Residuals problem
 

Hi foamers,

I have been trying to model flow through a Nozzle, the geometry of which can be seen in the attached picture. I have a flowRateInletVelocity BC at my inlet, where the flowRate is being ramped from 0.001 to 0.00397 in 0.001 increments every 100 time steps. The pressure blows up when I run the simulation and gives some strange residuals. I have not encountered residuals like these before (see 2nd attached picture).

Does anyone have any ideas that will help me maintain a steady residual for my pressure? Thank you in advance for any help that anyone can offer.

Kind Regards,
Tom

You don't specify the solver you use in this case but I guessed it is a single phase flow solver (pisoFOAM) with turbulence model. From what I saw in the residuals, I think it is not converged due to the lack of PISO loop. I think if you try to increase the number of correctors in fvSolution until the initial residual of p decreases to 10^-5 or so and use momentum predictor if required, that problem might disappear.

And if it is the convergence problems of the solver (looking at the final residual of p in the log file), you might want to use another solver, smoother etc.

Hope it can help.

Duong

Hi Duong,

Thanks for your reply, I am using rhoSimpleBaffleFoam a modified version of the rhoSimpleFoam solver, I must use this solver so I can't change it. However I will look into your suggestions nonetheless.

Thanks
Tom