5 Replies Latest reply on Oct 3, 2009 2:27 PM by Bill McEachern

    Strouhal number

    Idspl Support
      can anybody know how can we find out the strouhal no in flow simulation????????
        • Re: Strouhal number
          Brian Zias
          Strouhal number is reportable, but it probably isn't enabled by default so that's why it isn't showing up as an option when post-processing. Open up the parameter list in your project and enable that parameter (Flow Simulation > Results > Parameter List...)
            • Re: Strouhal number
              Idspl Support
              i already checked the parameter list but there is no option  for strouhal number.
                • Re: Strouhal number
                  David Paulson

                  It would be very helpful if you could provide some information on the significance of the Strouhal Number to the problem that you are trying to solve.  In my practice, I have never utilized a Strouhal Number, but that does not mean that the function should not be integral to Flow Simulation.  If you can provide a little more information about your application, I am sure that you can enlighten not only those of us on the forum, but more importantly the program developers at SolidWorks.

                   

                  And the members of this forum may be able to suggest a work-around that may provide good results as well.

                    • Re: Strouhal number
                      Bill McEachern

                      Sicne you rnot gettig anything I will offer the following:

                      Smoke stack - need to get the range of frequencies it will expereince due to vortex shedding

                      Heater in a cartridge is singing - see if frequency of vortex shedding lines up with natrual mode of vibration of heater and sound heard - and yes it did.

                      UV light in a reactor with a cross flow - sam ething ensure the natural modes don't line up withthe dominant shedding frequencies.

                       

                      Pretty handy really but like I said I don't think this is a reasonable question for a time averaged NS code to pump out a number or a plot of Strouhal number,  though it can certainly show you the shedding vortices in time and you can count them up. Flow does a beautiful job at this in my experience..

                • Re: Strouhal number
                  Bill McEachern

                  From Hoerner Fluid Dynamic Drag, Stouhal # is defined as S=fd/V......Where f=frequency, d= characteristic length & V= velocity. Thus it would seem to me, that the plotting of Strouhal number would require that frequencies be known, not to mention the what the characteristic length of interest is.  Considering the former, to get Strouhal # you would need a transient analysis and it would be a parameter integrated in time and direction would also be relevant- you would need to count frequencies to get them. Frequencies maybe available as an instaneous value but it seems not so likely considering a wall model is used. Maybe some one more knowledgeable could comment on obtaining frequency directly. Spectral methods maybe? You may want to check the area of the code that deals with quantities integrated in time but I am not optimistic. Flow simulation uses the time averaged approach to the solution of NS equations so even a so called "steady state" solution has evolved in "time" providing some hope that the if it was available it may not be study type dependent.....

                   

                  I did a search of the technical reference document and it returned the flow over the cylinder case in the validation section when Stouhal number was put in. It shows that Flow sim produces a good estimate of the frequency (period) as function of R'number. It should be noteworthy that no spatial plot of Strouhal number was shown in the example. I did this same problem once before and I counted the vortex shedding from the temporal animation.

                   

                  My guess is getting a Stouhal number plot is not a reasonable request from the code - just due to what it is.

                  Ciao,

                  Bill