Hello, to update on this: it was the mesh. Not the quality but the AMI. There are a ton of AMI in pumps, I had 7 there. The one between the inducer and the impeller did weird stuff and I can only assume it was the reason of my inlet problems. I have a worse mesh now, maxNonOrtho 72, but I meshed inducer and impeller as 1, no more interface. Runs perfectly, simpleFoam went down to 2e-4 residuals everywhere fast