8 Replies Latest reply on Mar 9, 2013 12:02 PM by Wernyu Hau

    Thrust of Marine Propeller & Computational domain

    Wernyu Hau

      Hai everyone,

       

      could anyone tell me the way to obtain the thrust of MARINE propeller by using the flow simulation of solidworks?

      Also, how to calculate the fluid domain that is suitable for my simulation works?

       

      please help.

       

      thank you.

       

      regards,

      wernyu

        • Re: Thrust of Marine Propeller & Computational domain
          Jared Conway

          Hi Wernyu, we completed this type of project only a couple months ago for a customer. The results actually came out very close to what they were expecting once they completed the physical testing.

           

          For the thrust, similar to the tutorials on obtaining drag, you simply need to select ALL of the faces of the propeller and choose the force component in the direction of flow. That will provide you the thrust value.

           

          For fluid domain, check the SolidWorks knowledgebase. There is a good article on computational domain for aerodynamic flow. The pointers are basically the same. The computational domain should be large enough that the main flow does not cross a boundary condition. Start with 2 diameters to the top and side and front and 4 in the back and go from there. A really coarse mesh will help with this.

            • Re: Thrust of Marine Propeller & Computational domain
              Wernyu Hau

              Hi Jared. So, it means i shall use surface goal rather than volume goal to determine the thrust right?  I did notice from a thesis that they calculate the propeller with blade then add up again with the propeller without blade for the force (they use solidworks cosmos floworks also).  Mean after force (hub c/w propeller blade), then re-calculate and add up with force (hub only). They used global goal for the propeller that convert from Rhino. 

               

              sorry for additional question, do we just simply get the torque from the global goal in the rotational axis also? what about advanced velocity, Va? are you measured it using volume goals for velocity in forward motion of propeller?

               

              thank you so much for you esteem reply.

              regards,

              wernyu

                • Re: Thrust of Marine Propeller & Computational domain
                  Jared Conway

                  surface goal...yep!

                   

                  Can you link the thesis you're describing so that I can take a look at it. Their method sounds reasonable. Setup the project with the prop, setup the project without the prop. Select all the faces on both analyses and determine the force. Subtract one from the other and you can determine the force from the prop only. This seems like a good method. My guess is they are making sure that they have a closed surface for the force calculation. If you have an open surface (for example trying to read the force on a single prop) the results might not be correct.

                   

                  For torque, I'd just go with another surface goal using the appropriate axis. If you're selecting all the faces for the surface goal and there is nothing else in the model, the global goal for thrust should be the same as your surface goal. For torque, I'm not sure, but it should probably be.

                   

                  You're going to have to give me some more info on advance velocity. I'm not sure what you' trying to measure there.

                    • Re: Thrust of Marine Propeller & Computational domain
                      Wernyu Hau

                      of course, Jared.  Here you go,

                      http://collections.mun.ca/PDFs/theses/Wu_Xueyin.pdf

                      because i am doing my thesis also, thus i need some related information which is closest. 

                      For marine propeller analysis, Kt, Kq and J are important data in order to measure and compare for the optimum data(3 data in one graph). 

                      for J(advanced coefficient) you need the Va, advanced velocity. 

                      Jared, he was not substracted it but ADD it, that's what i am confusing also.  i did read about the CFD method in ITTC also, but forget which PDF, it's a correct method if referring to their approach in obtaining the thrust

                        • Re: Thrust of Marine Propeller & Computational domain
                          Jared Conway

                          Hi Wernyu, since we are considering the propeller fixed and the fluid flowing around it, you'll need to find out how Va is measured in that type of physical test. If I understand the PDF correctly and this wiki reference http://en.wikipedia.org/wiki/Advance_ratio, Va is the velocity at which the device would move forward. So it might be a good assumption to use the average velocity in and around the prop. Or figure out from the force/volume flow rate what speed it would drive things forward. The only way to really find it would be to using a moving mesh solution where the prop actually moved something to figure out the velocity. I didn't see anything specifically in the PDF on how the Va was measured in flow. (That being said, I scanned it vs reading thouroughly. If you can point me to a section, I can review further).