4 Replies Latest reply on Jul 8, 2014 4:44 AM by Jared Conway

    Rotating Cylinder Flow Help

    Thomas Murray
    Thomas Murray Jul 5, 2014 11:10 AM

      Hi All,

       

      I am new to flow simulation in solidworks and have completed many of the tutorials provided by solidworks.

       

      I am having an issue obtaining the correct flow velocity around a cylinder rotating in a fluid (water). It is my understanding that the velocity of the flow at the cylinder edge should be approximately v = R*w (dimensions of cyl are 13.43 in diameter and 1 in in height). But this not what I get. I am getting results close to 1 m/s for a cylinder spinning in water at 150 rpm (15.7 rad/s), when it should be closer to 2.68 m/s.

       

       

      Attached are the images of how I setup the sim.help7.png

      As you can see, there isn't much flow around the cylinder. At the edge it is blue when it should be red/orange. I read another post, and it said to go into component control and disable the revolved cylinder encompassing the object rotating, is this true? I've tried this, and still it dishes out the same results. (Check mark in component control dialog boxes mean the component is included or excluded in flow calcs???) Not sure why I am getting a low flow velocity around the cylinder boundary (not even close to v = r*w)

       

      Pls help,

      SIM_PLS_WORK!

       

      Message was edited by: Thomas Murray

        • Re: Rotating Cylinder Flow Help
          Thomas Murray
          Thomas Murray Jul 5, 2014 8:38 PM (in response to Thomas Murray)

          I have determined a 'workaround' for the problem I am having. If I take a cut plot of velocity perpendicular to the cylinder axis, I get inaccurate values, but if I take a cut plot of velocity parallel to the cylinder axis I get correct values (see new image attached).

           

          Why the two different answers on each cut plot? I mean, clearly where the two cut plots intersect the velocity values should be similar, right?

          help8.png

            • Re: Rotating Cylinder Flow Help
              Jared Conway
              Jared Conway Jul 6, 2014 11:31 PM (in response to Thomas Murray)

              First, The cut plots should match. So I would double check they are plotting the exact same stuff.

               

              Second, have you gone through the refernce docs and kb? This would be best done with a moving wall instead of a rotating region.

               

              What is the end goal of your analysis? Ie the grand scheme?

                • Re: Rotating Cylinder Flow Help
                  Thomas Murray
                  Thomas Murray Jul 7, 2014 11:37 AM (in response to Jared Conway)

                  Hey Jared,

                   

                  Your comment is something that I have been wondering about since I have started with floworks. So, taking a region and rotating it is like spinning the fluid around the object as opposed to the other way around? I have noticed many tutorials spinning the region around impellers rather than spinning the object itself, which made me question this approach. Is it correct to do that, what is the advantage of this, when clearly the impeller is the moving object?

                   

                  In any event, I believe that the problem has been identified. One must select cut plot 'options' drop down box to 'show boundary layer'. When this is done, the profiles match perfectly. Thanks for your reply.

                    • Re: Rotating Cylinder Flow Help
                      Jared Conway
                      Jared Conway Jul 8, 2014 4:44 AM (in response to Thomas Murray)

                      Glad you found the answer, I was pretty sure it was a or setting.

                       

                      Regarding the approach for rotating regions, check out the tech reference. Our method is called frozen rotor, the part stays static and the fluid is spun around it. The other approach is moving mesh which is not part of flow....yet.