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2D Savonius Rotor simulation Validation problems

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    • Valeriy Willetts
      Subscriber

      Hello,
      I've been trying to simulate a 2D Savonius rotor and validate the power coefficient data with the laboratory data obtained in the paper I found, however, the ansys simulation underpredicts the experimental data. I constructed the geometry in spaceclaim, using dimensions given in the paper and carried out a mesh refinement study by measuring the torque when the rotor is stationary.

      As well as this, I tried to make sure that the y+ values at the walls of the rotor blades were <1.

      Using the sliding mesh approach I would change the rotational speed of the rotor and measure the torque to obtain the Torque coefficient and finally the Power coefficient to construct a power curve.

      The following input was used in set-up:
      1. Turbulence model: Transition SST (4 eqn)
      2. Fluid used: Air (1.225 kg/m3)
      3. Velocity inlet: x-component = 7m/s, y-component = 0 m/s
      4. Solution method used: SIMPLE with spatial discretization gradient set to least Square cells based, and all other parameters set to second order.
      5. Reference values are computed from the inlet.
      6. Torque was measured from both blades at the centre of rotation of the rotating domain.
      7. Hybrid initialization was used.
      8. The time step size was found using the CFL criterion ∆t≤ ∆x/v, where the number of time steps was adjusted at different rotor speeds whilst keeping the time step size constant.



      My Ansys data is extremely underpredicting the experimental data. Could anyone please give me some advice as to what might be going wrong? Thank you.

    • Federico
      Ansys Employee

      Are you using absolute Force or Moment values from Fluent? Or are you using coefficients? The latter will depend on the Area and Length reference values you set for your simulation.

    • Valeriy Willetts
      Subscriber

      Im using moment values from fluent

    • Federico
      Ansys Employee

      Other than CP, do you have any other data to compare with the paper?

    • Federico
      Ansys Employee

      Another thing to consider is whether the Torque you are getting accounts for the prescribed motion that you are setting.

      Perhaps you should consider using the 6DOF model 13.6. Using Dynamic Meshes (ansys.com) to get the true torque from the fluid acting on the rotor.

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