Force calculation help
I have set up an SST flow to simulate the air flow around an underground train. With these settings I am trying to calculate the drag coefficient of the train but when I do an expression to calculate the force on the train then it keeps giving me a value of zero. The train is only moving at 15 m/s so i know the force will be low but zero seems a little extreme.
Is there a really obvious reason why it is doing this? All help is highly appreciated Thanks Tom 
Could you post your expression for the drag coeff?

i was going to work out the drag coefficient in excel later i just needed ansys to measure the drag force so that I can incorporate it into my equation
Thanks 
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The only value i need out of ansys is the value for the force acting on the body in the same direction as the air flow (i.e. the drag force) using this value I can then use:
Cd = (2Fd)/(density*velocity*velocity*area) 
Yes, that's the expression for the drag coeff, but I asked about your expression for the force (that apparently becomes zero...)
Is is something like: force_x()@some_area? Or its equivalent areaInt_X(Pressure)@some_area+areaInt(Wall Shear X)@some_area 
oh right sorry, miscommunication there
Yes that is what my equation looks like using x because that is the direction of flow and the area is front (because that is the domain that is on the front of my train) Thanks 
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I haven't checked the pressure integrals but looking at the force on the surface of the whole body it has given me a reasonable looking results :D
Thanks for your help Tom Walker 
train moving in tunnel help
hello
i am working on train moving in tunnel. i am getting floating error:invalid number. can any one help me. my email is sheikhnasir39@gmail.com plz help me thanks :confused: 
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