finding drag coefficient in laminar flow
i am doing the flow analysis across a cylinder (2d laminar flow).i am facing the problem in calculating the drag coefficient.it is not matching (whatever the value comes from the erd file in star-cd)with the analytical result.
i have few doubts.
1.whether the erd file is valid only for turbulent case
2.what is the definition of tx,tyforce in the erd file in star-cd an how to get cd and cl from tx and ty force.
3.whether any other method is there in calclation of drag coeff.
a little bit late, but maybe it will help anyway. maybe there's some other user searching the forum...
1) erd-file should be valid for laminar and turbulent flow
2) the erd-file looks like sx, sy, sz, nx, ny, nz, tx, ty, tz with
sx = shear force in x-direction
nx = normal force in x-direction
tx = total force in x-direction
other directions accordingly
directions according to coordinate sys 1 in pro-star
calculate the lift and drag coefficients like you would do it in the analytical calculation. i think, you have used the formula to get the analytical solution.
3) i don's know any other methods
maybe your solution differs from the analytical solution, because it is a unsteady problem. there will be a karman vortex street behind the cylinder. the seperating vortices will cause a oscillation of the forces, while you're looking on just one value (printed in the erd-file).
try a transient simulation and repeate the calculation with the time averaged values.
thanks a lot mr.abdul for your kind information.
Can you help me to find drag coefficients in laminar flow to irregular shape (Underwater Vehicle)? Any book or Paper (in this mean, teorically)? And if i can use the model 3D-CAD (generated in Wildfire Pro-Engineering) in CFX-Post (in this mean, estimated)?
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