系统对这一阻力分量贡献了主要部分。该波浪系统主要由船首和船尾的两个背波组成,这些背波是由动量偏转产生的。流动的偏转率是这些背波陡峭程度的一个指标,其中只有船首波在船首设计中具有实际重要性。
The wave-breaking resistance can be diminished only insofar as it is possible to prevent the breaking of bow waves. According to the reason of its creation, this is only possible by changing the deflection of momentum or the bow near the velocity field, respectively. In principle this may be achieved not only by a bulbous bow, but by suitable hydrofoils as well [29]. A theoretical treatment of the linearized problem has recently begun . 波浪破坏阻力只能在防止船首波破坏的情况下减小。根据其产生的原因,这只有通过改变动量的偏转或船首附近的速度场来实现。原则上,这不仅可以通过球形船首实现,还可以通过合适的水翼实现【29】。对线性化问题的理论处理最近开始了 。
The effect of the bulb on the different resistance components 灯泡对不同电阻元件的影响
can be discerned by taking the differences of the corresponding resistance components of the ship without (index ) and with bulb (index ): 可以通过取船只在没有(索引 )和有灯泡(索引 )情况下相应电阻组件的差异来辨别
Consequently it is possible to define three different bulb effects. In any case, a positive bulb effect means a resistance reduction, and vice versa. The two latter terms in equation (8) account for the primary bulb effect, which for bulb design are the most important. The difference of the wave resistances 因此,可以定义三种不同的灯泡效应。在任何情况下,正灯泡效应 意味着电阻降低,反之亦然。方程(8)中的后两个项考虑了主要的灯泡效应,这对于灯泡设计是最重要的。波阻抗的差异
is the interference effect, which is the sum of the interference resistance and the wave resistance of the bulb body alone. Its contribution to the total bulb effect can be estimated by an analysis of the interfering free wave patterns [26|. According to Froude's law, it can be scaled directly to the full-scale ship. Only for slender fast ships does it give the main proportion to the total bulb effect, where the amount depends essentially on the bulb volume and the sign on the longitudinal position of the bulb center. 干扰效应是干扰阻力 和灯泡本体的波阻力 之和。通过对干扰自由波模式的分析,可以估计其对总灯泡效应的贡献[26|。根据弗劳德定律,它可以直接缩放到全尺度船只。只有对于细长的快速船只,它才对总灯泡效应贡献主要比例,其数量主要取决于灯泡体积和灯泡中心的纵向位置符号。
The difference between the wave-breaking resistances 波浪破坏抗力的差异
is the breaking effect, which is the main contribution to the total bulb effect for full, slow ships. Its contribution is: the bigger the bulb, the better the deflection of the flow in the vicinity of the bow region. This means for the bulb form an optimal distributed bulb volume in the longitudinal direction to minimize gradients of the hull surface in the region of rising bow waves. Using geosim model tests, Taniguchi [12] and Baba [23] have shown that the wave-breaking resistance, and consequently the breaking effect, is Froude number dependent. 破浪效应是全速慢船总灯泡效应的主要贡献。其贡献是:灯泡越大,船头附近的水流偏转效果越好。这意味着灯泡形状在纵向上应形成最佳分布的灯泡体积,以最小化船体表面在上升波浪区域的梯度。通过地模拟模型测试,谷口[12]和巴巴[23]表明,破浪阻力,因此破浪效应,依赖于弗劳德数。
The difference between the viscous resistance parts 粘性阻力部分之间的差异
is the secondary bulb effect, which is of minor importance for the total bulb effect. Due to the larger surface of bulb ships, the frictional resistance term of equation (11) is always negative and diminishes the bulb action. For reasons mentioned before, the contribution of the difference of viscous residual resistance is not taken into account. 次级灯泡效应,对总灯泡效应的重要性较小。由于灯泡船的表面积较大,方程(11)中的摩擦阻力项始终为负,并减小了灯泡作用。由于之前提到的原因,粘性残余阻力差异的贡献未被考虑。
Finally, the question has to be answered whether equivalent variations of the ship may result in the same improvements as an addition of a bulb, for example, an increase of block coefficient corresponding to the bulb volume, or an elongation of the ship length corresponding to the bulb length . It has been shown by model experiments [14] and by linear theory [22] that the effect of a bulb cannot be achieved by form variations (9). 最后,必须回答的问题是,船舶的等效变化是否会产生与添加灯泡相同的改进,例如,增加与灯泡体积相对应的块系数 ,或增加与灯泡长度相对应的船舶长度 。模型实验[14]和线性理论[22]已经表明,灯泡的效果无法通过形状变化来实现(9)。
Influence of bulb parameters on bulb effect 灯泡参数对灯泡效应的影响
At constant Froude number , the bulb effect is a function of all six bulb parameters: 在恒定的弗劳德数 下,灯泡效应是所有六个灯泡参数的函数:
This multidimensional relationship complicates the understanding of the dependencies on single parameters, the knowledge of which is very helpful for bulb design. Unfortunately, a quantitative description of these dependencies is possible in only a few cases, because systematic model experiments are too expensive and some parameters cannot be varied independently. On the basis of linearized wave resistance theory, however, a qualitative picture can be developed, supported by special model experiments, for example, the wave cuts , which not only prove the tendency of the dependence. 这种多维关系使得对单一参数依赖性的理解变得复杂,而这些知识对灯泡设计非常有帮助。不幸的是,只有在少数情况下才能对这些依赖关系进行定量描述,因为系统的模型实验成本太高,并且某些参数无法独立变化。然而,基于线性化波阻力理论,可以发展出一个定性的图景,并通过特殊的模型实验来支持,例如波切 ,这些实验不仅证明了依赖关系的趋势。
Fig. 7 Dependence of interference and primary bulb effect on the length parameter . Comparison of theory and experiment with an elementary ship of the form [31] 图 7 干涉和主灯泡效应对长度参数 的依赖性。与形式为 的基本船舶的理论与实验比较[31]
Because of the doubts connected with the secondary bulb effect, the following consideration is confined to both parts of the primary effect only-to the interference and breaking effects, respectively. The relationship between the two and the magnitude of their contributions to the total bulb effect are not discussed at this stage. 由于与次级灯泡效应相关的疑虑,以下考虑仅限于主要效应的两个部分——干扰效应和破坏效应。此阶段不讨论两者之间的关系及其对总灯泡效应的贡献大小。
