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Error when modelling hypersonic flow over a cone

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Hi all,

I'm attempting to model reentry speed flow (approx mach 25) over a cone in 2-D axi. It's a stationary model using the high mach number flow, Spalart-Allmaras physics.

The issue I'm having is that when I try to compute i get this error:

Failed to find a solution.
Segregated Step 1
Attempt to evaluate nonintegral power of negative number.
Function: ^
Failed to evaluate variable.
Variable: comp1.hmnf.mu, Defined as: ((comp1.hmnf.mu ref*((comp1.T/comp1.hmnf.Tmu ref)^1.5))*(comp1.hmnf.Tmu ref+comp1.hmnf.S s))/(comp1.T+comp1.hmnf.S s)
Failed to evaluate variable.
Variable: comp1.hmnf.mu eff, Defined as: comp1.hmnf.mu+comp1.hmnf.muT
Failed to evaluate temporary symbolic derivative variable.
Variable: comp1.hmnf.K stress tensor testrzVDN${test3}, Defined as: comp1.hmnf.mu eff
Failed to evaluate expression.
Expression: d(comp1.hmnf.K stress tensor testrz,{test3})
Failed to evaluate Jacobian of expression.
Expression: comp1.hmnf.K stress tensor testrz
Failed to evaluate Jacobian of operator.
Operator: mean, Geometry: geom1, Boundary: 5
Failed to evaluate Jacobian of variable.
Variable: comp1.hmnf.K stress tensor testrz, Geometry: geom1, Boundary: 5
Failed to evaluate Jacobian of expression.
Expression: (2*(comp1.hmnf.KStressn avr*test(comp1.hmnf.u herer)+comp1.hmnf.KStressn avz*test(comp1.hmnf.u herez)+comp1.hmnf.KStressTestn avr*comp1.hmnf.ujumpr+comp1.hmnf.KStressTestn avz*comp1.hmnf.ujumpz-comp1.hmnf.sigma dg ns*comp1.hmnf.unJump*test(comp1.hmnf.un here)+comp1.hmnf.upwind ns+comp1.hmnf.upwindCont+comp1.hmnf.consFlux)*pi*r)*(dvol)
In Turbulence variables:
Returned solution is not converged.

The problem seems to be with this equation: (comp1.T/comp1.hmnf.Tmu ref)^1.5
I'm confused as to how either of these could be negative, as they are both temperatures given in Kelvin.

Any help would be much appreciated

2 Replies Last Post Nov 25, 2016, 11:34 a.m. EST

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Posted: 8 years ago Nov 25, 2016, 10:58 a.m. EST
Hi,

well... I am not an expert in COMSOL nor in the physics that you want to simulate.
But, I am not sure if you can use "^1.5" in COMSOL. Try to use "e1.5" instead...
Let me know if this was the problem!

Cheers!

--
Mateus
______________________________________
PhD at Université de Genève & CERN
Genève, Switzerland
Hi, well... I am not an expert in COMSOL nor in the physics that you want to simulate. But, I am not sure if you can use "^1.5" in COMSOL. Try to use "e1.5" instead... Let me know if this was the problem! Cheers! -- Mateus ______________________________________ PhD at Université de Genève & CERN Genève, Switzerland

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Posted: 8 years ago Nov 25, 2016, 11:34 a.m. EST
Thanks for your answer Mateus.

The equation that's in question is built into COMSOL, it's part of Sutherland's Law for calculating the dynamic viscosity of the flow. It's not something I can edit so the problem seems to be with the values handed to it. Somehow one of the temperature values is negative Kelvin, which is... interesting.

Thanks,

Ben

Thanks for your answer Mateus. The equation that's in question is built into COMSOL, it's part of Sutherland's Law for calculating the dynamic viscosity of the flow. It's not something I can edit so the problem seems to be with the values handed to it. Somehow one of the temperature values is negative Kelvin, which is... interesting. Thanks, Ben

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