1 Reply Latest reply on Dec 26, 2013 11:48 AM by Jared Conway

    More RPM is needed than real test for a same thrust.

    Sj Jung

      Hi I'm simulating rotating propeller in duct shroud. (external/rotating region/16000RPM/below mach1)

       

      What I found was when I want to make same thrust as real test I need more RPM of... about 150% of real test.(after very sufficient 18travel and 1500iteration.)

       

      every stream line and pressure contour is plausable..

       

      I make every prop and parts very pricisely with SW.

       

      Would it be there any mistakes in my test? or is it just inevitable gap between computer vs real situation..??

       

      I should try internal analysis?

       

      One more question.

       

      When a stream of air flows through one face of computational domain(from outside of domain to inside), what is their boundary condition? Does Flow Simulation just calculate domain's outside as infinite air space?

       

      Thanks for helping me.

       

      By the way if you need files I'll attatch it (Now I'm in my working place )

        • Re: More RPM is needed than real test for a same thrust.
          Jared Conway

          how many parameters from the real test do you have to compare to the simulation? with just one you'll have a hard time knowing if it is a setup problem or a sim vs physical problem. but 150% is pretty far off, i'd guess setup unless there is something about your prop that causes the KE method to break down. do you have a reseller you can work with on this? to get the developers to check your application?

           

          that being said, you haven't told us much about your setup or your physical test to make sure that they are the same. this is the key in this investigation.

           

          then the next is to make sure that you've done everyhting you can to eliminate numerical issues. for example you're asking about the comp domain, have you confirmed that the results don't change when you make it bigger? have yo ufollowed all the recommendations in the KB for rotating regions? have you confirmed a mesh independent solution?