|April 24, 2012, 10:29||
heat transfer with RANS wall function, over a flat plate (validation with fluent)
Join Date: May 2009
Posts: 38Rep Power: 6
I am following this test case,(forced convection over a flat plate)
OpenFOAM vs (Fluent & Theory & Experiment)
It is a compressible, RANS, low-Re grid with realizable k-epsilon model. The above link matches that fluent , theory , experiment results in agreement.
My aim is to prove the same from OpenFOAM side.
I use 2.1.x (latest git) rhoSimpleFOAM solver, realizableKE (RANS turbulence model !)
So i try to use same settings as in fluent above.
Test 1: laminar
The heat transfer values at the plate are in agreement with fluent. I have used (wallHeatFlux -latestTime) the standard utility
Test 2: with turbulence model
The heat transfer values are quite different !! My doubt is either the realizableKE model or wall functions.
Since the pressure variations are very small, it is not a good idea to work with abs. pressure field , so i modified thermophysical models and recompiled rhoSimpleFoam solver. Now that, i have guage pressure formulation for pressure !!!
Now i do not know why i get different wall heat flux value on the plate when compare to fluent (of course, fluent results are in agreement with experiment and theory as i said above)
inside rhoSimpleFoam: run ./Allwmake
if you need laminar test case , let me know.
The heat flux value from fluent and OpenFOAM (in case you do not have fluent)
#position Fluent OpenFOAM 0.0166667 322.544 284.76711 0.05 220.942 85.636212 0.0833333 200.35 62.086357 0.116667 188.401 52.34236 0.15 179.175 46.641522 0.183333 171.331 42.556804 0.216667 164.508 39.520929 0.25 158.538 37.0035 0.283333 153.292 35.036207 0.316667 148.668 33.252812 0.35 144.577 31.856434 0.383333 140.945 30.491744 0.416667 137.708 29.45537 0.45 134.812 28.357696 0.483333 132.213 27.569636 0.516667 129.872 26.652224 0.55 127.754 26.048582 0.583333 125.833 25.257404 0.616667 124.084 24.79662 0.65 122.486 24.094795 0.683333 121.021 23.750895 0.716667 119.673 23.112447 0.75 118.428 22.866211 0.783333 117.276 22.272958 0.816667 116.202 22.109839 0.85 115.206 21.549314 0.883333 114.267 21.455807 0.916667 113.377 20.919178 0.95 112.623 20.88645 0.983333 111.442 20.361769
If someone is curious to validate OpenFOAM Wall function here, Link for OpenFOAM test case,
|May 2, 2012, 04:56||
DAOU Mehdi Pierre
Join Date: Apr 2012
Posts: 1Rep Power: 0
I observe the same differences for the heat flux value between fluent and OpenFOAM for this test case.
I use buoyantSimpleFoam solver, realizableKE.
I don't understand these differences.
If someone has an idea of the reason for these differences?
I think if the can come from the difference of calculated heat flow.
I calculate the heat flux: k * magGradT and magGradT is calculated with "foamCalc magGrad T"
And I compare in Fluent with Total Surface Heat Flux but I don't sure that it is equivalent.
Last edited by DAOU M.P.; May 2, 2012 at 10:57.
|May 4, 2012, 14:44||
Join Date: May 2009
Posts: 38Rep Power: 6
In order to simplify my case, i created blockMesh coarse grid with yPlus (or yStar) from 16 to 23. And have changed turbulence model to standard k-epsilon instead of realizableKE.
I have results from fluent with standard k-epsilon with standard wall function so that i would verify this in OpenFOAM. Unfortunately, it is still not comparable. I feel that there could be a bug some where.
I used rhoSimpleFoam although buoyancy solver can also be used, it is the same for our case.
Heat flux in OpenFOAM is: qDot = alphaEff| v-> f * grad(h) but i am not sure about fluent.
here is the complete case set:
Upon generating results which is comparable to fluent, one can say that OpenFOAM wall functions are working as so.
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