Backward Facing Step

LBMer_Young · May 30, 2012, 09:40

Hi, guys
I am simulating the laminar backward facing step with a 2D incompressible CFD code. Could any of you direct me how to set the inlet and outlet boundary conditions? The velocity profile of inlet boundary have been obtained. However, how do I set the pressure of inlet boundary and pressure and velocity of outlet boundary?

With kind regards,
Laman Yang

p.galimutti · May 30, 2012, 14:39

Since you already have a velocity profile, you do not need to set any inlet pressure. Pressure is implicit calculation based on velocity.

At the outlet 1 atm pressure can be given!

BTW, you said you are using code, so giving boundary conditions is specific to that code and check the manual on how to define b.cs

LBMer_Young · May 30, 2012, 21:03

Quote:

Originally Posted by p.galimutti

Since you already have a velocity profile, you do not need to set any inlet pressure. Pressure is implicit calculation based on velocity.

At the outlet 1 atm pressure can be given!

BTW, you said you are using code, so giving boundary conditions is specific to that code and check the manual on how to define b.cs

Hi, Peter
Thanks for you comments. Actually, the code is developed by myself. In this code, the conventional Navier-Stokes equation is solved rather than its incompressible forms (e.g. governing equation for artificial compressibility method and pre-conditioning method). So, in the inlet boundary there are three characteristics enter and one leaves the physical domain, i.e., the pressure in b.c need to extrapolate from the interior of the physical domain. My confusion is how to calculate the pressure. Similarly, the velocities in outlet b.c need to extrapolate from the interior of the physical domain. How could I evaluate the velocities in outlet b.c.

regards

mettler · May 31, 2012, 08:35

have you thought about transforming your equations to the streamline-vorticity equations? that way your pressure term drops out, and the bc's are pretty straight forward.

LBMer_Young · May 31, 2012, 10:29

Thanks for your advice. However, the flux solver in my code is developed by lattice Boltzmann method and the governing equation is the conventional Navier-Stokes equation. It is harder to transform the governing equation.

May 30, 2012, 09:40	Backward Facing Step	#1
LBMer_Young New Member L.M. Yang Join Date: Oct 2011 Posts: 9 Rep Power: 14	Hi, guys I am simulating the laminar backward facing step with a 2D incompressible CFD code. Could any of you direct me how to set the inlet and outlet boundary conditions? The velocity profile of inlet boundary have been obtained. However, how do I set the pressure of inlet boundary and pressure and velocity of outlet boundary? With kind regards, Laman Yang

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
How to write k and epsilon before the abnormal end	xiuying	OpenFOAM Running, Solving & CFD	8	August 27, 2013 15:33
Backward facing step.	Fluids	Main CFD Forum	7	December 4, 2012 11:28
Upgraded from Karmic Koala 9.10 to Lucid Lynx10.04.3	bookie56	OpenFOAM Installation	8	August 13, 2011 04:03
IcoFoam parallel woes	msrinath80	OpenFOAM Running, Solving & CFD	9	July 22, 2007 02:58
Could anybody help me see this error and give help	liugx212	OpenFOAM Running, Solving & CFD	3	January 4, 2006 18:07

May 30, 2012, 14:39		#2
p.galimutti Member Peter Galimutti Join Date: May 2012 Posts: 37 Rep Power: 13	Since you already have a velocity profile, you do not need to set any inlet pressure. Pressure is implicit calculation based on velocity. At the outlet 1 atm pressure can be given! BTW, you said you are using code, so giving boundary conditions is specific to that code and check the manual on how to define b.cs

May 31, 2012, 08:35		#4
mettler Senior Member Andrew Join Date: Mar 2009 Location: Washington, DC Posts: 209 Rep Power: 18	have you thought about transforming your equations to the streamline-vorticity equations? that way your pressure term drops out, and the bc's are pretty straight forward.

May 31, 2012, 10:29		#5
LBMer_Young New Member L.M. Yang Join Date: Oct 2011 Posts: 9 Rep Power: 14	Thanks for your advice. However, the flux solver in my code is developed by lattice Boltzmann method and the governing equation is the conventional Navier-Stokes equation. It is harder to transform the governing equation.