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Old   May 30, 2012, 09:40
Default Backward Facing Step
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L.M. Yang
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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
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Old   May 30, 2012, 14:39
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Peter Galimutti
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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
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Old   May 30, 2012, 21:03
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L.M. Yang
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Quote:
Originally Posted by p.galimutti View Post
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
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Old   May 31, 2012, 08:35
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Andrew
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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.
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Old   May 31, 2012, 10:29
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L.M. Yang
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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.
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