According to linearized theory, the interference effect depends on the volumetric parameter in a quadratic manner [32]. is a measure of the amplitude of the wave pattern. The breaking effect shows a similar dependence. With increasing bulb volume, both effects increase up to a maximum with a subsequent decrease. The optimal bulb volumes corresponding to the maximum values of the different bulb effects do not, in general, coincide. For the interference effect, the optimal volume can be estimated for a given ship-bulb combination by the wave cut method [26]. In a similar way, the interference effect depends on the breadth and cross-section parameter. 根据线性化理论,干扰效应以二次方式依赖于体积参数 [32]。 是波形幅度的度量。破坏效应显示出类似的依赖性。随着灯泡体积的增加,这两种效应都增加到最大值,然后随之减少。不同灯泡效应的最大值对应的最佳灯泡体积通常不重合。对于干扰效应,可以通过波切法[26]估算给定船舶-灯泡组合的最佳体积。以类似的方式,干扰效应依赖于宽度和横截面参数。
For a constant bulb volume and depth, the length parameter has a great influence on the interference effect. As it is a measure for the phase relation of the free wave systems of ship and bulb, typical maxima and minima appear as a direct consequence of the interfering waves. As shown in Fig. 7, this tendency is confirmed by model experiments [31]. The influence of the length parameter on the breaking effect can be caught intuitively by its mode of action. With increasing , this effect increases at first and after a maximum decreases monotonically to zero, due to the fact that the deflection of momentum in the vicinity of the bow is hardly altered by a very long cylindrical bulb. Because the lateral parameter is strongly related to the length parameter, its influence on the bulb effect is similar. 对于恒定的灯泡体积和深度,长度参数 对干扰效应有很大影响。由于它是船舶和灯泡自由波系统相位关系的度量,典型的极大值和极小值是干扰波的直接结果。如图 7 所示,这一趋势得到了模型实验的验证[31]。长度参数对破坏效应的影响可以通过其作用方式直观地理解。随着 的增加,这一效应最初增加,达到最大值后单调减少至零,因为在船头附近的动量偏转几乎不受非常长的圆柱形灯泡的影响。由于横向参数与长度参数密切相关,因此它对灯泡效应的影响也类似。
The dependence of the interference effect on the depth parameter is described simply by linear theory because the term of a spherical bulb coincides with the center of the sphere. If such a bulb of constant volume and longitudinal position is moved from infinite depth up to the water surface, the interferential effect increases at first monotonically from zero to a maximum, decreases subsequently, and finally becomes negative due to an increase of the resistance of the emerging bulb body. The breaking effect behaves similarly, but it can become positive again, if , as with the -type. In this case the behavior of a ship-bulb combination is similar to a longer main hull increased in length by . 干扰效应对深度参数 的依赖可以通过线性理论简单描述,因为球形灯泡的 项与球体的中心重合。如果这样的恒定体积和纵向位置的灯泡从无限深度移动到水面,干扰效应最初单调地从零增加到最大值,随后减少,最后由于浮出水面的灯泡体的阻力增加而变为负值。破坏效应表现得类似,但如果 ,如 型,它可以再次变为正值。在这种情况下,船舶-灯泡组合的行为类似于通过 增加长度的更长主船体。
Fig. 8 Optimal bulb volume of a ship-bulb combination as a function of Froude number . The prismatic coefficient of the elementary ship form is the parameter of the curves 图 8 船舶-灯泡组合的最佳灯泡体积 与弗劳德数 的关系。基本船型 的棱柱系数 是曲线的参数。
[31]
Flg. 9 Optimal bulb volume of a ship-bulb combination with as a function of Froude number . Depth position is the parameter of the curves [31] 图 9 船舶-灯泡组合的最佳灯泡体积 与 作为弗劳德数 的函数。深度位置 是曲线的参数[31]
Influence of ship main parameters on bulb size and bulb effect 船舶主要参数对船首灯大小和灯泡效应的影响
Linear theory permits comment on the influence of some ship main parameters on bulb size. The theoretical results relate to the interference effect only, but have general validity throughout and, in particular, are applicable to the breaking effect. For discussion, the most suitable case is the optimal bulb, which minimizes the wave resistance of a ship-bulb combination. With elementary ships of the form ( [31], it may be shown that an increased prismatic coefficient or block coefficient , respectively, is associated with increasing volume of the optimal spherical bulb. Figure 8 gives an impression of this fact. From this it follows, for ships with long parallel middlebody, that with increasing and decreasing , the optimal bulb volume increases (Yim [22], Fig. 4). The depth of the bulb has a similar influence. As shown in Fig. 9, at constant Froude number and longitudinal position, the optimal bulb volume increases with increasing depth position . Moreover, both figures clearly indicate the enormous influence of ship speed on optimal bulb volume, which increases in an undulating manner with increasing speed. These theoretical results are upper limits for the actual effects. While their absolute values are hardly of practical interest, the tendency of the dependence of bulb volume on speed, block coefficient, length of entrance, and bulb position is useful for the actual design. 线性理论允许对一些船舶主要参数对灯泡大小的影响进行评论。理论结果仅与干扰效应有关,但在整个范围内具有普遍有效性,特别适用于破坏效应。讨论中,最合适的案例是最优灯泡,它最小化船舶-灯泡组合的波阻力。对于形式为( [31])的基本船舶,可以证明,增加的棱柱系数 或块系数 分别与最优球形灯泡的体积增加相关。图 8 给出了这一事实的印象。因此,对于具有长平行中体的船舶,随着 的增加和 的减少,最优灯泡体积增加(Yim [22],图 4)。灯泡的深度也有类似的影响。如图 9 所示,在恒定的弗劳德数 和纵向位置下,最优灯泡体积随着深度位置 的增加而增加。此外,这两幅图清楚地表明了船速对最优灯泡体积的巨大影响,随着速度的增加,最优灯泡体积以波动的方式增加。 这些理论结果是实际效果的上限。虽然它们的绝对值几乎没有实际意义,但灯泡体积对速度、阻力系数、入口长度和灯泡位置的依赖趋势对实际设计是有用的。
Since the wave system is created only by the nonparallel part of the main hull, and in the real fluid the forebody makes the main contribution, the length of the parallel middlebody has hardly any influence on the bulb size and, therefore, the same holds for the length/beam ratio too. For ships with , the wavemaking resistance is only a function of , as shown by the upper limit curves in Fig. 10 (see also Baba [23], Fig. 10). The beam/draft ratio has a great influence on bulb effect, bulb size, and draft parameter (upper limit curves in Fig. 11). Consequently, for dimensioning of a bulbous bow, the main-hull parameters are , and . Unfortunately, in the preliminary design phase, , and often too, is unknown. Therefore, the following design guidelines are mainly based only on block coefficient and beam/draft ratio . 由于波浪系统仅由主船体的非平行部分创建,而在真实流体中,前体贡献最大,平行中体的长度 对船首灯泡的大小几乎没有影响,因此,长度/宽度比 也是如此。对于具有 的船舶,造波阻力仅是 的函数,如图 10 中的上限曲线所示(另见 Baba [23],图 10)。宽度/吃水比 对灯泡效应、灯泡大小和吃水参数 有很大影响(图 11 中的上限曲线)。因此,在灯泡船首的尺寸设计中,主船体参数是 和 。不幸的是,在初步设计阶段, ,而且通常 也是未知的。因此,以下设计指南主要仅基于块系数 和宽度/吃水比 。
