numerical oscillations in flow parameters

alimea · October 30, 2018, 10:08

Hi all

I simulate transient incompressible creep flow on a couple of cylinders to calculate drag force in a special period of time. The drag coeff. oscillates with time (figure) and I don't know why!
Re=1, dt=0.005(Cr=0.8), SIMPLE algorithm, tolerances are set on 1e-12, URFs=0.5, 2nd order schemes are used for divergence terms and time derivative.

I think it is because of Mesh, but I don't know if it is correct or not and how I should improve it.

Thenks

pete20r2 · October 30, 2018, 11:44

Can you share the case or at least log file?

alimea · November 1, 2018, 12:23

Quote:

Originally Posted by pete20r2

Can you share the case or at least log file?

Thanks for your reply.

Unfortunately the project is not for me!
I didn't save the log file, but I can give you every information you need.

Regards

October 30, 2018, 10:08	numerical oscillations in flow parameters	#1
alimea Senior Member A. Min Join Date: Mar 2015 Posts: 308 Rep Power: 12	Hi all I simulate transient incompressible creep flow on a couple of cylinders to calculate drag force in a special period of time. The drag coeff. oscillates with time (figure) and I don't know why! Re=1, dt=0.005(Cr=0.8), SIMPLE algorithm, tolerances are set on 1e-12, URFs=0.5, 2nd order schemes are used for divergence terms and time derivative. I think it is because of Mesh, but I don't know if it is correct or not and how I should improve it. Thenks

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October 30, 2018, 11:44		#2
pete20r2 Senior Member Peter Baskovich Join Date: Jul 2014 Posts: 127 Rep Power: 12	Can you share the case or at least log file?