Boundary conditions for fluid flow

In summary, the general boundary conditions for nonviscous, incompressible fluid flow include the no-slip boundary condition. This means that the fluid velocity at the surface of a sphere with uniform incident velocity will not be zero, but it will be zero at the surface of an infinite plane. This is in accordance with the solution for magnetostatics, where the continuity of B-perp is implied by the condition div B = 0, and the same can be said for v-perp in the case of div v = 0. However, for fluid flow, the radial velocity at the surface of a sphere does not vanish, as shown by the equation v_r = U cos\theta (1 - \frac{a^
  • #1
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What are the general boundary conditions for nonviscous, incompressible fluid flow? I am trying to find the velocity of fluid at the surface of a sphere with the incident fluid having uniform velocity. I am surprised to find in the solution that the radial velocity at the surface does not vanish. For magnetostatics, div B = 0 implies B-perp is continuous. Would not div v= 0 imply the same for v-perp?
What about the same problem but incident upon an infinite plane? Would the velocity not vanish at the surface?
 
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  • #2
I gather you are asking about the no-slip boundary condition?
 
  • #3
From Fluid Mechanics by Frank M. White

[tex]\psi = -\frac{1}{2} U r^2 sin^2 \theta + \frac{\lambda}{r} sin^2\theta[/tex]

[tex]\psi = 0 => r = a = (\frac{2\lambda}{U})^{1/3}[/tex]

[tex] v_r = -\frac{1}{r^2 sin\theta} \frac{\partial \psi}{\partial \theta} [/tex]

[tex] v_r = U cos\theta (1 - \frac{a^3}{r^3})[/tex]

so the radial component does appear to vanish at the surface [tex] r = a [/tex]
 

1. What are boundary conditions for fluid flow?

Boundary conditions for fluid flow are the set of conditions that define the behavior of a fluid at the boundaries of a system. They include variables such as pressure, temperature, and velocity, and they are used to solve equations that describe the motion of fluids.

2. Why are boundary conditions important for studying fluid flow?

Boundary conditions are important because they allow us to accurately model and predict the behavior of fluids in different systems. They help us understand how fluids will behave at the edges of a system, and how that behavior will impact the overall flow.

3. How do you determine the appropriate boundary conditions for a specific fluid flow problem?

The appropriate boundary conditions for a specific fluid flow problem can be determined by considering the physical properties of the fluid, the geometry of the system, and the desired outcomes of the problem. It may also involve conducting experiments or using numerical simulations to validate the chosen boundary conditions.

4. Can boundary conditions change during fluid flow?

Yes, boundary conditions can change during fluid flow. This could occur if there are changes in the system, such as a change in the properties of the fluid or a change in the geometry of the system. In some cases, boundary conditions may also be intentionally altered to study the effects on the fluid flow.

5. What happens if the boundary conditions are not properly defined?

If the boundary conditions are not properly defined, the results of the fluid flow problem may be inaccurate or even meaningless. This could lead to incorrect predictions and conclusions about the behavior of the fluid in the system. Therefore, it is important to carefully consider and define the boundary conditions when studying fluid flow.

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