5 Replies Latest reply on Apr 27, 2017 9:09 AM by Txon Aguirre

    Parametric studies results for a propeller

    Txon Aguirre

      Im working with a CPP(Controllable Pitch Propeller) using a parametric study, where for each pitch, RPM changes along a given range.

      No problem at this stage. But ...

      For some values(pitch and RPM combinations), very odd results are obtained. Hence I built a single project for those strange values and ..... Here is where my doubts arised.

       

      The parametric study gives only "averaged values" for Thrust and Torque of the prop, while the single simulation returns "Value" and "Averaged Value". What is the good solution ?  How to get "values" in the parametric study ?  Diference between "averaged" and "value" are quite big.

      As I think that "averaged value" is related to "all" values obtained in all the iterations, and "value" is the final "best fit", obviously the later is the correct solution. If parametric studies are unable to return "VALUES" I don't get what are they useful for.

       

      Thanks in advance

        • Re: Parametric studies results for a propeller
          Seckin Uslu

          The correct results are values. Averaged values are all values iteration from start to end. I dont know parametric study gives VALUES,

           

          Instead of parametric study, you can clone study for different configurations.Also SW Flow has batch run functionality.

          • Re: Parametric studies results for a propeller
            Bill McEachern

            uJust to be clear: under Values is the value of the last iteration. Under average value is the averaged value of the value of each iteration over the last analysis interval. The min and max values are the min and max values recorded under values within the last analysis interval. The analysis interval is the number of iteration considered in the determination of convergence. In a steady state analysis the value and the average value will typically be close. At least that is my understanding and if you look it up in the Documentation it will say substantially the same thing.

            • Re: Parametric studies results for a propeller
              Txon Aguirre

              Hi all again:

              I found where the results (VALUES) are in the parametric studies, thanks a lot. Anyway ....

               

              The propeller under study is, as I pointed above, a CPP being designed for a ROV propulsion. Hence it is a little sized one (D=70mm).

              The Pitch range in our study runs from 00º to 35º and RPMs from 3000 to 4500, resulting on Re for 70%R from 3.3E5 to 4.8E5 at the design advance speed.

              When the parametric study is run, mainly in the case for Pitch=20º, very odd results are returned for some RPMs.

              In order to check for those strange values, the project was cloned and a single study performed for those given conditions. This way, values agree with what was expected.

              It must be said that the diference between both calculations is big, being one of them four times the other.

               

              Therefore .............. If for some conditions, the difference between a parametric study and a single one is so big ...... How to trust on all other parametric results ?