[zhaowei]

Hi, all


I have done some simulation of aircraft propeller using MRFSimpleFoam, and the result goes well with ANSYS CFX. MRFSimpleFoam is used for incompressible steady state simulation. Now I want to change the flow density to see the performance of the propeller. It is very easy to change it in CFX, but how can I change the density of flow in OpenFoam?

I have read some theads said that OpenFoam use kinematic viscosity which is normalized by the density, and pressure is too. I have changed the reference pressure in fvSolution and mu in transportProperties, but the axial thrust does not change . Could anyone tell me how can I change the density? Thanks in advance.

[alberto]

You have to change the viscosity:

nu = mu/rho

being

mu -> dynamic viscosity
nu -> kinematic viscosity
rho -> density

Best,

[zhaowei]

Hi, Alberto

Thanks very much for your reply. I have changed the viscosity, but the axial force still not change. I use k-epsilon model, so should I change k and e?


thanks

[zhaowei]

Oh, I forgot to post my transportProperties file.

the original one is as follows:

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 1.5 |
| \\ / A nd | Web: http://www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object transportProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

transportModel Newtonian;

nu nu [0 2 -1 0 0 0 0] 1e-05;

CrossPowerLawCoeffs
{
nu0 nu0 [0 2 -1 0 0 0 0] 1e-06;
nuInf nuInf [0 2 -1 0 0 0 0] 1e-06;
m m [0 0 1 0 0 0 0] 1;
n n [0 0 0 0 0 0 0] 1;
}

BirdCarreauCoeffs
{
nu0 nu0 [0 2 -1 0 0 0 0] 1e-06;
nuInf nuInf [0 2 -1 0 0 0 0] 1e-06;
k k [0 0 1 0 0 0 0] 0;
n n [0 0 0 0 0 0 0] 1;
}

[zhaowei]

Oh, sincerely sorry everyone. I use the libturboPerformance.so to calculate the performance of rotor. I forgot to change the density there.

[hz283]

Originally Posted by alberto

You have to change the viscosity:

nu = mu/rho

being

mu -> dynamic viscosity
nu -> kinematic viscosity
rho -> density

Best,

>>>>>>>>>----------------------------------------------->>>>>>>
Now in my simulations, there are two streams: one is air and the other is pure methane. So in this case, how to set the nu? Is it still correct to give an approximate uniform value for the whole field? Thank you very much.

[hayhari]

Originally Posted by hz283

>>>>>>>>>----------------------------------------------->>>>>>>
Now in my simulations, there are two streams: one is air and the other is pure methane. So in this case, how to set the nu? Is it still correct to give an approximate uniform value for the whole field? Thank you very much.

Hi

I am new to openFoam. Did you get the answer for your question.?? please tell me how can we tackle this issue..

[cramsdead]

Hello hayhari,

I have just a simple question :
Is it possible to set a "density" into a block to let more or less the fluid going throught?
I mean, they is only the permeability to set it or there is other Options?

Thanks for your reply

[EddySouth]

Originally Posted by zhaowei

Hi, all


I have done some simulation of aircraft propeller using MRFSimpleFoam, and the result goes well with ANSYS CFX. MRFSimpleFoam is used for incompressible steady state simulation. Now I want to change the flow density to see the performance of the propeller. It is very easy to change it in CFX, but how can I change the density of flow in OpenFoam?

I have read some theads said that OpenFoam use kinematic viscosity which is normalized by the density, and pressure is too. I have changed the reference pressure in fvSolution and mu in transportProperties, but the axial thrust does not change . Could anyone tell me how can I change the density? Thanks in advance.

For incompressible flow, the density is constant and set as 1 in openfoam. But I don't know how to deal with compressible one.