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June 11, 2009, 01:22 |
finding drag coefficient in laminar flow
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#1 |
New Member
kamal
Join Date: Jun 2009
Posts: 2
Rep Power: 0 |
hi all,
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. regards. Last edited by ksatpathy; June 11, 2009 at 01:28. Reason: to get more accurate idea |
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October 19, 2009, 12:46 |
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#2 |
Senior Member
Join Date: Oct 2009
Location: Germany
Posts: 636
Rep Power: 22 |
hi ksatpathy,
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. regards |
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October 22, 2009, 05:05 |
reply
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#3 |
New Member
kamal
Join Date: Jun 2009
Posts: 2
Rep Power: 0 |
thanks a lot mr.abdul for your kind information.
regards, satpathy. |
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January 14, 2010, 11:43 |
Question
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#4 |
New Member
Alexander Molero
Join Date: Jan 2010
Posts: 1
Rep Power: 0 |
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)?
Regards, Alex |
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