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-   -   Thermal, Buoyant, Gas-Mixing, Stead-State Turbulent Solver (http://www.cfd-online.com/Forums/openfoam-solving/102934-thermal-buoyant-gas-mixing-stead-state-turbulent-solver.html)

iamed18 June 6, 2012 12:04

Thermal, Buoyant, Gas-Mixing, Stead-State Turbulent Solver
 
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Good Morning Everyone!

I've got what seems like a daunting task ahead of me. My project requires me to use a solver that can do a simulation of a hot exhaust plume (we'll call it type 1) being spewed into the atmosphere (call it type 0), taking into account that these are two different species with two different thermal expansion/diffusion coefficients mixing with Reynolds numbers on the order of millions.

Let me explain my thoughts so far (I'm new to CFD and have only been trying to grasp OpenFOAM for the past 3-4 weeks, so please point out my naiveties as I'm sure they are many). I should also note that I'm not only new to CFD, but to fluid dynamics in general. I've spent many hours pouring over material over the past month, as well as playing with the example simulations in OpenFOAM to try to get a grasp on some of the more basic phenomena in the field.

Baby Steps First
As it appears that OpenFOAM is the kind of package in which you must suck your thumb before you can sit up before you can crawl before you can walk before you can run, I've spent some time using different solvers on my mesh. I've been met with both successes and failures, but I remain optimistic (and really quite impressed) based on what I've seen so far.

My current state of successful progress has me using a modified version of simpleFoam, in which I followed this guide to add a scalar transport model for temperature. This seems to be working, and I've attached the corresponding 0 directory.

What currently troubles me: When I use the exact same conditions and geometry under buoyantBoussinesqSimpleFoam, since it has most of my requirements built-in (thermal, buoyancy, steady-state turbulence), the simulation yields remarkably non-physical results (I get speeds on the order of Mach 45).

So my question to everyone is: what should I try next? I have a feeling that the Boussinesq approximation might not be the best method of attack for my buoyancy issues (mainly because my temperature differences are on the order of 100 K). I also don't know if I should be trying to accomplish buoyancy or gas mixing first (or if the two should be tackled simultaneously).

Thanks for reading, and I look forward to reading your responses!
~Ed


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