Dynamic mesh for a gearbox Sloshing

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  • Last Post 06 February 2020
Hosny456 posted this 05 February 2020

Hi, all
         I'm working on a GearBox sloshing, it consists of sun gear and 5 plantery gears
and ring gear, 
I do it as a 2D simulation and use dynamic mesh, the cells are all Tri, 
and for dynamic mesh I use Smoothing (Spring)
layering (ratio height)
and  re-meshing, (the default numbers) Local cell and region face

and for dynamic mesh zones, I used udf for the rotational motion and rigid body for all gear walls each alone
and I tried to add deforming for the interior and tried to do without, but the 2 cases generates negative cell after some time
I tried about all dynamic mesh options but usually I got a negative cell volume detection, after maybe 800 steps
my time step is 1e-6. 
my smallest element is 1 mm 
and the biggest is 20 mm
I used curvature and proximity, 
the rpm for the sun & Planetry gears are 8200 rpm
and for ring gear is 8200/3 rpm

usually after it gives my negative cell volume I use repair and improve mesh but it just work for few steps and fail again

So I have 3 questions:
1_is my mesh and dynamic mesh is correct?

2_ Now I was thinking is that possible if my mesh isn't valid any more can I import a mesh and import a Data for it?! 
meaning that keep the same velocities and other values but with a new mesh?

3_is there a way to know where is the position of negative cell elemetns?!

any help please!!

Thanks 


Overview of mesh 





Close look




Volume fraction of Oil when it gives me the error




Thanks in advance

rwoolhou posted this 06 February 2020

Check minimum sizing and speed v time step. Negative volume usually means something in the mesh passed through a cell in less than a time step so the mesh got turned inside out. In your case you could also have too few cells between some teeth. 

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