Boundary condition when moving wall without pressure dropse

Schaum · April 19, 2019, 05:31

Goodmorning everyone,
I have a problem setting up the boundary conditions of my simulation.
The simulation consists in representing the motion of the fluid between two parallel walls, one of which is moving at a fixed speed and the other is stationary.
I'm trying to evaluate the effect that changes to the geometry of the two walls generate to the pressure profile.
The problem arises because at the inlet and the outlet the pressure must be zero (relative pressure) and solving the simulation, stationary with incompressible fluid, generates a pressure difference (fictitious) to justify the motion of the fluid.
The question then is how can the movement of the wall be defined as the unique cause of fluid motion and not a difference in pressure between inlet and outlet?

I hope I was clear enough and I thank in advance anyone who wanted to help me.

Sincerely
Schaum

2538sukham · September 7, 2021, 02:38

I think if it is walls then giving a zeroGradient might solve the issue. In other words, the wall gives the back the same reaction of any force on it by the fluid. So i think zeroGradient should work fine.

April 19, 2019, 05:31	Boundary condition when moving wall without pressure dropse	#1
Schaum New Member Krzysztof Join Date: Apr 2019 Location: Poland Posts: 1 Rep Power: 0	Goodmorning everyone, I have a problem setting up the boundary conditions of my simulation. The simulation consists in representing the motion of the fluid between two parallel walls, one of which is moving at a fixed speed and the other is stationary. I'm trying to evaluate the effect that changes to the geometry of the two walls generate to the pressure profile. The problem arises because at the inlet and the outlet the pressure must be zero (relative pressure) and solving the simulation, stationary with incompressible fluid, generates a pressure difference (fictitious) to justify the motion of the fluid. The question then is how can the movement of the wall be defined as the unique cause of fluid motion and not a difference in pressure between inlet and outlet? I hope I was clear enough and I thank in advance anyone who wanted to help me. Sincerely Schaum

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September 7, 2021, 02:38		#2
2538sukham Member Michael Sukham Join Date: Mar 2020 Location: India Posts: 85 Rep Power: 6	I think if it is walls then giving a zeroGradient might solve the issue. In other words, the wall gives the back the same reaction of any force on it by the fluid. So i think zeroGradient should work fine.