[kishpishar]

Hello FOAMers,


I am trying to model the flow in a polymer treatment tank with a relatively simple geometry - essentially a rectangular apparatus in which the liquid enters through two large pipes fitted on the two opposite walls. Both the pipes are also bifurcated (before the main entrance to the tank) by means of an auxiliary pipe to send a portion of the main pipe's flow to the top portion of the tank. See the attached figures.

I noticed that using realizable k-epsilon model to simulate the tank results in a strange and unusual residual behavior. After about 80 iterations, the turbulent kinetic energy (k) residual drops all of a sudden to very low levels and k equation is not solved further. Beyond this point, the residuals of all other quantities continues to drop in the usual gradual, steady manner.

I feel that this behavior is not physical and the "converged solution" is not accurate because the k eqn. is not solved together with other quantities. Have anyone experienced such a behavior with the realizable k-epsilon model? What can I do to overcome this problem?

The problem doesn't seem related to the mesh - mesh check returns with all the usual quality parameters within their allowed limits. Here is the case attached. Steps to reproduce:

> blockMesh
> surfaceFeatureExtract
> snappyHexMesh -overwrite
> simpleFoam > log

I appreciate help from anyone.


-Kumar