Fluids

Fluids

Floating point exception in cavitating flow over hydrofoil simulation

    • adarsh
      Subscriber

      Dear all, I am trying to simulate cavitating flow over a hydrofoil on FLUENT. For some reason, I seem to be getting a floating point exception error and the calculation stops. What can be the reason for this? 


      I believe I have a good mesh ( average skewness 0.008). The boundary conditions are as follows:


      Inlet ( Velocity inlet) velocity magnitude - 7 m/s and angle of attack 8 degrees.


      outlet ( pressure outlet) gauge pressure 0 pa.


      Also how can we set the cavitation number on fluent? 

    • Raef.Kobeissi
      Subscriber

      Hi, 


      Can you give more explanation about the cavitation number? Also please see this tutorial on cavitation:


    • adarsh
      Subscriber

      The Cavitation number (Ca) is a dimensionless number used in flow calculations. It expresses the relationship between the difference of a local absolute pressure from the vapor pressure and the kinetic energy per volume, and is used to characterize the potential of the flow to cavitate.


      It is defined as



      {displaystyle mathrm {Ca} ={frac {p-p_{mathrm {v} }}{{frac {1}{2}}rho v^{2}}}}


      where



      • rho  is the density of the fluid.

      • p is the local pressure.

      • p_{{mathrm  {v}}} is the vapor pressure of the fluid.

      • v is a characteristic velocity of the flow.


      So i set the cavitation using the pressure at pressure outlet. So for a range of 1.2 -2 I calculate the p in the above equation and then subtract the atmospheric from it. 


      I have already watched the tutorial and modelled my problem on this. I cant seem to generate any lift on the hydrofoil for some reason. and also the drag is very low compared to experimental cases

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