FreeSurface simulation

Chengxuan Fu

Hi,guys

i am doing an CFD analysis of a highspeed waterjet. water is pushed through a very narrow slit into a mixing chamber, where it is mixed with air ,which is accelerated by the water, and sand will be sucked into that chamber. In the end, the mixture injects out of a focusing tube with speed up to 300 to 400 m/s, and metal like Al could be cut by such a machine.

To obtain the necessary speed of water, the slit has to be very narrow, around 10um, and we need very high Psta, 200Mpa to 400Mpa.

i am doing a freesurface simulation , to see how water is interacting with air in the chamber and focusing tube.and i want to optimize the geometry of the design with the results from CFD.

But the problem now, is the calculation is very slow and i need hundreds of PISO corrector stages .

my questions are

1.how to speed up the calculation , yet let it still converge

2.is there any way to disable .info file, because i tried to use AMG method, then the info file became extremely large

3.what is the advantage of AMG method

4.my Re number ranges from 1500 to 15000 in the whole model , which is not completely full with one phase, what kind of turbulent model should i choose

5.in which cases should i turn on subcycling

thanks chengxuan fu