BCs in a Tunnel Modeling

mehdi8619 · February 15, 2011, 16:14

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,

red_lemon · February 16, 2011, 18:54

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!

February 15, 2011, 16:14	BCs in a Tunnel Modeling	#1
mehdi8619 New Member Mehdi Famouri Join Date: Jan 2011 Posts: 12 Rep Power: 15	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.

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February 16, 2011, 18:54		#2
red_lemon New Member Join Date: Mar 2010 Posts: 18 Rep Power: 16	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!