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-   -   Negative Volume during Mesh Motion Analysis (http://www.cfd-online.com/Forums/fluent/86435-negative-volume-during-mesh-motion-analysis.html)

giov_ingr March 22, 2011 16:46

Negative Volume during Mesh Motion Analysis
 
Hello,
I am working on 2D micro-eolic system. The model used is 6DOF with smoothing and remeshing enabled for the deforming zone. I would know if is correct to create the domain in this way:
An outer square surface (set as fluid and stationary) with an inner circle surface (set as fluid and deforming) trimmed of the wings shapes (the edges are set as rigid body).
The mesh between outer and inner surface is non conformal.
The problem is that varying the parameters of smoothing and remeshing, when the mesh motion starts, at the second step fluent shows

Updating mesh to time 2.00000e-01 (step = 00002)...
Info: 6DOF: can't compute angular acceleration.
Check moments/products of inertia.
Warning: negative volume detected --> repeat smoothing!
Warning: negative volume detected --> repeat smoothing!
Warning: negative volume detected --> repeat smoothing!

WARNING: non-positive volumes exist.

Dynamic Mesh Statistics:
Minimum Volume =-1.92535e-004
Maximum Volume =4.54192e-003
Maximum Cell Skew =1.16169e+000 (cell zone 3)
Warning: maximum cell skewness exceeds 0.95.
Warning: negative cell volume detected!
Error: Update dynamic mesh failed. Negative cell volume detected.
Error Object: ()

Could you help me about the non-positive volume and the angular acceleration?

Thank you

Centurion2011 December 12, 2013 05:39

try refining you mesh or lowering timestep

PNSK December 13, 2013 07:09

negative volume after some time steps
 
I was working I.C. engine piston movement. I got that negative volume error after some time steps i.e at 220 crank angle now what i have to do can any one help me
and also another error "face does not belong to cell"


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