Peter Rozovski
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June 11, 2001 23:47 |
Re: unidimentional nozzle
Probably it is code bug (I have not looked at your program - no comments and variable names in German :)) but more similar that you have met problem with calculation stability problem in critical section of Laval nozzle. As it is described in many textbooks (Pirumov-Roslyakov, Sternin,...) the steady subsonic-supersonic quasi-one-dimensional Euler system of equations can be rewritten as one equation for M and at critical cross-section in case of frozen flow (or after critical cross-section in case of non-equilibrium flow) it is special point with term DF/dx /(M**2-1). Some solvers (like LSODE) allow to pass this point smoothly, othes - not. One of possible methods to avoid this problem - to use "inverse" method - when you set not F(x), but ro(x), which can be calculated from isoentrophic relations (even in case of non-equilibrium flows density distribution is very close to frozen distribution). In this case this special point dissapear.
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