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-   -   Boundary condition analysis for turbomachinery (http://www.cfd-online.com/Forums/openfoam-pre-processing/125835-boundary-condition-analysis-turbomachinery.html)

sivakumar November 1, 2013 06:15

Boundary condition analysis for turbomachinery
 
Hi there,
I am working on axial flow fan, its an annular case.
I am using OpenFOAM for my simulation.
I have give the BC, as discribed in the user manual
inlet - massflow or velocity (fixed value)
outlet - fixedValue (0), I know its not wrong, however we are forcing the pressure to zero at outlet face, so I want to say its not an appropriate one.

Then, I have given a try to fixedMeanValue (0) at outlet for pressure, it seems the result which I obtained from this BC is reasonably fine. however I want to check the deviation from the radial equilibrium solution. I am bit confused here to get the analytical solution for radial equilibrium condition. dp/dr = rho *v^2/r
v --> swirl velocity
r --> radius


my question is:

how can I get the swirl velocity?

can you people give a hit to solve the problem?

Thanks,
Sivakumar

avigrod November 4, 2013 04:46

Quote:

Originally Posted by sivakumar (Post 460129)
Hi there,
I am working on axial flow fan, its an annular case.
I am using OpenFOAM for my simulation.
I have give the BC, as discribed in the user manual
inlet - massflow or velocity (fixed value)
outlet - fixedValue (0), I know its not wrong, however we are forcing the pressure to zero at outlet face, so I want to say its not an appropriate one.

Then, I have given a try to fixedMeanValue (0) at outlet for pressure, it seems the result which I obtained from this BC is reasonably fine. however I want to check the deviation from the radial equilibrium solution. I am bit confused here to get the analytical solution for radial equilibrium condition. dp/dr = rho *v^2/r
v --> swirl velocity
r --> radius


my question is:

how can I get the swirl velocity?

can you people give a hit to solve the problem?

Thanks,
Sivakumar

I guess there are better and easier options in paraFoam for getting Vu, but I would try in this two ways:
1) Getting Vx, Vy and Vz in the disk rotor by using a sampleDict* (and also angular position/velocity of the rotor if not steady), and calculating Vr, Vu and Vx by hand in Octave/Matlab/Python whatever...
2) Writing a function Object for defining a coordinate transform tensor which moves Cartesian coordinates to cylindrical within the rotor disk.


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