automatic time step control problem

Hello,

I have a problem with the use of the automatic time step control.
I am modelling an 2 dimensional vertical unsaturated problem with steady flow and transient heat transport.
There is a steady recharge on atmospheric boundary and a time series for heat transport.
If automatic time step control is chosen, the flow of water in the unsaturated area isn´t computed correctly.
The results are unrealistic high hydraulic heads. Using constant time steps (1d) for the whole problem or only steady resp. transient ( time series of recharge) modelling of the flow problem results in realistic data of hydraulic heads.
So what can I do using the automatic time step control for combined flow and heat transport?
Thanks for responses.

Falk

Is the model (maybe by mistake) density-dependent or with varying viscosity? Then the time-stepping might have an influence on the resulting heads - even with steady-state flow. Otherwise I would like to ask you to send the model to support@dhi-wasy.de (up to 10 MB) for checking.

Peter

Hi,

thanks for the answer.
All density and viscosity effects are on default settings.

Falk