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Getting divergence while increasing the back pressure at pressure outlet

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Old   March 18, 2018, 23:39
Default Getting divergence while increasing the back pressure at pressure outlet
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Hi,

I'm trying to simulate 2D- planar over expanded jet in Fluent by enforcing the nozzle exit conditions at the inlet. i.e. setting Total Pressure, static pressure for a particular Mach no and total temperature at pressure inlet and changing the back pressure at pressure outlet. (Not using the c-d nozzle geometry)

I could obtain the perfectly expanded flow correctly, but when i tried to use that solution/data and increase the back pressure, I'm getting divergence..
---------------------------------------------------------------------------------
Divergence detected in AMG solver: temperature
Error at host: floating point exception

turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 10901 cells

Error at Node 0: floating point exception

Error at Node 1: floating point exception

Error at Node 2: floating point exception

Error at Node 3: floating point exception

Error at Node 4: floating point exception

Error at Node 5: floating point exception

Error: floating point exception
Error Object: #f

------------------------------------------------------------------
Parameters for M=3.17 at inlet
Operating Pressure = 0 Pa

1. Perfectly expanded jet:
Pressure inlet
Gauge Total Pressure:5000000 Pa
Initial Gauge pressure: 104965 Pa
Total Temperature: 300K

All Pressure outlets
Gauge pressure: 104965
Back flow Total Temperature: 300K


2. Over expanded jet
Pressure inlet
Total Pressure:5000000 Pa
Static pressure: 104965 Pa
Total Temperature: 300K

All Pressure outlets:
Gauge pressure: 390000 Pa
Back flow Total Temperature: 300K


Could you please give some suggestions to overcome this issue? My requirement is to increase the back pressure to reach 3rd critical condition, then reduce the back pressure to reach back to perfectly expanded state.

Thank you.
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