TUFLOW Message 2583: Difference between revisions
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|type=[[WARNING]]
|message_desc=The Wu eddy viscosity formulation is based on bed friction velocity, which in turn is dependent on manning's number. High manning's numbers produce very high viscosity values, which in turn can limit the model timestep through the diffusion or Peclet number (reported as “Nd” in the HPC output). In general, in areas where very high manning's numbers are used (for example the slowing effect of buildings may be represented as increased surface roughness), the flow velocity is much slower and the elevated viscosity has little effect, other than to slow the simulation down. An upper limit to the manning's number used in the Wu viscosity calculation was introduced in the 2023-03-AA release to limit the computed viscosity in regions of unusually high roughness. Note that this only affects the viscosity calculation, the momentum equation will continue to use the original roughness value (or lookup table) as defined in the materials file. This warning message indicates that one or more of the manning's values used exceed the limit imposed for Wu viscosity calculation. The default limit is 0.1.
|suggestions=Consider if the use of materials with manning's in excess of 0.1 is really required. If it is required, then the it is possible to increase the limit used in the Wu viscosity calculation with the
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