Boundary Conditions problem

o_mars_2010 · June 27, 2013, 07:00

I have developed a code to solve 2D Navier stokes equation in a channel.
I have used Immersed boundary method to simulate the vibration of a cantilever beam in the channel.
The problem is that i do not know the direction of flow.
So i can not specifiy which boundary to be inlet and which boundary to be outlet.
Thus, i have to set both of the boundary to be Open Boundary.
My question is:
Waht should be the pressure and velocity boundary conditions on both boundaries ???
Please Help me.

mxinfernal · July 8, 2013, 03:04

I assume that any flow created is going to be due to the vibration of the beam -- hence the open channel.

In that case,

jj = 1:ny
u(1,jj) = u(2,jj)
u(nx,jj) = u(nx-1,jj)

You get the idea.

o_mars_2010 · July 8, 2013, 03:10

i applied neumann boundary conditions for velocity
Dirichlet boundary conditions for pressure
P_inlet=0
p_outlet=0
The code works very well.

However, when i change the P_outlet to have a value for example 2 Pascal
the code fails and blow up.

Do you have any suggestions ??

June 27, 2013, 07:00	Boundary Conditions problem	#1
o_mars_2010 Member Osman Join Date: Oct 2012 Location: Japan Posts: 53 Rep Power: 14	I have developed a code to solve 2D Navier stokes equation in a channel. I have used Immersed boundary method to simulate the vibration of a cantilever beam in the channel. The problem is that i do not know the direction of flow. So i can not specifiy which boundary to be inlet and which boundary to be outlet. Thus, i have to set both of the boundary to be Open Boundary. My question is: Waht should be the pressure and velocity boundary conditions on both boundaries ??? Please Help me.

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July 8, 2013, 03:04		#2
mxinfernal New Member Join Date: Jun 2013 Posts: 1 Rep Power: 0	I assume that any flow created is going to be due to the vibration of the beam -- hence the open channel. In that case, jj = 1:ny u(1,jj) = u(2,jj) u(nx,jj) = u(nx-1,jj) You get the idea.

July 8, 2013, 03:10		#3
o_mars_2010 Member Osman Join Date: Oct 2012 Location: Japan Posts: 53 Rep Power: 14	i applied neumann boundary conditions for velocity Dirichlet boundary conditions for pressure P_inlet=0 p_outlet=0 The code works very well. However, when i change the P_outlet to have a value for example 2 Pascal the code fails and blow up. Do you have any suggestions ??