Design guidelines for bulbous bows 球形船首设计指南
It is well known that the existing design methods, for example, the classical method by Taylor, are not sufficient for power estimation of a bulb ship and for modern bulb design. To fill this gap in the design guidelines, a large number of routine test results of ships without and with bulb, carried out by the two German model basins, have been reanalyzed in a research project. The design guidelines derived, the design charts, and a computer program have been successfully applied on various occasions. From the multitude of diagrams developed in this paper, only one example is depicted. For complete information, reference has to be made to FDS Bericht No. 36/1973|8] and VWS Bericht No. 811/78[38]. It is emphasized that the information content of the design diagrams cannot be better than that of the original data base, especially in the cases with very small data collection. 众所周知,现有的设计方法,例如泰勒的经典方法,无法满足灯泡船的功率估算和现代灯泡设计的需求。为了填补设计指南中的这一空白,德国的两个模型水池对没有灯泡和有灯泡的船只进行了大量常规测试结果的重新分析。所衍生的设计指南、设计图表和计算机程序已在多个场合成功应用。本文开发的众多图表中,仅展示了一个例子。有关完整信息,请参考 FDS Bericht No. 36/1973|8]和 VWS Bericht No. 811/78[38]。强调设计图表的信息内容不能优于原始数据库,特别是在数据收集非常少的情况下。
Reanalysis of routine test results 常规测试结果的重新分析
Since the bulbous bow affects primarily the wavemaking resistance, the design guidelines should correctly be related to the wave or residual resistance. During preparation of the research work, it became evident; however, that most of the usable data were propulsion rather than resistance test results. Since in principle it makes no difference whether the bulb effect is derived from resistance or propulsion tests, a power specific bulb effect, or power reduction factor, respectively, was defined: 由于球形船首主要影响造波阻力,设计指南应正确与波浪或残余阻力相关。在研究工作准备过程中,然而,显而易见的是,大多数可用数据是推进而非阻力测试结果。由于原则上球形效应是源于阻力还是推进测试并没有区别,因此定义了一个功率特定的球形效应或功率减少因子:
In this form the bulb effect is the power difference of the ship without and with bulb related to the power of the bulbless ship. According to this definition, a positive bulb effect corresponds to a power reduction, and vice versa. 在这种形式下,灯泡效应是指有无灯泡 和有灯泡 的船只的功率差异,与无灯泡船只的功率相关。根据这个定义,正的灯泡效应对应于功率减少,反之亦然。
In order to separate the different friction resistance components of ships without and with bulb in accordance with Froude's method, the total delivered power 为了根据弗劳德的方法分离没有和有球泡的船舶的不同摩擦阻力成分,总交付功率
is regarded as composed of a frictional part (index ) and a residual part (index ). If the propulsive efficiency is known, the residual power can be calculated as the difference 被认为由摩擦部分(索引 )和残余部分(索引 )组成。如果已知推进效率 ,则残余功率可以计算为两者的差值。
Fig. 10 Dependence of the residual power reduction coefficient on the length/beam ratio, the volumetric parameter, and the length parameter, respectively. Curve parameter is the Froude number. The parameters , , and are constant 图 10 残余功率减少系数对长度/梁比、体积参数和长度参数的依赖关系。曲线参数为弗劳德数。参数 、 和 为常数。
Fig. 11 Dependence of the residual power reduction coefficient on the beam/draft ratio, the volumetric parameter, and the depth parameter, respectively. Curve parameter is the Froude number. The parameters , 图 11 残余功率减少系数对波束/吃水比、体积参数和深度参数的依赖关系。曲线参数为弗劳德数。参数 , and are constant 和 是常量
between total and frictional power, and a residual power reduction factor 在总功率和摩擦功率之间,以及一个剩余功率减少因子
can be defined. 可以被定义。
The relationship between effective and delivered power is 有效 与输出功率之间的关系是
With the frictional power calculated by the International Towing Tank Conference (ITTC) 1957 line 根据国际拖曳水池会议(ITTC)1957 年线计算的摩擦力
the residual power is 剩余功率是
With equations (16) to (18), the residual power reduction factor becomes 通过方程(16)到(18),残余功率减少因子变为
A separation of the various bulb effects is not possible in this way. 以这种方式无法分离各种灯泡效果。
The propulsive efficiency is a function of hull form and speed and should be known for the analysis of the model test results. Moreover, for ships without and with bulb, the propulsive efficiencies are generally not equal, but it is in the beneficial speed range of the bulb ship. Unfortunately, from most of the propulsion test results, could not be estimated. Therefore, as a first step in simplification of the reanalysis, a constant has to be chosen for ships without and with bulb. The mistake is small if in the calculation of the residual power reduction factor by equation ( ), the condition is assumed. In general, the relations 推进效率 是船体形状和速度的函数,应该在模型试验结果分析中已知。此外,对于没有和有球鼻的船,推进效率通常不相等,但在球鼻船的有利速度范围内是 。不幸的是,从大多数推进试验结果中, 无法估计。因此,作为重新分析简化的第一步,必须为没有和有球鼻的船选择一个常数 。如果在通过方程( )计算剩余功率减少因子时假设条件 ,则错误很小。一般来说,关系
Fig. 12 Influence of different propulsive coefficients on the residual power reduction coefficient, shown with the ship-bulb combination No. 7 of Table 2 图 12 不同推进系数对剩余功率减少系数的影响,显示为表 2 中的船舶-灯泡组合第 7 号
Fig. 13 Comparison of the residual power reduction coefficients from full-scale and model-scale measurements (for main particulars, see Table 1) 图 13 全尺寸和模型尺寸测量的剩余功率减少系数比较(主要参数见表 1)
and 和
hold. Consequently the numerator difference of equation 保持。因此,方程的分子差异 is 是
but because of 但因为
it is 它是
Therefore, the residual power reduction factor used here is 因此,这里使用的剩余功率降低系数是
Because a few propulsive efficiencies are known only in the collected routine test results, in a second step of simplification an has to be defined that should be constant for all ship-bulb combinations within the whole range of block coefficient . From the scarce experimental results and practical experi- 由于一些推进效率仅在收集的常规测试结果中已知,在简化的第二步中,必须定义一个 ,该值应在整个块系数 范围内对所有船舶-灯泡组合保持不变。根据稀缺的实验结果和实际经验,
