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Floating Point Exception for rhoCentralFoam at Mach 7 |
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#1 |
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Join Date: Aug 2022
Location: Mexico
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I am simulating hypersonic flow in a variable geometry (I'm using the compressible forwardStep folder as a guideline). I'm able to run the simulation at Mach 4, but when increasing the velocity to Mach 5, 6 or 7 I get a floating point exception.
The mesh quality is good (I did the Mesh in Fluent and then exported it into OpenFoam) I aimed for the mesh to be as fine as possible with high orthogonality, low skewness and a high average quality. But I just can't figure out why am I getting this error, does rhoCentralFoam have a maximum Mach Number? Is there any other option to simulate Mach 6 or 7? Should I lower my deltaT (currently set at 0.002 with endTime at 4)? Here are my details: Knowing that from the thermophysicialProperties *Note: these are the properties for a "normalised" inviscid gas for which the speed of sound is 1 m/s at a temperature of 1K and gamma = 7/5 And the values for U, T and P are as follows: For U: Code:
internalField uniform (5 0 0); boundaryField { inlet { type fixedValue; value uniform (5 0 0); } outlet { type inletOutlet; inletValue uniform (5 0 0); value uniform (5 0 0); } bottom { type symmetryPlane; } top { type symmetryPlane; } obstacle { type slip; } defaultFaces { type empty; } } Code:
internalField uniform 1.197; boundaryField { inlet { type fixedValue; value uniform 1.197; } outlet { type zeroGradient; } bottom { type symmetryPlane; } top { type symmetryPlane; } obstacle { type zeroGradient; } defaultFaces { type empty; } } Code:
internalField uniform 0.22; boundaryField { inlet { type fixedValue; value uniform 0.22; } outlet { type inletOutlet; inletValue uniform 0.22; value uniform 0.22; } bottom { type symmetryPlane; } top { type symmetryPlane; } obstacle { type zeroGradient; } defaultFaces { type empty; } } Code:
application rhoCentralFoam; startFrom startTime; startTime 0; stopAt endTime; endTime 4; deltaT 0.002; writeControl adjustable; writeInterval 0.1; purgeWrite 10; writeFormat ascii; writePrecision 6; writeCompression off; timeFormat general; timePrecision 6; runTimeModifiable true; adjustTimeStep yes; maxCo 0.2; maxDeltaT 1; |
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#2 |
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Anyone that could point me in the right direction?
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#3 |
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Quick update:
I added viscosity in the thermophysicalProperties, and now the floating point error has gone and now it's a negative temperature issue, with led me to believe I'm dealing with a Meshing issue. After several meshing iterations, I was able to run my geometry when I used the 'original' boundary conditions of:
Any idea on how could I set the BC I'm trying to work with? |
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#4 |
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chandrashekhar a patankar
Join Date: Mar 2023
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try to use a different solver like "sonicFoam" and check, it might be more appropriate
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#5 | |
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Quote:
Thank you! Honestly I've been all over the place, and sonicFoam is not running for my geometry at Mach 7. I tried doing a more coarse mesh and, it's been running (some good and some bad results) but I'm still trying to figure out how to input my initial conditions with the thermophysicalProperties set by rhoCentralFoam: Any suggestion? Code:
thermoType { type hePsiThermo; mixture pureMixture; transport const; thermo hConst; equationOfState perfectGas; specie specie; energy sensibleInternalEnergy; } // Note: these are the properties for a "normalised" inviscid gas // for which the speed of sound is 1 m/s at a temperature of 1K // and gamma = 7/5 mixture { specie { molWeight 11640.3; } thermodynamics { Cp 2.5; Hf 0; } transport { mu 0; Pr 0.7; |
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#6 |
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Join Date: Nov 2017
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Maybe you need to set the ground energy of the solver by adding Tref and Href values in thermodynamics section.
You can also take a look to another thread about negative temperature issue: temperature negative occurred in rhoCentralFoam at high M |
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#7 | |
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Quote:
Thank you! Sorry for the late reply! I made it run beautifully by lowering deltaT by A LOT... which makes sense when working with a LES simulation, a very fine Mesh and high velocities. It's taking time to run though, but it's looking great! Thank you! |
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