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Old   July 7, 2013, 05:05
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Sumit Yadav
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Originally Posted by Thomas P. Abraham
Hello Everyone:

I am trying to get the flow field over a car. I am having some trouble in understanding certain boundary conditions. The problem is as follows:

The flow is incompressible I have a computational mesh over the surface of the car. I could apply velocity boundary condition at the inlet and pressure boundary condition at the outlet (I will make sure the exit length is long enough to make this boundary condition valid). I will apply wall boundary condition at the bottom.

I have problem in understanding the rest of the boundary conditions. I have been recommended to use symmetry boundary conditions on the sides and the top. I know that when symmetry boundary condition is applied, the gradient across that boundary is zero. It acts as a mirror. This does not answer my question completely. My question is: What it physically means? Does it help to reduce the near wall effects?

All your insights and advise is appreciated, Thomas
Hi Everyone,

I am also performing the similar kind of simulation (I am simulating and underwater vehicle which is ejecting gases out form its nose/mouth). I am not able to recognize which boundary condition i should use at the nose/mouth of my vehicle so that it can eject gases out while it is moving forward in sea.

{From relative motion analysis, I am keeping my vehicle stationary but moving fluid (seawater) exactly opposite in the direction, my vehicle was supposed to move in}

@Yung-Ming Chen- Moving object volume should be less then 5% of the computation domain. (This assumption produces the almost similar to the reality)
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