ence 翻译文本:意识
appeared to be a very good mean value. For normal ships, is between 0.6 and 0.8 . Therefore, it is important to test the consequences of divergence of from the mean value 0.7 on the residual power reduction coefficient . As shown in Fig. 12, a change in of percent affects at low Froude numbers, a change in of only percent; at higher 似乎是一个非常好的平均值。对于普通船舶, 在 0.6 和 0.8 之间。因此,测试 从平均值 0.7 偏离的后果对剩余功率减少系数 是很重要的。如图 12 所示, 的变化 百分比在低弗劳德数下影响 , 的变化仅为 百分比;在更高的 of only percent. 仅占 百分之。
Further analysis is facilitated by the introduction of dimensionless coefficients as follows. To eliminate influences of the ship hull form, the power displacment coefficient 进一步分析通过引入无量纲系数得以简化。为了消除船体形状的影响,功率排水系数
is chosen. This leads to a residual power coefficient 被选择。这导致了一个残余功率系数
and with friction law 和摩擦定律
to the bulb effect related to the residual power coefficient, that is, to the residual power reduction coefficient 与残余功率系数相关的灯泡效应,即残余功率降低系数
Finally, it should be mentioned that in the reanalysis a form factor is not considered. 最后,需要提到的是,在重新分析中未考虑形状因子 。
The residual power reduction coefficient can be scaled directly to full-scale ship. Figure 13 shows the results of measurements at ship [35] and model scale. The slight sea-wave influence on full-scale measurements is eliminated. That the amounts do not coincide totally might depend on the different trims of the forms without and with bulb. Table 1 gives the main particulars of the ships. In case 3, the delivered power of the bulbless ship is converted to a draft by aid of the Admiralty formula. 残余功率减少系数可以直接缩放到全尺度船舶。图 13 显示了船舶[35]和模型尺度的测量结果。全尺度测量中轻微的海浪影响被消除。数值不完全一致可能与无球头和有球头的船体不同的吃水有关。表 1 给出了船舶的主要参数。在案例 3 中,无球头船舶的交付功率通过海军公式转换为吃水 。
Design charts 设计图表
The analysis of the many experimental results is sorted out by -collectives in which many bulb ship forms with nearly the same block coefficients are collected. There are so many design charts that only the case of is presented here. The variation of the residual power reduction coefficient by equation (22) of each ship form 许多实验结果的分析由 -集体整理,其中收集了许多具有几乎相同阻力系数的灯泡船型。设计图表非常多,这里仅展示了 的情况。每种船型的残余功率减少系数的变化由方程(22)给出。
has been calculated and presented as a function of Froude number . The curve parameter is the bulb form (Fig. 14). From these curves it is possible to derive cross curves for all six bulb parameters, which are collected in Table 2 together with some other main parameters of the ship-bulb combinations. The derivation and fairing of these cross curves (Fig. 15-20) naturally are not totally without problems, because at only one variable bulb parameter the other five parameters are regarded as constant. This assumption is correct in only a few cases for some parameters; in most of the cases, all parameters alter simultaneously. Therefore, each diagram contains an upper limit curve which indicates the maximum possible improvement due to a bulb. Figures 21 and 22 show that the way of analysis and construction of design diagrams is justified. In these figures, theoretical and the corresponding experimental 已计算并作为弗劳德数 的函数呈现。曲线参数为灯泡形状(图 14)。从这些曲线中,可以推导出所有六个灯泡参数的交叉曲线,这些曲线与船舶-灯泡组合的其他主要参数一起收集在表 2 中。这些交叉曲线的推导和修整(图 15-20)自然并非没有问题,因为在只有一个可变灯泡参数的情况下,其他五个参数被视为常数。这个假设在某些参数的少数情况下是正确的;在大多数情况下,所有参数同时变化。因此,每个图表都包含一条上限曲线,指示灯泡可能带来的最大改进。图 21 和图 22 显示了分析和设计图构建的方法是合理的。在这些图中,理论与相应的实验结果。
Table 1 Main particulars of ships without (Ship 1) arti with bulbous . 表 1 无(船 1)人工舵与球鼻的船舶主要参数 。
bow. (See Fig. 13; is the related trim) 弓。(见图 13; 是相关的修整)
case 1 案例 1
case 2 案例 2
ship 1 船 1
ship 3 船 3
ship 1 船 1
ship 2 船 2
5,98
6,57
5,96
5,68
0,7842
0,7869
0,7813
0,8370
0,7857
0,7832
6,933
7,032
6,933
7,087
4,550
4,140
4,550
4,645
-
0,0205
-
0,0205
-
0,1337
-
0,1397
-
0,5570
-
0,6260
-
0,0946
-
0,0954
-
0,1056
-
0,1070
-
0,1725
-
0,1773
results which are evaluated in the same manner are compared [31|. Even if the optimistic theoretical results are not achieved in the experiments, the tendencies are at least represented correctly. 以相同方式评估的结果进行比较[31|。即使在实验中未能实现乐观的理论结果,趋势至少是正确反映的。
The diagrams of Figs. 16-20, which are derived from the 图 16-20 的图表源自于
Fig. 14 Residual power reduction coefficient of 14 ship-bulb combinations as a function of Froude number. Basic diagram for Figs. 15-20 (for main parameters, see Table 2). Curve parameter is the bulb form 图 14 14 种船舶灯泡组合的剩余功率减少系数与弗劳德数的关系。图 15-20 的基本图示(主要参数见表 2)。曲线参数为灯泡形状。
Table 2 Main parameters of ship-bulb combinations of the data collected with (see Fig. 14) 表 2 收集到的船舶-灯泡组合的主要参数 (见图 14)
Model 模型
1
2
3
4
5
6
7
8
9
10
11
12
13
14
8
0.6846
0.689
0.6891
0.6918
0,6924
0.6963
0.6967
0.6367
0.6970
0.7004
0.7033
0.7145
0.7227
0.726
WL
0.8173
0.8389
0.7762
0.8058
0.8449
0.7994
0 CM 0 厘米
0.9829
0.9868
0.8785
0.9938
0.9845
0.9916
0,9733
0.9733
0.9868
0.9920
0.9829
0.9949
0.9845
0.9816
0.6865
0.7211
0.6919
0.6994
0.7148
0.7234
0.7234
0.6703
0.6452
0.6662
0.6985
0.6994
06945
안 安
7.5489
6.088
5.293
6.4997
6.0061
5.702
6.094
6,094
7.2094
7.315
8.171
70
6.517
2.1539
3.006
3.153
28285
3.0402
2.972
3.114
3.114
22575
2.491
2.16
3.0402
2.724
LE/B
3.774
3.044
20472
24561
2855
2.978
2.978
3. 1634
2.907
3.5
50
61
2.514
0.6846
0.6935
0.6977
0.7069
0.7026
0.7055
0.7028
0.7062
0.7047
0.7070
0.7194
0.7
0.7317
/
3.774
2.244
3.4639
2.6587
3.063
3.240
3.197
3.4162
3.1100
3673
3.4
26
2.722
0.0370
0.0299
0.0433
0.0329
0.0330
0.0363
0.0440
0.0368
0.0381
00251
0.0258
0.03
96
0.0330
0.1554
0.0840
0.1762
0.1821
0.1798
0.1717
0.2091
0.1746
0.1538
0.1463
0.1351
0.18
0.1798
0.1734
0
0.6377
06580
0.5612
0.6730
0.9333
0.5
0.5
0.5852
0.5810
0.6309
30
0.9333
0.5652
0.1008
0.0465
0.1103
0.1056
0.1090
0.1035
0.1367
0.1061
0.1032
0.0956
0.0802
0.
