Summary: Smooth localized regions of velocity instability.
Flag
Check_Velocity_Distribution n
n = 0: off
n > 0: on
Description
Use this flag for simulations with marginal stability. Its primary purpose is to eliminate very small "pockets" of excessively high velocity magnitude caused by numerical instability.
The argument, n, multiplied by 0.1, is the percent of nodes that are eliminated per sweep. For example, for a model with 1 million nodes and n = 1, the algorithm eliminates up to 1000 nodes per sweep. If there are fewer than 1000 nodes with a spiking velocity, these velocities get smoothed.
This flag is most useful for compressible and some rotating applications that may be prone to divergence.
A reason not to enable the flag is if the model actually does have very small regions of high velocity flow. The flag may damp the result, and reduce the physically correct velocity values. Note that a fine mesh in the high velocity region reduces the damping because of the imposed limit (n).
An implication on accuracy is that peak velocities may be under-predicted. A value on n = 1 is safe for most analyses. n = 5 can produce results in which the peak velocities are under-predicted.
There are situations in which n = 5 is necessary. They include the application types described above, and others that exhibit localized regions of velocity that are incorrectly higher in value than surrounding regions.