2.Momentum Transport and Laminar Flow of Newtonian Fluids 2.牛顿流体的动量传输和层流
(1)Explanation of terms (1)术语解释
Laminar flow:Flow is regarded as being the unidirectional movement of lamellae of fluid sliding over one another,with no macroscopic mixing or intermingling of the fluid in the radial direction. 层流:流动被视为流体层在相互滑动时的单向运动,且在径向上没有宏观混合或交融
Turbulent flow:In contrast to laminar flow,the fluid undergoes chaotic fluctuations,leading to intense mixing both in the axial direction and in the radial direction. 湍流:与层流相反,流体经历混乱的波动,导致在轴向和径向上都发生强烈的混合
tau\tau-----viscous shear or momentum flux, Pa tau\tau -----粘性剪切或动量通量,Pa mu\mu-----dynamic viscosity,Pa's mu\mu -----动态粘度,Pa·s
c.iviomentum Transport and Laminar Flow of Newtonian Fluids c.牛顿流体的动量传输和层流
1)Explanation of terms 1)术语解释
Newton's law of viscosity:rarr"tau_(yx)=-mu(dv_(x))/(dy)"Longrightarrow{:[" Momentum transport is driven by "],[" velocity gradient."]:}\xrightarrow{\tau_{y x}=-\mu \frac{d v_{x}}{d y}} \Longrightarrow \begin{aligned} & \text { Momentum transport is driven by } \\ & \text { velocity gradient.}\end{aligned} 牛顿粘度定律: rarr"tau_(yx)=-mu(dv_(x))/(dy)"Longrightarrow{:[" Momentum transport is driven by "],[" velocity gradient."]:}\xrightarrow{\tau_{y x}=-\mu \frac{d v_{x}}{d y}} \Longrightarrow \begin{aligned} & \text { Momentum transport is driven by } \\ & \text { velocity gradient.}\end{aligned}.
Reynolds number: 雷诺数:
{:[Re=(D xxV_(2x8)xx rho)/(eta)],[=((" characteristic length ")xx(" average velocity ")xx(" density "))/((" viscosity "))],[(F_(g))/(F_(eta))=(rhoL^(2)V_(xz)^(2))/(etaV_(vzz)L)=(rho LV_( bar(xz)))/(eta)=Re=(" Inertial force ")/(" Viscous force ")]:}\begin{aligned}
& \operatorname{Re}=\frac{D \times V_{2 x 8} \times \rho}{\eta} \\
& =\frac{(\text { characteristic length }) \times(\text { average velocity }) \times(\text { density })}{(\text { viscosity })} \\
& \frac{F_{\mathrm{g}}}{F_{\eta}}=\frac{\rho L^{2} V_{x z}^{2}}{\eta V_{\mathrm{vzz}} L}=\frac{\rho L V_{\overline{x z}}}{\eta}=\mathrm{Re}=\frac{\text { Inertial force }}{\text { Viscous force }}
\end{aligned}
The viscosity of a gas is independent of the pressure of the gas and is a linear function of the square root of temperature. 气体的粘度与气体的压力无关,并且是温度平方根的线性函数
2.Momentum Transport and Laminar Flow of Newtonian Fluids 2.牛顿流体的动量传输和层流
(2)Analytical solutions (2)解析解
Momentum balance based on a control volume(steady-state,constant density and viscosity) 基于控制体的动量平衡(稳态,恒定密度和粘度)
R Rate == Flux xx\times Area R 速率 == 通量 xx\times 面积 ◻\square Momentum includes convective momentum and viscous momentum ◻\square 动量包括对流动量和粘性动量 ◻\square Forces include pressure and gravity ◻\square 力包括压力和重力
-Couette flow -库埃特流
-Fluid flow between two parallel flat plates -两个平行平板之间的流体流动
-Fluid flow down an inclined plane -流体在倾斜平面上的流动
-Fluid flow in a cylindrical tube -圆柱管中的流体流动
Momentum Transport(Summary) 动量传输(摘要)
2.Momentum Transport and Laminar Flow of Newtonian Fluids 2.牛顿流体的动量传输和层流
