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Species Transport Convergence trouble in Supersonic Flow

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Old   February 28, 2017, 12:18
Default Species Transport Convergence trouble in Supersonic Flow
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Brian B.
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Hello-

I am a very new user to ANSYS Fluent and was assigned it to complete a Master's distance learning project for a class that I am currently taking.

I am analyzing skin friction and surface heating in a 2D supersonic flow with different fuels being injected into the BL. The flow properties are Mach 5 at the inlet, with a gauge static pressure of 83000 Pa. I am using a Chemkin mechanism for H2 oxidation, with 10 species and 21 reactions. I have success when I do not initiate the reaction mechanism, i.e. a cold flow, and am able to get a converged solution in this case. When I initiate the reaction, the residuals for continuity, x-velocity, and y-velocity jump to around 1e-01, and the residuals for the species jump 10 orders of magnitude, with some being around 1e+09. I know this isn't right.

I've checked my mesh, it's got around 300000 nodes and is finer around the fuel-inlet and boundary layer. I can't do much more refinement to the mesh as it's the student version of ANSYS and I am limited to around 500000 nodes.

As far as the solver goes, I using a density based solver with reduced under-relaxation factors. I'm using the standard k-e viscous model as well as enabling the stiff chemistry solver for the species transport. I've treied changing the viscous model to start with S-A or even laminar flow to no avail.

Any help or ideas would be appreciated. Thanks.
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combustion, scramjet, species, supersonic, transport

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