0.1008
ABL
0.1829
0.1258
0.1286
0.1498
0.1516
0.1237
0.16
0.1284
0.1832
0.1096
0.1268
0.1230
0.1516
0.1157
0,3356
0.1350
0.4015
0.3929
0.3606
0.2871
0.5878
0.2975
%
2026
0.3782
0.6466
0.8712
0.3713
0.9071
1.2547
0.8
1.3183
0.6207
0.5177
2.0
0.6957
3.0572
1.4159
2.1905
3.0228
28112
3.0283
3.0692
24268
2.5054
2.3123
1.8757
2.6458
2.4545
. 375
Fig. 15 Maximum residual power reduction coefficient as a function of the volumetric parameter of total bulb volume (derived from Fig. 14) 图 15 最大剩余功率减少系数与总灯泡体积的体积参数的关系(来源于图 14)
Flg. 16 Residual power reduction coefficient as a function of the volumetric parameter (derived from Fig. 14). Curve parameter is the Froude number 图 16 残余功率减少系数与体积参数的关系(来源于图 14)。曲线参数为弗劳德数
Fig. 17 Residual power reduction coefficient as a function of the cross-section parameter (derived from Fig. 14). Curve parameter is the Froude number 图 17 残余功率减少系数与截面参数的关系(来源于图 14)。曲线参数为弗劳德数
Fig. 18 Residual power reduction coefficient as a function of the lateral parameter (derived from Fig. 14). Curve parameter is the Froude number 图 18 残余功率减少系数与横向参数的关系(来源于图 14)。曲线参数为弗劳德数
Fig. 19 Residual power reduction coefficient as a function of the length parameter (derived from Fig. 14). Curve parameter is the Froude number 图 19 残余功率减少系数与长度参数的关系(来源于图 14)。曲线参数为弗劳德数
Fig. 20 Residual power reduction coefficient as a function of the breadth parameter (derived from Fig. 14). Curve parameter is the Froude number 图 20 残余功率减少系数与宽度参数的关系(来源于图 14)。曲线参数为弗劳德数
diagram of Fig. 14 for , represent the correlations between bulb parameters and power gain. Regions may clearly be recognized in which certain bulb parameters are unfavorable and which are to be avoided. 图 14 的示意图 表示灯泡参数与功率增益之间的相关性。可以清楚地识别出某些灯泡参数不利的区域,以及应避免的区域。
The use of the diagrams follows from their derivation. Interpolations are permitted inside the parameter ranges shown, while extrapolations should be avoided. If the main dimensions of a ship are fixed and a bulb is to be fitted, then the estimation of bulb parameters and the power reduction due to this bulb is possible by means of the design charts of the corresponding block coefficient . For this purpose, only the main-hull particulars, , and as well as the Froude number , are required. For a given bulb parameter-which can be any of the six parameters-it is possible to read in the respective design chart at the curve of the known Froude number the residual power reduction factor . With this , the remaining bulb parameters are estimated in the other diagrams at the corresponding -curve. Except for the configuration of the bulbous forebody, the problem is solved, because, for constant, all six bulb parameters are assigned to a constant . 图表的使用源于它们的推导。在所示的参数范围内允许插值,而应避免外推。如果船舶的主要尺寸是固定的,并且要安装一个船首球泡,则可以通过相应的块系数设计图来估算球泡参数以及由于该球泡导致的功率减少。为此,仅需要主船体的详细信息、 和 以及弗劳德数 。对于给定的球泡参数——可以是六个参数中的任何一个——可以在已知弗劳德数 的曲线中读取相应设计图中的剩余功率减少系数 。有了这个 ,可以在其他图表中根据相应的 曲线估算剩余的球泡参数。除了球形前体的配置外,问题就解决了,因为对于 常数,所有六个球泡参数都与一个常数 相关联。
If , and of the bulbless ship are inside the ranges of the analyzed ship-bulb combinations, for example, of Table 2, then the residual power reduction factor yields the wanted residual power gain. If departures from the main-hull parameters appear, the is a good approximate value. Except for the beam/draft ratio, the influence of and deviations is small, so that a special correction is not necessary for these parameters. A general correction formula so far does not exist. 如果 ,并且无灯船的 在分析的船舶-灯泡组合的范围内,例如表 2,则剩余功率减少因子 产生所需的剩余功率增益。如果出现主船体参数的偏差, 是一个很好的近似值。除了宽度/吃水比, 和 的偏差影响较小,因此这些参数不需要特别修正。目前尚不存在通用的修正公式。
If the delivered power for the bulbless ship is known, then the required power of the bulb ship can be calculated by the following formula: 如果已知无灯船的交付功率,则可以通过以下公式计算灯船所需的功率:
where the residual power coefficient of the bulbless ship has to be estimated with according to equation (20). For unknown delivered power of the bulbless ship, in the project phase, the required power can be calculated by the following formula: 无灯船的残余功率系数 必须根据方程(20)与 进行估算。在项目阶段,对于无灯船的未知交付功率,可以通过以下公式计算所需功率:
Fig. 21 Bulb effect on residual or wave resistance coefficient, respectively, as a function of Froude number. Comparison of theoretical and experimental results of elementary ship form . Curve parameter is the volumetric parameter of the total bulb volume. The experimental results are evaluated with a form factor 图 21 灯泡对残余或波阻力系数的影响,分别作为弗劳德数的函数。基本船型的理论与实验结果比较 。曲线参数是总灯泡体积的体积参数。实验结果使用形状因子 进行评估。
Fig. 22 Bulb effect on residual or wave resistance, respectively, as a function of the volumetric parameter of the total bulb volume (derived from Fig. 21). Curve parameter is the Froude number 图 22 灯泡效应对残余或波动阻力的影响,分别作为总灯泡体积的体积参数的函数(来源于图 21)。曲线参数为弗劳德数
where can be estimated by one of the common procedures (for example, Taylor-Gertler [35], or Guldhammer [36]). 其中 可以通过常见的程序之一进行估计(例如,泰勒-格特勒 [35],或古尔德哈默 [36])。
If several bulb parameters are known (this includes also the judgment of a given bulb), then the estimation of the power gain by means of the diagrams is problematic, because the relation of the single values is hardly guaranteed in such a way that all known bulb parameters result in the same at constant Froude number. By using the volumetric parameter as the main parameter connected with a possible consideration of and , the diagrams can be used in such cases for bulb design or for a judgment. 如果已知多个灯泡参数(这也包括对给定灯泡的判断),那么通过图表估算功率增益是有问题的,因为单个值之间的关系很难保证,以至于所有已知的灯泡参数在恒定的弗劳德数下得出相同的 。通过使用体积参数 作为主要参数,并可能考虑 和 ,在这种情况下可以使用图表进行灯泡设计或判断。
It appears tempting to use the diagrams to design an optimal bulb by taking the parameters in accordance with their maximum reduction effect only. This procedure cannot be recommended, because all six optimal bulb parameters chosen in this way do not generally coincide with those of a concrete bulb of the analyzed test data 看起来仅根据最大减小效果的参数使用图表设计最佳灯泡是很诱人的。然而,这种做法不推荐,因为以这种方式选择的六个最佳灯泡参数通常与分析测试数据的具体灯泡参数不一致。