2)Analytical solutions 2)解析解 ◻\square Couette flow ◻\square 库埃特流
c.iviumentum Transport and Laminar Flow of Newtonian Fluids c.iviumentum 纽顿流体的运输和层流
2)Analytical solutions 2)解析解
-Fluid flow down an inclined plane -流体在倾斜平面上的流动
{:[v_(x)=(rho g cos theta)/(2mu)(delta^(2)-y^(2))],[tau_(yx)=-mu(dv_(x))/(dy)]}tau_(yz)=rho gy cos theta\left.\begin{array}{l}
v_{x}=\frac{\rho g \cos \theta}{2 \mu}\left(\delta^{2}-y^{2}\right) \\
\tau_{y x}=-\mu \frac{d v_{x}}{d y}
\end{array}\right\} \tau_{y z}=\rho g y \cos \theta
v_(x,max)=v_(x)|_(y-0)=(rho g cos theta)/(2mu)delta^(2)v_{x, m a x}=\left.v_{x}\right|_{y-0}=\frac{\rho g \cos \theta}{2 \mu} \delta^{2} bar(v)_(x)=(2)/(3)v_(x,max)=(rho g cos theta)/(3mu)delta^(2)\bar{v}_{x}=\frac{2}{3} v_{x, m a x}=\frac{\rho g \cos \theta}{3 \mu} \delta^{2}
2.Momentum Transport and Laminar Flow of Newtonian Fluids 2.牛顿流体的动量传输和层流
(2)Analytical solutions (2)解析解
Fluid flow in a cylindrical tube(fully developed flow) 圆柱管中的流体流动(完全发展流动)
2)Analytical solutions 2)解析解
Couette
flow 库埃特流动
Fluid flow between two parallel flat plates 两个平行平板之间的流体流动
{:[v_(x)=(V)/(Y)y],[tau_(mu)=-mu(V)/(Y)],[v_(x,mx)=V quadv_(z=0)=(Delta P)/(2mu L)delta^(2)],[ bar(v)_(x)=(2)/(3)v_(x)=],[ bar(v)_(z)=(1)/(2)v_(z)= bar(x)],[nu_(x)=(Delta P)/(2mu L)(delta^(2)-y^(2))],[v_(z)=(rho G cos theta)/(2mu)(delta^(2)-y^(2))],[v_(z)=((Delta P)/(L)+-rho g cos theta)((R^(2)-r^(2))/(4mu))],[tau_(yz)=(Delta P)/(L)y],[tau_(yz)=rho gy cos theta],[tau_(r)=((Delta P)/(L)+-rho g cos theta)((r)/(2))],[v_(x=pi)=(rho g cos theta)/(2mu)delta^(2)],[v_(z=)=((Delta P)/(L)+-rho g cos theta)((R^(2))/(4mu))],[ bar(v)_(x)=(2)/(3)v_(z)=],[ bar(v)_(z)=(1)/(2)v_(z=)]:}\begin{aligned}
& v_{x}=\frac{V}{Y} y \\
& \tau_{\mu}=-\mu \frac{V}{Y} \\
& v_{x, m x}=V \quad v_{z=0}=\frac{\Delta P}{2 \mu L} \delta^{2} \\
& \bar{v}_{\mathrm{x}}=\frac{2}{3} v_{\mathrm{x}}= \\
& \bar{v}_{\mathrm{z}}=\frac{1}{2} v_{\mathrm{z}}=\bar{x} \\
& \nu_{x}=\frac{\Delta P}{2 \mu L}\left(\delta^{2}-y^{2}\right) \\
& v_{z}=\frac{\rho G \cos \theta}{2 \mu}\left(\delta^{2}-y^{2}\right) \\
& v_{z}=\left(\frac{\Delta P}{L} \pm \rho g \cos \theta\right) \frac{R^{2}-r^{2}}{4 \mu} \\
& \tau_{y z}=\frac{\Delta P}{L} y \\
& \tau_{y z}=\rho g y \cos \theta \\
& \tau_{r}=\left(\frac{\Delta P}{L} \pm \rho g \cos \theta\right) \frac{r}{2} \\
& v_{x=\pi}=\frac{\rho g \cos \theta}{2 \mu} \delta^{2} \\
& v_{z=}=\left(\frac{\Delta P}{L} \pm \rho g \cos \theta\right) \frac{R^{2}}{4 \mu} \\
& \bar{v}_{x}=\frac{2}{3} v_{z}= \\
& \bar{v}_{z}=\frac{1}{2} v_{z=}
\end{aligned}
3.Equations of Continuity and Conservation of Momentum and Fluid Flow Past Submerged Objects 3.连续性方程、动量守恒方程及流体流过沉没物体的流动
1)Explanation of terms 1)术语解释
Incompressible fluid:A fluid that has constant density( rho=\rho= const.) 不可压缩流体:一种具有恒定密度( rho=\rho= const.)的流体
Entry length at entrance to a pipe:The distance a flow travels after entering a pipe before the flow becomes fully developed. 管道入口的入口长度:流体进入管道后在流动完全发展之前流动的距离