solution oscillating after few iterations

Saketh Bharadwaj · January 12, 2018, 09:40

I am trying to study flow around starship which has a complex geometry.

I am using k-epsilon model. "intensity and viscosity ratio" to initialise the turbulence model.

The solution started to oscillate after 100 iterations. When I tried to refine the mesh i see an error "intersecting surfaces".

I dont know what is the cause of the problem. I tried to implement few methods that were mentioned in the earlier posts...but nothing worked.

Can someone help me to get through this..?

thank you

fluid23 · January 15, 2018, 10:14

This is a steady solution, right? I would suspect that there would be a lot of flow separation on this which will dictate a transient approach. Your residuals don't look bad considering this, but if you want to get 'smooth' residuals you will need to probably switch from RANS to URANS and select a time step small enough to resolve whatever behavior that is driving your residuals into oscillation.

steve lee · March 11, 2018, 20:31

Hello.

I think there's exist very small gap in fluid region..

when you saw 'intersecting surfaces' error.
you should make more mesh in the small gap.. or modify geometry simply

January 15, 2018, 10:14		#2
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 17	This is a steady solution, right? I would suspect that there would be a lot of flow separation on this which will dictate a transient approach. Your residuals don't look bad considering this, but if you want to get 'smooth' residuals you will need to probably switch from RANS to URANS and select a time step small enough to resolve whatever behavior that is driving your residuals into oscillation. AliE likes this.

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March 11, 2018, 20:31		#3
steve lee Member Steve Join Date: Mar 2018 Location: South Korea Posts: 69 Rep Power: 8	Hello. I think there's exist very small gap in fluid region.. when you saw 'intersecting surfaces' error. you should make more mesh in the small gap.. or modify geometry simply