To judge the effect of a bulb change on the required power of a bulb ship, the diagrams can be used to assist in decisionmaking. By their aid, the tendency of parameter changing can be detected which an alteration of shape does or does not suggest. Even in their imperfect form, the design charts facilitate the decision for an application of a bulbous bow. But they do not substitute for the model test, because the actual power requirement for a project can be measured by experiment only. 为了判断更换灯泡对灯泡船所需功率的影响,可以使用图表来辅助决策。借助这些图表,可以检测到参数变化的趋势,而这种变化是否暗示形状的改变。即使在不完美的形式下,设计图表也有助于决定是否应用球形船头。但它们不能替代模型测试,因为项目的实际功率需求只能通过实验来测量。
From Figs. 23 to 26, the bulb parameters can be estimated if at first instance the power consumption is of no interest. These figures show the relationship of the different bulb parameters to each other for the ship-bulb forms which have been analyzed within the research project. The usual bulb parameter ranges are marked by upper and lower dotted lines. 从图 23 到图 26,如果初始情况下功耗不重要,可以估算灯泡参数。这些图显示了在研究项目中分析的船用灯泡形式中,不同灯泡参数之间的关系。通常的灯泡参数范围由上下虚线标出。
Aspects of bulb design 灯泡设计的各个方面
In the preceding sections, it has been shown that a welldimensioned bulbous bow improves the performance of a ship in many ways by smoothing the flow around the forebody and by reducing the wavemaking resistance. In a particular case, the decision for or against a bulbous bow is the matter of a cost-effectiveness analysis [11|, which is not the subject of this 在前面的章节中,已经显示出一个尺寸合理的球形船首通过平滑船体前部的水流和减少波浪阻力,能够在许多方面提高船舶的性能。在特定情况下,选择或不选择球形船首是一个成本效益分析的问题,这不是本文的主题。
paper. 纸。
In general it may be stated that a hydrodynamically good main hull with low wavemaking does not need a bulbous bow in any case. But ships with pronounced bad wavemaking should always be fitted with a bulb. Practical points of view will decide whether an additive or an implicit bulb is to be provided for. For ships already built, an additive bulb will in general be the best solution, while for a new design an implicit 一般来说,可以说一个水动力性能良好、波浪产生较少的主船体在任何情况下都不需要球鼻。然而,波浪产生明显不良的船只应始终配备球鼻。从实际的角度来看,将决定是提供附加球鼻还是隐式球鼻。对于已经建造的船只,附加球鼻通常是最佳解决方案,而对于新设计则是隐式球鼻。
bulb might be advantageous. 灯泡可能是有利的。
The shaping of a bulbous bow, that is, the longitudinal and depth distribution of the bulb volume in proportion to the bulb parameters, can be described only in a qualitative way. Although for a concrete longitudinal distribution of bulb volume, the knowledge of the wave pattern of the bulbless ship is an important decision-making aid, in the preliminary project phase this information is usually not available. But even without this information it is possible to indicate general guiding rules for shaping a bulbous bow. Essentially they are related to 船首球形的形成,即球形体积的纵向和深度分布与球形参数的比例,只能以定性方式描述。尽管对于具体的球形体积纵向分布,了解无球形船的波浪模式是一个重要的决策辅助工具,但在初步项目阶段,这些信息通常不可用。但即使没有这些信息,也可以指出一些关于形成船首球形的一般指导原则。基本上,它们与以下内容相关:
type of ship (full or slender), 船的类型(丰满或纤细),
service speed (slow or fast), 服务速度(慢或快),
frequency of draft alteration at FP (large draft variation or defined and ballast draft), and 在 FP 处草案修改的频率(大幅度草案变化或定义的 和压载草案),以及
main operation area of the ship (for example, with much heavy seaway or drift ice). 船舶的主要操作区域(例如,重浪或漂流冰较多的地方)。
A specific ship-bulb form shows optimum performance only at design conditions. At off-design conditions its performance may be poor. 一种特定的船舶灯泡形状仅在设计条件下表现出最佳性能。在非设计条件下,其性能可能较差。
For the distribution for the bulb volume, the following three rules are important: 对于灯泡体积的分布,以下三个规则很重要:
Deeply emerged volume is of little effect. 深度浸入的音量效果不大。
Longitudinally concentrated volume near to the free surface increases the interference effect. 靠近自由表面的纵向集中体积增加了干扰效应。
Longitudinally distributed volume near to the free surface influences the momentum deflection. 靠近自由表面的纵向分布体积影响动量偏转。
Fig. 23 Volumetric and depth parameter versus block coefficient 图 23 体积和深度参数与块系数的关系
Fig. 24 Length and breadth parameter versus volumetric parameter 图 24 长度和宽度参数与体积参数的关系
Fig. 25 Cross-section and lateral parameter versus volumetric parameter 图 25 横截面和侧向参数与体积参数的关系
Fig. 26 Total increase of the volume ( ) and the wetted surface of the main hull due to a bulbous bow versus volumetric coefficient 图 26 主船体因球鼻艏而导致的体积总增加( )和湿润表面 与体积系数 的关系
The waterlines of the bulb nose should be streamlined but not circular, in order to avoid separation |33|. 灯泡鼻的水线应流线型而非圆形,以避免分离 |33|。
For ships with a strong wavemaking tendency, the bulb volume should be concentrated in the longitudinal direction, where the upper part of the bulb body at the should not be located above the . The integration of bulb and ship can be straight-lined ( , Rule 4). The fairing volume plays a subordinate role. The maximum width of the bulb can be situated in front of the forward perpendicular. At such a bulbous bow it may happen, of course, that cavitation occurs. This problem is not treated here. 对于具有强烈造波倾向的船只,船首球泡的体积应集中在纵向方向,球泡体的上部在 处不应位于 之上。球泡与船体的结合可以是直线型( ,规则 4)。整流体积起到次要作用。球泡的最大宽度可以位于前垂线之前。在这样的球形船首上,当然可能会发生气蚀。这个问题在这里不作讨论。
For ships with much wave-breaking, the bulb volume should be distributed well in the longitudinal direction. The upper part of the bulb body can reach to the peak of the bow backwave of the bulbless ship [34]. A well-formed laterally and forward-inclined bulb ridge avoids the breaking of the bow back-wave. The fairing volume plays an important role. The upper part of the bulb should be faired well into main hull in order that the tail water of the bulb ridge interferes well with the remaining bow wave. In the lower part of the bulb, the waterlines should have small angles of entrance ii the bulb is to emerge high under ballast conditions. Due to the danger of separation in this area, the fairing of the waterlines should not be too hollow. 对于波浪破坏较大的船只,船首球泡的体积应在纵向上合理分布。球泡体的上部应达到无球泡船舶的船首回波的峰值。一个良好形成的横向和前倾的球泡脊可以避免船首回波的破坏。整流体积起着重要作用。球泡的上部应与主船体良好整流,以便球泡脊的尾水能够有效干扰剩余的船首波。在球泡的下部,水线的入水角度应较小,以便在压载条件下球泡能够高高浮出水面。由于该区域存在分离的危险,水线的整流不应过于凹陷。
Bulb-type recommendations 灯泡类型推荐
