Product(s):	MAXSURF Motions
Version(s):	23.07.00.268
Area:	Panel Pressure

Problem

What is the wave amplitude used in the panel pressure during animation?

Solution

If the regular waves was selected from the Calculate Wave Surface dialog (Analysis | Calculate Wave Surface), then the displayed pressure in the animation will use the “wave amplitude” displayed in the dialog.

The pressure = “Magnitude” * rho * g * wave_amplitude

But the animation in Irregular Waves should be taken as a “guide” only. If using irregular waves:

Then Motions splits the wave spectrum into the number of specified wave components.
Instead of using equally-spaced in frequency waves, the frequencies are selected so that they have approximately the same energy.

The pressures are computed by summing the contributions of each wave frequency, allowing for the random phasing of the different wave frequencies.

But again the pressure contribution for each frequency is given by
Pressure(frequency_i) = “Magnitude”(frequency_i) * rho * g * wave_amplitude(frequency_i)

Because the frequencies at which the panel method was evaluated do not necessarily match the frequencies used when splitting the wave spectrum, Motions uses the pressure of the closest computed frequency (it doesn’t interpolate)

So the pressure scale for the irregular waves animation, this is quite approximate because it simply looks at the max/min pressures at the computed frequency closest to the wave spectrum modal (T_bar) frequency of the wave spectrum and the regular sinusoidal wave amplitude with the same energy as the whole spectrum: sqrt(2 * m0)

See Also