Learning Forum

[2019023289]

Hello,

I'm studying jet impingement now. For Pressure-Velocity coupling algorithm，if I choose coupled algorithm,there is large backflow. If  I choose SIMPLE  algorithm ,there is no backflow at first.However, as the calculation goes on, there is backflow at last, but it is smaller than Couple algorithm.

So is it caused by algorithm, or is it a normal physics phenomenon？

Thanks

[Rob]

Jets tend to entrain flow, and depending on the boundary conditions that may come from the outlet: hence backflow.  I'd expect a similar result from SIMPLE and PBCS if run to full convergence, so suspect the difference will reduce with iterations. 

[2019023289]

Thank you,sir!

In fact, there was a small backflow at the beginning of the calculation, but the backflow disappeared with the calculation, and finally there was a large backflow again, and the residual curve fluctuated.

[Rob]

Have a look at the velocity field. CFD convergence isn't solely judged on the residuals, you need to check the flow field and monitors. I also suggest reading up on the back flow direction options. 

[DrAmine]

Can you share a picture of the geometry where we can identify the outlets?