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Old   December 29, 2010, 00:21
Unhappy De Laval nozzle
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Fayaaz Hussain
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Hey Guys I'm currently trying to simulate flow through a de laval nozzle to show under expansion, over expansion and barrel shocks etc. I used GAMBIT for meshing..I am totally new to CFD as I'm currently a undergrad student so forgive my ignorance. I'm able to get the desired results for a mesh with interval size 0.5 with inviscid and laminar flows that too with third order discretization. Results diverge for second order discretization. When I try for a mesh with 0.1 interval the results diverge for all orders of discretization.

Can anyone please help??
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Old   December 29, 2010, 02:27
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Alexey
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Quote:
Originally Posted by fayaazhussain View Post
I'm able to get the desired results for a mesh with interval size 0.5 ... When I try for a mesh with 0.1 interval the results diverge for all orders of discretization.
It seems your numerical algorithm is bad...
But may be the reason is other. If you use explicit time scheme then you should keep stability Courant condition
\Delta t < \frac{\Delta x}{|u|+c}

So when you have reduced dx (keeping dt=const) this condition could be broken.
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