7 Replies Latest reply on Oct 23, 2015 9:02 AM by David Flemming

    Problem with flow simulation on a vertical axial  turbine (3 blade Giromill)

    Ijihj Ijijijij

      Hi,

      I am doing my bachelor thesis where i  design  a turbine using solidoworks in the flow simulation part i need  to make a curve perfomance,  Power coefficient versus T.S.R ,defining  a constant flow speed of 2m/s and variant rotational  rotor speed  but the outlet torque only increase then it´s imposible to make the curve

       

      Captura de pantalla 2015-10-13 19.45.48.pngCaptura de pantalla 2015-10-13 19.48.35.png

      the simulation is an internal flow rate through a tube.

      what´s wrong?

       

      Thanks in advance.

        • Re: Problem with flow simulation on a vertical axial  turbine (3 blade Giromill)
          David Flemming

          Hi...Considering your study is an internal analysis, I see you have defined the inlet boundary condition as a velocity (Inlet Velocity 1), but have you defined the outlet boundary condition? for example, an ambient static pressure.

          • Re: Problem with flow simulation on a vertical axial  turbine (3 blade Giromill)
            Amit Katz

            Your local rotating region is quite a bit larger than your turbine. Remember that every fluid cell inside of that region will be locked into the angular velocity that you set, so your model is likely not approximating reality very well.

             

            Additionally, remember that there is no fluid-structure interaction being simulated in Flow Sim. Any motion of the turbine is set ahead of time by the local rotating region definition. In that sense you are not really simulating a turbine here, it's more like simulating a fan or a mixer.

              • Re: Problem with flow simulation on a vertical axial  turbine (3 blade Giromill)
                David Flemming

                @Amit - you said that there is no fluid-structure interaction being simulated in Flow Sim. I'm relatively new to SW Flow Sim so I may be wrong, but I believe that there should be some interaction between the fluid and solids for a rotating reference frame. For example, if you are simulating a fan, you would be able to determine the load on the fan blades.

                Again, I may be wrong and stand to be corrected.

                 

                Also, I've heard that SW Flow Sim may not be able to simulate this type of wind turbine study as it would not drive the motion of the turbine due to the oncoming wind speed.

                 

                David

              • Re: Problem with flow simulation on a vertical axial  turbine (3 blade Giromill)
                Matt Langford

                I think you just need to perform the simulation at multiple rotational speeds. At each speed, calculate the resulting torque. Then you can plot power coefficient vs. tip speed ratio.

                 

                In reality, the turbine will spin at whatever speed it achieves equilibrium; i.e. the aerodynamic torque matches the generator torque. I'm not very familiar with wind turbine generators, but I assume you match a generator to a turbine by selecting one that has a torque curve that is a good match for the turbine's (i.e. extracts maximum power for the expected wind speeds).

                 

                Also, are you sure you want an internal simulation? If you are trying to match a wind tunnel experiment, then you are doing it correctly. If you are trying to match performance outdoors, you should be doing an external flow simulation, using the "Environmental" boundary condition.

                  • Re: Problem with flow simulation on a vertical axial  turbine (3 blade Giromill)
                    David Flemming

                    It is possible to use the Rotating Reference Frame feature to rotate the turbine at multiple rotational speeds, but then you will essentially be defining an angular velocity for the turbine. I'm not too familiar with wind turbines myself but considering that Ijihj is attempting to derive an estimated power curve for the turbine he modeled, then I believe he would want the fluid-structure interaction (FSI) between the wind and turbine blades to provide the torque to turn the turbine. Essentially he may be looking for a Flow-driven CFD approach to this problem.