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2-D Laminar steady state simulation of backward facing step fails to provide accurate results

Question asked by Enrique Angola on Nov 4, 2016
Latest reply on Nov 6, 2016 by Bill McEachern



I am trying to perform a well known simulation of a 2-D Laminar steady state Re = 389 flow over a backward-facing-step. I tried the simulation in another software using the following boundary conditions:


1) Inlet vel = 0.544 m/s

    pressure gradient = 0

2) Outlet pressure = Atmospheric pressure

    Vel. gradient = 0

3) no slip walls


Using a standard quadrilateral mesh of 50,000 total cells with mesh refinements around the step I got very accurate results when comparing with experimental data.


Then I tried performing the same simulation on Solidworks FlowSim and results were off. On Solidworks I am using the same model for the channel, and I generated a very similar mesh. Boundary conditions on the 2-D simulation were the following:


1) Inlet velocity = 0.544 m/s
   check box: fully developed flow

2) Pressure outlet: set static pressure to atmospheric pressure (101300 Pa in this case)

3) Ideal walls


On my model I have a very long channel before the step, so I expect to see the usual parabolic 2-D channel velocity profile, but I don't. I see  a parabolic profile at the inlet which becomes completely linear around the middle of the channel on the way to the step. When I plot the velocity profile right before the step, and right after the step, the results are far from experimental results and/or my other simulation.

Is there anything I am not setting up properly on my simulation on FlowSim? I even tried doing mesh refinements on the walls, but results stay the same.


Thank you