5 Replies Latest reply on Oct 9, 2017 3:44 AM by Mark Keown

    impossible to select my propeller for rotation

    Eric Benessy

      Hi,

       

      It seems they are the blades which cause the problem : if I erase the blade and only select the central axis of the propeller, it works ????

       

      The blades are a simple circular pattern of a loft with SW2017.

       

      In addition : if I select  "global rotating" with the blades it works; maybe it could help you to help me to get "local region(s)" to work...

       

      several hours to try anything to solve the problem before asking help to you ;-)

       

      Thanks by advance,

        • Re: impossible to select my propeller for rotation
          Mark Keown

          Go to Help, SolidWorks Simulation, Flow Simulation Online tutorial and find examples.

          In Flow the rotating region is what rotates - NOT the impeller or blade.

           

          • Re: impossible to select my propeller for rotation
            Ryan Dark

            Hi Eric,

            Like Mark Keown pointed out, the blade itself is not what rotates in the Flow Simulation calculation.  You would extrude a circular boss around the hub and blades that would become the local rotating region.  It is like you see in this similar thread (Solidworks won't recognize propellers in flow simulation).

              • Re: impossible to select my propeller for rotation
                Eric Benessy

                ok I have seen my "mistake" but what is the purpose to the use of a circular boss part instead of directly use the objects in rotation ???

                 

                Project(1).png

                Project(1)_1.png

                 

                In order to be sure if I've right processed : does the inverse ( red squared ) flow is normal ?

                I guess yes as there is a gap between the blade and the duct but I prefer to ask

                  • Re: impossible to select my propeller for rotation
                    Ryan Dark

                    The origin of Flow Simulation is that the object itself is static and the flow is being defined to move around the static object as though it were a moving object.  So, that is the origin of creating the cylindrical boss in order to tell the fluid to rotate around the static propeller..

                     

                    Looking at your flow it seems fine.  You may need to bring the shroud in closer to the propeller to stop seeing that back flow though.  If the rotating region is beyond the tip of the blades then it is positioned fine itself.

                      • Re: impossible to select my propeller for rotation
                        Mark Keown

                        If you configure for Local Region Sliding - then you will see the blade rotate each time step.  So the blade is rotating NOT the fluid.

                        However when the solver initially starts (time = 0) the fluid is rotating but as it solves you will see the blade move and the proper flow develop.

                         

                        Yes you will get flow out both directions with that type of blade.  Look at the steep blade pitch - the flow is more radial that axial so the flow is goring to the point of least resistance -- to the low pressure area.  You can observe this with a turbo axial fan if you have one.  Hold a thin long strip of Kleenex with tweezers and move it across the front of the fan (inlet of the fan).  You may observe the flow reverses at some points near the OD and near the hub.

                         

                        When using Local Region Sliding expect the solve to be over night.

                        - start with the time step about 1/20 of the period for about 6 revelations of the blade.

                        - then switch to auto time step.

                        - configure the shroud as a stator (Boundry condition, Real wall and tick the stator box, select the shroud part)

                         

                        Cheers