# Boundary condition analysis for turbomachinery

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 November 1, 2013, 06:15 Boundary condition analysis for turbomachinery #1 Senior Member   sivakumar selvaraju Join Date: Mar 2009 Location: Cape Town - South Africa Posts: 186 Rep Power: 9 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

November 4, 2013, 04:46
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Antonio
Join Date: Jan 2013
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Quote:
 Originally Posted by sivakumar 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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