Residuals k shooting up

Stels · April 20, 2017, 11:30

Hello people,
I am doing currently a combustionsimulation of a rocketchamber(from Injektion- Inlet til Nozzlethrout) under superkritical conditions.(non-premixed PDF, SST, real gas). As my solution converges suddently the residuals of K shoot up and the simulation crushes.What could be the reason for that? Will be very thankfull for help.Picture in attachment)

LuckyTran · April 20, 2017, 17:55

It's likely the result of a poor initial guess. Either take a better guess or baby the software a bit and steer it towards a better solution.

The most common thing I see is that people guess a uniform pressure, velocity, and temperature field for a high speed flow and pray that the simulation converges, but then it blows up. One thing that helps is to freeze the energy equation for the first 100 iterations or so and let the pressure catch up and then enable it.

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April 20, 2017, 17:55		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,751 Rep Power: 66	It's likely the result of a poor initial guess. Either take a better guess or baby the software a bit and steer it towards a better solution. The most common thing I see is that people guess a uniform pressure, velocity, and temperature field for a high speed flow and pray that the simulation converges, but then it blows up. One thing that helps is to freeze the energy equation for the first 100 iterations or so and let the pressure catch up and then enable it.