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June 29, 2013, 20:08 |
getting wrong value of drag
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#1 | |
Member
shiv
Join Date: Jun 2012
Location: Lucknow, IN
Posts: 51
Rep Power: 13 |
Hi openfoamers,
I am simulating a 3d flow around a sphere enclosed in a large cube, but problem is that i am getting my drag =1.04 instead of expt. drag =0.66 for reynolds no. of 300, parameters: fluid:air with rho=1.2, nu=1e-04, dia. of sphere=1m, velocity at inlet=0.03m/s ; Can someone please suggest what i am doing wrong. my controldict where drag lib parameters given : Quote:
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June 29, 2013, 20:45 |
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#2 |
Senior Member
Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,208
Rep Power: 26 |
what does vortices look like?is there any?
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Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked. |
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June 30, 2013, 16:28 |
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#3 |
Member
shiv
Join Date: Jun 2012
Location: Lucknow, IN
Posts: 51
Rep Power: 13 |
Hi Ehsan,
you pointed out correctly, i donot know why i am not getting the double threaded vortices for Re =300 thou with similar settings i have got as expected karman vortex street in 2d case. Got any ideas whats wrong when i am using 3d geometry?? |
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June 30, 2013, 16:43 |
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#4 |
Senior Member
Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,208
Rep Power: 26 |
Hi Shiv
are you using a turbulent model?which?how-Re or low-Re?
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Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked. |
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June 30, 2013, 17:22 |
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#5 |
Member
shiv
Join Date: Jun 2012
Location: Lucknow, IN
Posts: 51
Rep Power: 13 |
no, i am using icofoam solver so its laminar flow.
Ehsan, i noted something that when i use [nu=1e-04, U=0.03, Re=300] i am not getting vortices though when i use [nu=0.01, U=3, Re=300] i am getting vortices , both the cases have same Re why variation in results |
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July 1, 2013, 11:26 |
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#6 |
Senior Member
Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,208
Rep Power: 26 |
its unsteady if wakes there are.maybe deltaT isn't low enough.
__________________
Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked. |
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