I'm working on an airfoil prof
I'm working on an airfoil profile NACA0012. I wrote my mesh in Gambit and then i imported it in OpenFOAM. I'm going to solver it with simpleFOAM (incompressible and steady flow, using kepsilon model) but the solution isn't accurate i think. At the angle of attack = 15° not stall and the total force on the profile is very low (i've calculated them using ssimpleFoam found in the board). I'd like to know:
1) what are the correct boundary condition on k and epsilon (in what way i give the correct k and epsilon fixed values on inlet patch and in internal field?) 2) do i have to use another model of turbulence? Thanks in advantage Emanuele |
I think, you must use freestre
I think, you must use freestream BC for infinity field, standard wall BC for walls on profile and inlet for inlet patch.
inlet: U - fixedValue, p - zeroGradient, k - fixedValue, epsilon - fixedValue infinity field - U - freestream, p - freestreamPressure, k and epsilon - zeroGradient. profile walls - U - fixedValue (0 0 0), p - zeroGradient, k and epsilon - zeroGradient |
what are the fixed values of k
what are the fixed values of k and epsilon to setting? is there a mode to calculate them?
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what kind of model of turbulen
what kind of model of turbulence is better??
and for the better what are the boundary condition on the k epsilon or another variable? what is the better schemes to use? |
For k/epsilon, I normally spec
For k/epsilon, I normally specify turb. intensity and the mixing length. I don't say that you have good values for these, but I find them a bit easier to visualize than the raw tke and dissipation.
The boundary conditions for 10% turbulence and 5mm length scale would look something like this: // k dimensions [ 0 2 -2 0 0 0 0 ]; internalField uniform 1; ... inlet { type turbulentIntensityKineticEnergyInlet; intensity 0.1; value 1; } // epsilon dimensions [ 0 2 -3 0 0 0 0 ]; internalField uniform 200; ... inlet { type turbulentMixingLengthDissipationRateInlet; mixingLength 0.005; value uniform 200; } NB: The stability of your calculation can be greatly affected by the initialization of epsilon. |
the value on inlet patch of k
the value on inlet patch of k and epsilon affect very greatly the solution...also using komega model you can choose the initial values very well....in what way can i fix this initial values (of k epsilon and omega) to obtain the correct solutions??
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Hello,
what does
"valu
Hello,
what does "value 1;" in k and "internalField uniform 200;" in epsilon stand for? It is the same as internalField, why do we need it in the BC-description? Regards Markus |
Hi at all,
i'd like to continue this thread because I have a lot of trouble with bounding k/epsilon although there are so many threads concerning this topic. so far I know that the initialization of k and epsilon is very important to achieve a stable calculation. but actually I don't really know what went wrong. I would like to simulate a flow throw a piston valve using the simpleFoam solver with the RNG k_epsilon model. Here are my settings. Maybe you can take a look what should be changed to get a stable calculation: p Code:
boundaryField Code:
boundaryField Code:
internalField uniform 0.0003; Code:
internalField uniform 1.35e-4; Code:
internalField uniform 0.1; Code:
application simpleFoam; Code:
ddtSchemes Code:
solvers Regards! |
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