Hello,

When I am trying to simulate a engineering model, after i write the geometry file and problem file , I get this error:

ERROR #006 *** DIFFERENCE BETWEEN STAGNATION PRESSURE AND STATIC PRESSURE AT REGION 21 NEGATIVE.

TRY TO LOWER RELAX. FACT. FOR PRESSURE AND/OR VELOCITIES.

why is this error as I have given stagnation conditions.

How can I get rid of this error and run my model successfully?

Thanks,

Arnab

The error means that the static pressure at the stagnation boundary (which is taken from the neighbouring cell) is higher than the stagnation pressure which you are trying to impose. This is unphysical. Check your initial and boundary conditions. If these are correct, under-relax more.

Hello,

I know that the initial conditions are correct.

How do i under relax more? what are the commands?? or where in GUI is the option to under relax pressure and velocities more??

I cannot find them..

Arnab

Assuming it's a steayd-state simulation, you can change the under-relaxation in Analysis Controls -> Solution Controls -> Equation Behavior -> Primary Variables. In the Solver Parameters tab you then have the under-relaxation factors - try reducing the ones for momentum and pressure. There are some guidelines in the User Guide on strategies for this.

Hello,

My simulation is unsteady(Transient). I dont know how to change the under relaxation factors for pressure and/or velocities.

I hope someone knows the method and guides me.

Thanks in advance,

Arnab

algo piso node 20 0.15 0.5

or

analysis control -> solution control -> solution method

Thanks John and Richard, but still I am getting the errors.

to underrelax the model more I have used

algo piso node 20 0.25 0.01

But I get the same error again. My delta time is of the order of 1.e^-6 and so I guess the analysis controls and the time step controls for this transient case is correct.

Do we necesaarily need to have initial conditoins mentioned in ufile for my simulation?

And if yes, then is there any way other than user-subroutine for initialising the model using GUI for transient case?

Can someone give me some other clues as to why I am getting this error and How can I get rid of it??

ERROR #006 *** DIFFERENCE BETWEEN STAGNATION PRESSURE AND STATIC PRESSURE AT REGION 21 NEGATIVE.

TRY TO LOWER RELAX. FACT. FOR PRESSURE AND/OR VELOCITIES.

Thanks,

Arnab