Periodicity

Sam

Hi,

I am solving an unsteady problem of flow in a tube subject to a periodic body force. The Reynold numbers are high so I have to use a turbulence model. If we denote the period of the body force as T, then although the problem is run forever, it never reaches a periodic state of period T. It may be periodic, but I am not able to determine what the period is.

This problem only occurs when the turbulence model is on. When I run at a very low Reynolds number without a turbulence model (by setting the viscosity high) the results are strictly periodic with period T.

Is this to be expected or do I have a bug somewhere ? How can I know that the initial transient is over and I have reached the stationary solution ?

Thanks !

Sam