The O-type is suitable for full as well as for slender ships. It fits well with U-and V-types of foreship sections and offers space for sonar equipment. The lens-type should be chosen for ships which often operate in heavy seas, because it is less susceptable to slamming O 型适用于全船和细长船。它与 U 型和 V 型的船首部分相配,并为声纳设备提供空间。对于经常在恶劣海况下作业的船只,应选择透镜型,因为它对撞击的敏感性较低。
The -type is good for ships with large draft variations (tramp ships) and U-type foreship sections. The effect of the bulbous bow decreases with increasing draft, and vice versa; but in heavy seas the danger of slamming increases with decreasing draft. 型适用于吃水变化大的船舶(杂货船)和 U 型前船体部分。球鼻船首的效果随着吃水的增加而减小,反之亦然;但在恶劣海况下,吃水减少时碰撞的危险增加。
The -type can be provided for all ships with well-defined and ballast draft. It is easily faired into -shaped forebodies and has in general good seakeeping performance. In the fully submerged condition, its damping effect is very high. 型可为所有具有明确 和压载吃水的船舶提供。它可以轻松地与 形状的前体融合,并且通常具有良好的航行性能。在完全淹没的情况下,其阻尼效果非常高。
In all cases, the bulb should not emerge in the ballast condition so that its most forward point, B (Fig. 3), lies on the water surface. The individual resistance of the bulb body in this condition would be higher than its net efficiency. 在所有情况下,灯泡不应处于压舱状态,以便其最前端点 B(图 3)位于水面上。在这种情况下,灯泡本体的个体阻力将高于其净效率。
Summary 摘要
Today the bulbous bow has asserted itself as an elementary device in practical shipbuilding. But the existing design methods are not sufficient for power estimation of a bulb ship and for modern bulb design. A well-dimensioned bulb improves most of the properties of a ship. Therefore, qualitative and quantitative guiding rules are necessary for its beneficial application. 今天,球形船首已成为实用造船中的基本装置。但现有的设计方法不足以对球形船进行功率估算和现代球形设计。合理尺寸的球形船首可以改善船舶的大多数性能。因此,必须制定定性和定量的指导原则,以便其有效应用。
Compared with the indirect influence of a bulbous bow on thrust deduction and wake fraction, the bulb also influences directly the wake distribution in the propeller plane. Except for the strongly damped pitching motion, the bulb ship has the same seakeeping qualities as a bulbless ship up to Beaufort 6 . Therefore, regardless of seakeeping aspects, the bulb design may be carried out in view of the smooth-water performances only. In navigation in ice, the bulbous bow has proved to be advantageous. 与球形船首对推力扣除和尾流分数的间接影响相比,球形船首还直接影响螺旋桨平面的尾流分布。除了强阻尼的俯仰运动外,球形船在博福特 6 级以下具有与无球形船相同的航行性能。因此,无论是航行性能方面,球形设计都可以仅考虑平水性能。在冰区航行中,球形船首被证明是有利的。
The most important effect of a bulbous bow is its influence on the different resistance components and, consequently, on the required power consumption. By attenuation of the bow wave system, the bulb reduces the wavemaking as well as the wave-breaking resistance. 球形船首最重要的效果是它对不同阻力成分的影响,因此也影响所需的功率消耗。通过减弱船首波浪系统,球形船首减少了造波阻力和破浪阻力。
Two main bulb effects which are very important for bulb design are defined as the interference and the.breaking effects. The interference effect expresses the resistance change due to the interfering free wave systems of main hull and bulb. For slender, fast ships, it gives the main proportion to the total bulb effect. Its amount depends on bulb volume and the longitudinal position of the bulb center. The wave-breaking effect includes the energy loss by breaking of too steep bow waves and gives the main contribution to the total bulb effect of full, slow ships. Its amount depends on well-distributed bulb volume in the longitudinal direction. Both bulb effects are Froude number dependent. 两个主要的灯泡效应对灯泡设计非常重要,分别定义为干扰效应和破浪效应。干扰效应表示由于主船体和灯泡的干扰自由波系统导致的阻力变化。对于细长的快速船只,它对总灯泡效应的贡献占主要比例。其大小取决于灯泡体积和灯泡中心的纵向位置。破浪效应包括由于过于陡峭的船首波浪破裂而造成的能量损失,并对全速慢船的总灯泡效应贡献最大。其大小取决于纵向方向上灯泡体积的良好分布。这两种灯泡效应都与弗劳德数有关。
For bulb design, six bulb parameters are introduced, of which the volumetric, the cross-section, and the length parameter are the most important. The influence of bulb parameters on the different bulb effects is discussed in a qualitative manner, supported by the linearized theory of wave resistance and by some experimental results. This knowledge is important for the shaping of the bulb body according to the bulb parameters. 对于灯泡设计,引入了六个灯泡参数,其中体积、横截面和长度参数是最重要的。讨论了灯泡参数对不同灯泡效果的影响,采用定性方式,辅以波阻力的线性化理论和一些实验结果。这些知识对于根据灯泡参数塑造灯泡主体至关重要。
A quantitative design method is presented together with the necessary design data. The data are derived from an analysis of routine test results of the two German model basins. Most of the usable data were propulsion rather than resistance test results. Therefore, according to Froude's method, a residual power reduction coefficient is defined which can be scaled directly to the full-scale ship. The variation of this coefficient for each ship-bulb combination has been calculated and presented as a function of Froude number. From these curves the design charts are derived-for each bulb parameter, one diagram. From the multitude of diagrams, only one example is depicted. The calculation of the required power of the bulb ship is described. General guiding rules for shaping a bulbous bow are given. 提出了一种定量设计方法,并提供了必要的设计数据。这些数据来源于对两个德国模型水池常规测试结果的分析。大多数可用数据是推进而非阻力测试结果。因此,根据弗劳德方法,定义了一个残余功率减少系数,该系数可以直接缩放到全尺度船舶。计算并呈现了每个船舶-灯泡组合的该系数的变化,作为弗劳德数的函数。从这些曲线中导出了设计图表——每个灯泡参数一个图表。在众多图表中,仅展示了一个示例。描述了灯泡船所需功率的计算。给出了塑造灯泡船头的一般指导规则。
The design guidelines have been successfully applied on various occasions. 设计指南已成功应用于多个场合。
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35 Kerlen, H. and Petershagen, H., "Über den Einflu eines Bugwulstes auf Leistung und Geschwindigkeit eines völligen Frachtschiffes," HANSA, Vol. 105, No. 12, 1968, p. 1063-1067. 35 Kerlen, H. 和 Petershagen, H.,《关于船首突起对完全货船的性能和速度的影响》,HANSA,第 105 卷,第 12 期,1968 年,页 1063-1067。
36 Gertler, M., "A Reanalysis of the Original Test Data for the Taylor Standard Series," DTMB Report 806, 1954. 36 Gertler, M.,《泰勒标准系列原始测试数据的重新分析》,DTMB 报告 806,1954 年。
37 Guldhammer, H. E., and Harvald, Aa., Ship Resistance, Akademisk Forlag, Copenhagen, 1974 37 Guldhammer, H. E. 和 Harvald, Aa.,《船舶阻力》,学术出版社,哥本哈根,1974
38 Kracht, A.; "Weitere Untersuchungen über die Anwendung von Bugwülsten," VWS Bericht No. 811/78, Berlin, 1978. 38 Kracht, A.; "关于应用船舶舷侧的进一步研究," VWS 报告 No. 811/78, 柏林, 1978.
