Robert Woolhouse
Ansys Employee
Yes, patch. Otherwise the solver needs to pressurise the upstream section but also wants to have a shockwave there as the high pressure gas enters the domain. It'll eventually get to a stable solution but it may take a while.
Re-read the section on the wall functions. y+ = 1 means you're likely to be resolving the near wall gradients; y+ 30-300 or so means you're using a model which may have limitations.