[FlyingCat]

Hello everybody,


I ran the tutorial offSetCylinder with OpenFOAM-7 and I do not understand the results.



Without changing any parameter, the solution at the first time step (0.001 s) is given in the attached figure. This could be correct with simpleFoam but I ran pimpleFoam.


According to the simulation, the flow crosses the whole domain in 1 ms. This does not depend on the time step (1e-6 yields the same result).


If I change the boundary condition on the left from Neumann to Dirichlet on the pressure (P=0), then the flow slowly propagates, which better represents reality. But enforcing two Dirichlet boundary conditions on the pressure and velocity on the same boundary leads to oscillations of both variables.


I think this is a numerical issue since enforcing zero Neumann condition on the pressure should not yield a infinitely fast propagation of the flow. Does someone have an idea about this matter ?


Thank you

[FlyingCat]

Hello,


Could the problem be a known mathematical behaviour (that I do not know) ?


Indeed, does the use of such boundary conditions lead to a uniform flow in the whole domain because it is the mathematical solultion of the incompressible Navier-Stokes equations ? If so, how to model the development of an incompressible jet flow for instance ?


Thank you