Discussion 讨论
Bohyun Yim, Member 林宝贤,成员
|The views expressed herein are the opinions of the discusser and not necessarily those of the Department of Defense or the Department of the Navy.] 本文所表达的观点是讨论者的意见,并不一定代表国防部或海军部的观点。
This paper has demonstrated clearly by experimental results from many ships that addition of a bulbous bow can reduce a large portion of the residual resistance of a ship. The charts with the approximate values of important design parameters for bulbous-bow ships will be very useful for naval architects. Although we know the mechanism of the bulb effect in the theory of wave resistance, the optimum size, shape, and location of the bulb cannot be obtained accurately because of the weakness in the theory of wave resistance. We all know well that the present linear theory cannot accurately predict the resistance of oceangoing ships. This is why experimental results are valuable in ship design. However, it is obvious that we have to make full use of theoretical knowledge in order to have a better design. 本文通过多艘船的实验结果清楚地表明,增加球鼻可以减少船舶的大部分残余阻力。关于球鼻船的重要设计参数的近似值图表将对船舶设计师非常有用。尽管我们在波浪阻力理论中知道球效应的机制,但由于波浪阻力理论的局限性,无法准确获得球的最佳大小、形状和位置。我们都知道,目前的线性理论无法准确预测远洋船舶的阻力。这就是实验结果在船舶设计中具有价值的原因。然而,显然我们必须充分利用理论知识,以便获得更好的设计。
In bulb design, we recognize that there are two types of bulb: doublet type and source type. The former reduces the sinecomponent of elementary ship waves while the latter reduces the cosine-component of elementary ship waves. Although normal ships with relatively large entrance angles have dominating sine waves which require the doublet-type bulb, there are ships with hollow waterlines which require the source-type bulb. That is, the bulb shape depends largely upon the waterline shape near the ship bow. I wonder whether this effect is reflected in the charts shown in the present paper? Block coefficient and Froude number are not enough to represent ship parameters related to bulb design. In this respect, Yim's 在船舶设计中,我们认识到有两种类型的船首灯泡:双重型和源型。前者减少了初级船波的正弦分量,而后者减少了初级船波的余弦分量。尽管正常船舶的入水角相对较大,主导的正弦波需要双重型灯泡,但也有一些船舶的水线是空心的,这需要源型灯泡。也就是说,灯泡的形状在很大程度上取决于船头附近的水线形状。我想知道这种影响是否在本文所示的图表中得到了反映?块系数和弗劳德数不足以代表与灯泡设计相关的船舶参数。在这方面,Yim 的
simple design method for a bulbous bow for a particular ship and design speed may be useful. 特定船舶和设计速度的球形船首简单设计方法可能会有用。
At the David W. Taylor Naval Ship R&D Center, several bulbs designed by Yim's method have been tested and satisfactory results obtained. Because the method uses linear theory, the computed bulb size is sometimes slightly larger than optimum, yet it gives very useful guidance. 在大卫·W·泰勒海军船舶研发中心,采用 Yim 方法设计的多个灯泡已进行测试,并获得了令人满意的结果。由于该方法使用线性理论,计算出的灯泡尺寸有时会略大于最佳尺寸,但它提供了非常有用的指导。
Eiichi Baba, Member 芭芭荣一,成员
The design charts of bulbous bows provided by the author are suitable especially for ships with relatively small block coefficients. For those ships, the wavemaking phenomena are influenced not only by the entrance part but also by the middle part and the run part, and the form effect on viscous resistance is relatively small. For full forms of , however, rather large viscous effects are included in the residual resistance component. Therefore, the scale effect is not taken into account in the author's charts. Further, as the author pointed out, for full forms the wavemaking phenomena are mainly depending on the entrance part. Therefore, the characteristic length for the expression of Froude number should be entrance length or ship beam instead of ship total length . The author says that at the preliminary design phase the entrance parameters and are unknown. However, if design charts for full forms based on the entrance parameters are provided, they may be effectively used in the preliminary design phase. Actually at Mitsubishi Heavy Industries a design method of full forms based on entrance parameters has been developed and since 1963 has served as a routine method as outlined in reference . Our design method for full forms is based on the following experimental and practical evidence derived from the analyses of towing test data of more than 200 full forms. 作者提供的球形船首设计图表特别适用于相对小的块系数的船舶。对于这些船舶,波浪产生现象不仅受到船首部分的影响,还受到中部和尾部的影响,且对粘性阻力的形状效应相对较小。然而,对于全形状的 ,残余阻力成分中包含相当大的粘性效应。因此,作者的图表中没有考虑尺度效应。此外,正如作者所指出的,对于全形状,波浪产生现象主要依赖于船首部分。因此,弗劳德数的特征长度应为船首长度 或船宽 ,而不是船总长度 。作者表示,在初步设计阶段,船首参数 和 是未知的。然而,如果提供基于船首参数的全形状设计图表,它们可以在初步设计阶段有效使用。 实际上,在三菱重工业,基于入口参数的全形状设计方法已经开发,并自 1963 年以来作为常规方法使用,如参考文献 所述。我们针对全形状的设计方法基于以下实验和实践证据,这些证据来自对 200 多个全形状的拖曳测试数据的分析。
For full forms with a 对于完整形式 与一个
VWS Berlin Model Basin, Berlin, Germany VWS 柏林模型水池,德国柏林 Numbers in brackets designate References at end of paper. 括号中的数字表示论文末尾的参考文献。
Presented at the Annual Meeting, New York, N. Y., November 16-18, 1978, of THE SOCIETY OF Naval. ARCHiteCTS and MarinE ENGINEERS. 在 1978 年 11 月 16 日至 18 日于纽约举行的海军建筑师和海洋工程师协会年会上发表。
Yim, Bohyun, "A Simple Design Theory and Method for Bulbous Bows of Ships," Journal of Ship Research, Vol. 18, No. 3, Sept. 1974, pp. . 任博贤, "船舶球形船首的简单设计理论与方法," 船舶研究杂志, 第 18 卷, 第 3 期, 1974 年 9 月, 第 页.