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Convergence issue of high speed flow simulation

Hi all,

 

I'm doing now a simulation of high speed flow of air thourgh out a pipe (~1 inch). At the inlet boundary, i put at mass flow at very high temperature, and at the other pipe exemit, its the ambiant outlet (atmospheric pressure). There is no thermal exchange between inner air and ambient environment. To solve this kind of fluidic simulation, i need the advanced flow solution.

 

In steady state, for a "small" mass flow, kind of 200g/s at 1200°C (for exp.), there is no prob. The simulation works well but when i put 600g/s and at same temperature, a "Linear solver divergence detected" error is shown. The timestep is reduced step after step but the program do not converge.

 

Does anyone have the same issue ?

 

BR,

 

2 REPLIES
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Solution
Accepted by topic author ngda
3 weeks ago

Re: Convergence issue of high speed flow simulation

Try incrementing the mass flow according to time.

 

So for example, if you have 10 time steps specified of 1 second each, make the mass flow 60*time/1[sec] g/s. At 10 seconds, you'll have 600 g/s.

 

Juan

Re: Convergence issue of high speed flow simulation

Hi Juan,

 

Your solution works perfectly in my case.

 

Many thanks !!

 

ngda