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How does Ansys Aqwa interpolates radiation damping, added mass and force applied on a system?

    • aakashg57
      Subscriber

      Suppose I have a cylinder floating on the water, and I do Hydrodynamic Diffraction analysis to obtain added mass, applied force and radiation damping. Since the added mass, force and radiation damping will only be obtained at a set of frequency values, how does Ansys interpolate the values to generate a smooth curve?

      Furthermore, is there a way to export the data and request Ansys for value of the hydrodynamic coefficients at any frequency within the frequency range of the calculation?

    • Yu Bi
      Ansys Employee
      Hi, you can have more frequency points for the Hydrodynamic Diffraction analysis. Aqwa doesn't export interpolated hydrodynamic coefficient results.
    • aakashg57
      Subscriber
      Hi, I think there is a limit on how many intermediate frequency points that Ansys aqwa can do analysis on. In that case, is the Ansys' way of interpolating the coefficients accessible? I can interpolate them myself if I know what method Ansys uses to interpolate the values.

      Also, I can't seem to export my results of hydrodynamic coefficients. Is there an easy way to get the coefficient values at different frequencies instead of just typing them manually? Thank you!
    • Yu Bi
      Ansys Employee
      Hi, I think you can run the model in multiple projects to have results of more frequencies. You can find the hydrodynamic coefficients in the *.LIS file and *.AH1 file (if you turn on the option to output it) in the solver files directory. Aqwa doesn't use any special interpolation method to interpolate the added mass and damping in hydrodynamic response analysis. You could try cubic interpolation. You can decide the interpolation method depending on the shape of your curves of coefficients.
    • aakashg57
      Subscriber
      Thank you for suggesting an interpolation method. I did have a look at the Analysis.LIS file, but it seems like for the added mass and radiation damping values, only 2 decimal digits are printed. How do you get the exact value with a good number of significant digits.
      And I am not sure how to enable the AH1 file either. Could you please point me to the steps to do that?
      Thanks

    • Yu Bi
      Ansys Employee
      The results exported from Aqwa Workbench can show more digits. *.AH1 can be outputted with the AHD1 option in the *.DAT file. Or in Aqwa workbench, set Yes to ASCII Hydrodynamic Database cell in the Analysis Settings of Hydrodynamic Diffraction, and then the *.AH1 file will be outputted after the solve finishes successfully.
    • aakashg57
      Subscriber
      Apologies for bugging you again, but how do I setup more digits output? In theory, I would like to just copy paste data from the picture I posted. Thank you. I'm new to Ansys.
    • Yu Bi
      Ansys Employee
      No, there is no setting to change the value digit in the output file. The picture you showed doesn't contain the whole matrix. *.AH1 file, the results directly exported from Aqwa Workbench, and the full added mass matrix in the LIS file have more digits in the result values.
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