Fluids

Fluids

wall shear stress is zero in conical nozzle simulation

    • brmaciel
      Subscriber

      Hello,


      I am still very unexperienced with simulation. I tried to simulate a laminar flow of water in a very small conical nozzle, but I get wall shear stress values equal 0 along the nozzle, and then it suddenly goes up to 3000 Pa at the end (end diameter ~0,2um) - image attached. I suppose the shear stress values should be low at the beginning of the nozzle, but definetely higher than 0. What could be causing that?



       


      Thank you very much in advance.


      Bruna.

    • Rob
      Ansys Employee

      To confirm you're modelling a nozzle with diameter 0.2 microns? 

    • brmaciel
      Subscriber

      sorry, my mistake. 200 microns end diameter = 0.2 mm

    • DrAmine
      Ansys Employee
      If using Fluent solver please check the value there.
    • brmaciel
      Subscriber

      Hi Amine,


      thanks for your answer. Value checked.


      inlet diameter: 4 mm


      outlet diameter: 0.2 mm


      Would you have any idea why I am getting zero wall shear stress?


       


      Thanks and best regards,


      Bruna

    • Rob
      Ansys Employee

      Can you plot the contour (or xy plot in 2d) in Fluent and post that? Also post an image of the near wall mesh. 

    • brmaciel
      Subscriber

      Hi, images are attached.



      contour zoom


       


      mesh:



    • DrAmine
      Ansys Employee

      Please XY Plot the wall shear stress value along the wall (You are working 2D contour plot does not make a sense.

    • brmaciel
      Subscriber

      I plotted it in my first post. Shear stress value along the wall. Here it is again:



       


      Best regards,


      Bruna

    • Rob
      Ansys Employee

      Please can you do the xy plot in Fluent. Also plot a contour of velocity. 

    • brmaciel
      Subscriber

      Here they are:



       




       


      Thanks and best regards,


      Bruna

    • DrAmine
      Ansys Employee
      Can you restrict the plot to smaller range of position? Is your x axis the axis of symmetry?
    • brmaciel
      Subscriber

      What range would you like to see?


      Yes, the x axis is the symmetry axis.


      Best regards,


      Bruna

    • DrAmine
      Ansys Employee
      To 0.04
    • brmaciel
      Subscriber

      If I go to 0.004 in the diagramms, I can see that the shear stress is very low, but not 0. Thanks for the help!


      Best regards,


      Bruna

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