Community Computational Fluid Dynamics Results analysis Regarding the calculation of KCS resistance

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Regarding the calculation of KCS resistance

Halder

I am working on the simulation of the ship modelling. I am using the FINE/Marine software for ship model calculation. Therefore, I am following the tutorial “KCS resistance calculation”. However, I have taken geometry from the FINE/Marine tutorial folder “KCS_hull_SVA_cf_withnames_cf2”. After that I used the model scale without a rudder (1:31.6). Next step I followed the same procedure as mentioned in the report. I have simulated six velocities (0.915m/s-2.379m/s) corresponding to the Froude number and compared them with the results without the rudder at velocity 2.196m/s. In my CFD results I got a Ct value of 3.44*10^3 (Fx=82.24N, wetted surface=9.9206m^2, density 999.1kg/m^3, V=2.196) while the reference Ct value is 3.551*10^3 corresponding velocity 2.196m/s). I am getting a lower Ct value as compared to the FINE/Marine CFD results. So, I am worried about getting a lower Ct value. Therefore, I am requesting you to kindly help with the calculation so I can get similar results as mentioned in the KCS resistance calculation.

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  • +1

    Hi,

    I am sorry to see that nobody took the time to check your request since a couple of months... Let me try to help you if not too late.

    If I understand correctly, you followed the tutorial about the KCS but you scaled down all data using the C-Wizard with a ratio 1/31.6. At the end, you observed a difference in Ct about 3% compared to the full scale results provided by CFD as well. Correct?

    I am not really surprised by this difference. It is known that the scaling up/down results is always very risky since turbulence does not act the same way at both scales (indeed, we preserve the Froude number but not the Reynolds number). Also, the scale is here very large and the more we scale, the more difference we can get.

    Does that make sense for you?

    Best regards,

    Benoit

Reply
  • +1

    Hi,

    I am sorry to see that nobody took the time to check your request since a couple of months... Let me try to help you if not too late.

    If I understand correctly, you followed the tutorial about the KCS but you scaled down all data using the C-Wizard with a ratio 1/31.6. At the end, you observed a difference in Ct about 3% compared to the full scale results provided by CFD as well. Correct?

    I am not really surprised by this difference. It is known that the scaling up/down results is always very risky since turbulence does not act the same way at both scales (indeed, we preserve the Froude number but not the Reynolds number). Also, the scale is here very large and the more we scale, the more difference we can get.

    Does that make sense for you?

    Best regards,

    Benoit

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