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Employee
Joey.X
Posts: 259
Registered: ‎06-14-2010

Re: How to find the drag on a 3d Body?

11-09-2011 02:04 PM in reply to: timothyatwell

Consistent unit is the location to check.  

Also looking at the solution convergence, velocity and pressure patterns/range. 

Can't tell anything else at this point except checking at the model details. Probally you can post some pictures. 

Jianhui Xie, Ph.D
Principal Engineer
MFG-Digital Simulation
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Contributor
timothyatwell
Posts: 14
Registered: ‎11-07-2011

Re: How to find the drag on a 3d Body?

11-09-2011 04:14 PM in reply to: Joey.X

here are some pics...

 

Getting those out of wack values constantly...

 

what is the convergence thing you was telling me about?

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Employee
Joey.X
Posts: 259
Registered: ‎06-14-2010

Re: How to find the drag on a 3d Body?

11-09-2011 05:00 PM in reply to: timothyatwell

 Thanks for posting the result screen pictures, the velocity and pressure pattern look good to me, but the magnitude appears big if the fluid media is air.  Here are more clues to check

(1) Fluid properties (density, viscosity etc.) 

(2) In acquiring total reaction force, make sure the selection for the nodes on the object surface only, no extra nodes involved.

(3) If this is unsteady  fluid flow analysis, change it to steady state, or have the final time long enough if keep doing unsteady analysis.

(4) Current mesh density appears coarse, use finer mesh and suggest using boundary layer mesh, this may increase your model size(DOFs), try these to have better accurate result if your computation resource allows. 



Jianhui Xie, Ph.D
Principal Engineer
MFG-Digital Simulation
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Contributor
timothyatwell
Posts: 14
Registered: ‎11-07-2011

Re: How to find the drag on a 3d Body?

11-10-2011 10:22 AM in reply to: Joey.X

Well, i began to get a little better results after continuously trying, however MP began to crash my computer, and  now it no longer wnats to mesh or anything. I managed to get this picture before tho.

 

Thanks for all your help Joey.X

 

I shall continue to do iterations once i get MP back up and running properly. 

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