decomposePar change the result?
 

Hi

I'm thying to solve the turbulent flow for a open channel using the LESModel oneEqEddy. I created a rectangular box with wallFunctions at the three fixed walls, rigid lid at the open surface and cyclic conditions at the ends, to simulate a infinitely long channel.
The flow is driven by a pressure gradient anded in pimpleFoam UEqn.C

tmp<fvVectorMatrix> UEqn
(
fvm::ddt(U)
+ fvm::div(phi, U)
+ GradPz
+ turbulence->divDevReff(U)
);

dimensionedVector GradPz
(
"GradPz", p.dimensions()/dimLength,vector(0.0,0.0,0.0)
);

scalar SlopeGradPz
(
readScalar(transportProperties.lookup("SlopeGradPz "))
);

The strange thing is that the result changes when I change the the number of processors in the decomposeDict, and that the result of a 100 long channel calculated by 4 processors, gives the same average flow as a 25 long of one processor. The strange thing is that a 100 long channel on 5 processors is the same as a 20 long, but not the same 100 long of 4 processors. The SlopeGradPz is the same for all four cases.

My ddtSheme type is steadyState and the end time in both cases are 350 with deltaT of 0.1.

How can I make sure that the result is not influenced by the decomposition of the problem?

Solved
 

The endTime was not enough... the stability was fin each processor and the average the result just created a picture of 4 x 25 meter or 5 x 20 meter, but extending the time to 1000, the two 100 meter channels turned out the same result.