Simple algorithm problem
 

Hi everyone!
I am solving the flow inside an elbow using the finite volume method, coded by the simple algorithm. In this case, when the knee angle reaches 90 degrees, the problem diverges, but there is no particular problem at angles less than 90 degrees. What do you think could be the reason for this problem? I checked many items in the code but unfortunately I could not find the problem
Below is an example of a convergent flow for angles less than 90. Currently, the flow is considered to laminar and with low Reynolds number.


https://www.cfd-online.com/Forums/at...1&d=1623007281