Hydrodynamic pressures in AQWA... more like hydro-dumb-namic pressures?

floatingstonesfloatingstones Member Posts: 5
edited April 19 in Fluid Mechanics

Hello there.

I am simulating a simple cylinder in regular waves (frequency domain) in AQWA - Hydrodynamic Diffraction. Here's a picture of the resulting pressures around the body:

The step on pressures on the free surface doesn't seem right. It also doesn't make sense to me that the largest hydrodynamic pressures are on the free surface... I mean, yes, wave action is larger there, but aren't hydrostatic pressures also included in this value, thus, increasing pressures on the bottom?

Any insight is appreciated :)

Best Answer

  • MikePettitMikePettit Posts: 7Ansys Employee
    Accepted Answer

    Hi floatingstones,

    You're exactly right - hydrostatic pressures are not included in this value. These are hydrodynamic pressure terms only, i.e. incident, diffracted, radiated components plus a hydrostatic-varying component determined from the RAO-based motions.

    The 'Contour Type' in your Pressures and Motions result is set to 'Structure Interpolated Pressure', which is why you see a 'rainbow' just above the water surface. If you switch to 'Structure Panel Pressure' you will see the actual (not interpolated) pressures per panel.

    Generally, the pressures calculated in the Hydrodynamic Diffraction analysis are under the mean wetted surface (only), so you should not expect to see the wave surface shape recreated in the pressure distribution. For the same reason you will also see negative pressure values at some phase angles, where the wave trough passes around the structure.

    I hope this helps! Mike


  • floatingstonesfloatingstones Posts: 13Member

    That helped a lot, @MikePettit. Indeed, when I change the incident wave frequency, I see different patterns of pressures - patterns that I was "expecting". But you are right, not all frequencies and phase angles will present similar patterns. Thank you so much!

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