Design of Bulbous Bows  球形船首的设计

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

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 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 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。

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