# BCs in a Tunnel Modeling

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 February 15, 2011, 16:14 BCs in a Tunnel Modeling #1 New Member   Mehdi Famouri Join Date: Jan 2011 Posts: 12 Rep Power: 6 Hi everyone, I’m trying to study the velocity distribution next to the uppermost part of a car tunnel. The problem has been described below (I know this not a precise modeling, but all I need is a rough estimation). Here is the BCs I applied: AA: 1- Moving wall (L=50 m, V=17.6 m/s) 2- Pressure-Inlet 3- Fixed wall 4- Pressure-Outlet BB: 1- Moving wall (L=100 m, V=17.6 m/s) 2- Pressure-Inlet 3- Fixed wall 4- Pressure-Outlet CC: 1- Moving wall (L=50 m, V=17.6 m/s) 2- Pressure-Inlet 3- Fixed wall 4- Outlet-vent DD: 1- Moving wall (L=50 m, V=17.6 m/s) 2- Pressure-Inlet 3- Fixed wall 4- Outflow The results are not similar, neither make sense! BTW, I solved both steady and unsteady. Also Turbulence (k-epsilon) modeling has been used. I’m not sure about 2 and 4 boundaries. Does any one know what the best BCs are? and here is the Computational Domain with the BCs: Thanks in Advance, Last edited by mehdi8619; February 15, 2011 at 18:57.

 February 16, 2011, 18:54 #2 New Member   Join Date: Mar 2010 Posts: 18 Rep Power: 7 Correct boundary conditions are 1 - ground - moving wall at 17.6m/s 2 - outlet - pressure outlet 0Pa gauge 3 - roof - moving wall at 17.6m/s 4 - velocity inlet at 17.6m/s assumes: >you are modelling car in an actual tunnel and not wind tunnel which has fixed relative walls >domain is large enough to allow turbulence profile to establish before impacting vehicle >upper boundary is the actual roof and not domain cut off in which case it should be symmetry >Note that wheels need MRF zones >Ensure you use prisms on car if possible and have high density wake region captured behind Hope that helps!

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