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Ansys Learning Forum Forums Discuss Simulation Fluids non-physical negative uds concentrations with small diffusion coefficient Reply To: non-physical negative uds concentrations with small diffusion coefficient

Rob
Forum Moderator

Scalars can be harder to converge, but I've run similar cases without problems. Setting diffusivity to zero does tend to cause problems, so it's not something I'd generally recommend. The value should be around the species diffusivity/density. 

Are the problem areas near any sink/source regions or flow boundaries?Â