Author Topic: why are my particle tracks so short when the injection velocity is low?  (Read 1258 times)

Offline pitney1

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When using CFX 10.0 Solver why are my particle tracks so short when the injection velocity is low? The Particle Fate Diagnostics indicate "Exceeded time limit".

Offline william

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The reason could be the value for the parameter Maximum Particle Integration Time Step.

SOLVER CONTROL:
PARTICLE CONTROL:
PARTICLE INTEGRATION:
Maximum Particle Integration Time Step = x s
END
END
END


The time step is automatically calculated from the ratio of a length scale (element edge length) over the particle velocity. So when the particle velocity is very small, the time step will be very large. By default the maximum limit on this parameter is also very large at 1.e+10s. So there is a chance that the time step can exceed the maximum tracking time hence the diagnostic about exceeding the time limit.

So the solution is to specify a smaller value for the Maximum Particle Integration Time Step. We would recommend basing this on the edge length of an element and the fluid velocity.