# Convergence Problem Supersonic Flow Laval Nozzle

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 December 5, 2005, 10:55 Convergence Problem Supersonic Flow Laval Nozzle #1 Tobias Guest   Posts: n/a Hello I simulate a Laval Nozzle. The nozzle is part of a real wind channel and the part which creates supersonic flow at the outlet (Ma >2.0). I use subsonic pressure inlet (total pressure, total temperature) and supersonic outlet. Two Problems occur, maybe somebody got some advices (solution strategies) for me: First, overall massflow is too small (no shock occurs!!) If I choose massflow inlet, solution crashs because of to big mach number. Thanks to you, Tobias.

 December 6, 2005, 06:21 Re: Convergence Problem Supersonic Flow Laval Nozz #2 Bart Prast Guest   Posts: n/a 1. Use the expert parameter: max continuity loops = 2 (you should always do this for supersonic flows) 2. Do not start up with a supersonic outlet as it will not be a supersonic outlet when you start the calculation. Start first with a pressure boundary untill you have supersonic conditions at the outlet (then switch over)

 December 6, 2005, 06:24 Re: Convergence Problem Supersonic Flow Laval Nozz #3 Bart Prast Guest   Posts: n/a I forgot: How can you use a supersonic outlet condition when you expect a shock????? The flow will be subsonic after the shock and at the exit of your nozzle.

 December 7, 2005, 01:23 Re: Convergence Problem Supersonic Flow Laval Nozz #4 tobias Guest   Posts: n/a Thanks for your advices Bart, I'll try them. I studied the modelling guide and suggest now the same way how to solve this porblem. By definition of a supersonic outlet I supposed CFX to find the solution without the present of a shock, but I failed. If it works, I'll report. Thaks to you, tobias.