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-   -   turbulent jet simulation (http://www.cfd-online.com/Forums/openfoam-solving/69300-turbulent-jet-simulation.html)

antonio_ing October 19, 2009 07:27

turbulent jet simulation
 
hi Foamers.

I'm trying to simulate the coaxial jet flow field for my PhD thesis. I tried to create the mesh and set up the case but there is some floating point error, maybe due to wrong boundary conditions. Does someone have some simulation of an axisymmetric round jet or even suggest me the boundary conditions?

thanks in advance

heavy_user April 1, 2010 11:58

Hi Antonio,

did you get any further with your problems?
I am having a similar issue right now..

regards!

natrask April 1, 2010 13:45

Hi Antonio,

I'm actually just finishing my thesis work writing a solver to predict turbulent atomization of a similar type of injector (gas-centered swirl coaxial). You can find a paper describing our work here (http://oai.dtic.mil/oai/oai?verb=get...fier=ADA513613). We did a number of validation cases, one of which was a coaxial fuel injector, and another being a diesel plain orifice injection.

The problem with predicting these guys in OpenFOAM is that the only appropriate solver that's released is interFoam (or one of the other interface tracking variations) which require mesh resolution of the scale of the droplet size (which is prohibitively small for the Weber numbers we're usually looking at). You could try a Lagrangian method (like the one that's set up in dieselFoam) but that won't account for the volume occupied by the liquid phase. For coax injectors, the liquid core profile can significantly alter the recirculation zone that forms between the two phases.

I'd be happy to share my code once I get it polished up (maybe by the end of April?).

heavy_user April 6, 2010 04:57

Hi natrask,

nice work! Your results seem to be pretty close to the "real world" !

Would you mind posting a setup of your case?
With BC and stuff?

regards!

JMP May 10, 2010 08:07

Hi Nat,

Your approach and results seems quite interesting. We've got some experience with lagrangain methods, both on StarCD and OpenFOAM, but your approach could solve some issues when applying to dense sprays. Indeed I'm quite interested on coding this type (sigma-Y or 'ELSA') spray models into OpenFOAM. If you could share some details about your implementation or any additional publication it would be quite helpful.
Thanks

Regards

Jose

msarkar September 16, 2010 02:31

2 Attachment(s)
Hi All,

I am trying to simulate a heated air jet dispersion in an open area. The heated air is coming out from a pipe leak ( leak diameter 1cm) with a velocity of 135 m/s and a temperature of 100 C. In this case, the Mach-number is around 0.4 which is mildly compressible flow. So, I was using rhoSimpleFoam and rhoPImpleFoam. I tried several boundary conditions and mesh sizes but with out any success. The results do not look reasonable. As initial case I am considering a 2D rectangular geometry. Could you please suggest me which solver I should use?

The mesh and boundary file and one set of used boundary conditions are attached here. If you have any suggestions regarding boundary conditions, Please let me know. Any help would be very much appreciated.

top:
alphat: type calculated

epsilon:
type inletOutlet;
inletValue uniform 0.01;
value uniform 0.01;
k:
{
type inletOutlet;
inletValue uniform 0.1;
value uniform 0.1;
}

mut:
type calculated;

p:
{
type fixedValue;
value uniform 100000;
}

T:
{
type zeroGradient;
value uniform 333;
}

U:
{
type pressureNormalInletOutletVelocity;
//type slip;
phi phi;
rho rho;
value uniform (0 0 0);
}

bottom:
alphat: type calculated

epsilon:
type inletOutlet;
inletValue uniform 0.01;
value uniform 0.01;

k:
{
type inletOutlet;
inletValue uniform 0.1;
value uniform 0.1;
}

mut:
type calculated;

p:
{
type fixedValue;
value uniform 100000;
}

T:
{
type zeroGradient;
value uniform 333;
}

U:
{
type pressureNormalInletOutletVelocity;
//type slip;
phi phi;
rho rho;
value uniform (0 0 0);
}


inlet:
alphat: type calculated

epsilon:
{
type compressible::turbulentMixingLengthDissipationRate Inlet;
mixingLength 0.0005; // 0.01*0.05
value uniform 0.01;
}

k:
{
type turbulentIntensityKineticEnergyInlet;
intensity 0.05;
value uniform 0.1;
}

mut:
type calculated;

p:
{
type zeroGradient;
value uniform 100000;
}

T:
{
type fixedValue;
value uniform 373;
}

U:
{
type fixedValue;
value uniform (135.74 0 0);
}


outlet:
alphat: type calculated

epsilon:
{
type inletOutlet;
inletValue uniform 0.01;
value uniform 0.01;
}

k:
{
type inletOutlet;
inletValue uniform 0.1;
value uniform 0.1;
}

mut:
type calculated;

p:
{
type fixedValue;
value uniform 100000;
}

T:
{
type zeroGradient;
value uniform 333;
}

U:
{
type inletOutlet;
phi phi;
rho rho;
value uniform ( 0 0 0 );
inletValue uniform ( 0 0 0 );
}

lowerleft:
alphat:
type alphatWallFunction;
Prt 0.85;
value uniform 0;

epsilon:
{
type compressible::epsilonWallFunction;
Cmu 0.09;
kappa 0.41;
E 9.8;
value uniform 0.01;
}

k:
{
type compressible::kqRWallFunction;
value uniform 0.1;
}

mut:
{
type mutWallFunction;
Cmu 0.09;
kappa 0.41;
E 9.8;
value uniform 0;
}

p:
{
type fixedValue;
value uniform 100000;
}

T:
{
type zeroGradient;
value uniform 333;
}

U:
{
type fixedValue;
value uniform (0 0 0);
}


upperleft:
alphat:
type alphatWallFunction;
Prt 0.85;
value uniform 0;

epsilon:
{
type compressible::epsilonWallFunction;
Cmu 0.09;
kappa 0.41;
E 9.8;
value uniform 0.01;
}

k:
{
type compressible::kqRWallFunction;
value uniform 0.1;
}

mut:
{
type mutWallFunction;
Cmu 0.09;
kappa 0.41;
E 9.8;
value uniform 0;
}

p:
{
type fixedValue;
value uniform 100000;
}

T:
{
type zeroGradient;
value uniform 333;
}

U:
{
type fixedValue;
value uniform (0 0 0);
}


frontAndBack:

For all variables it is empty.


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