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This formula implies that the group velocity of a deep water wave is half of its phase velocity, which, in turn, goes as the square root of the wavelength. Two velocity parameters of importance for the wake pattern are: v is the relative velocity of the water and the surface object that causes the wake.
Hull speed can be calculated by the following formula: where is the length of the waterline in feet, and is the hull speed of the vessel in knots. If the length of waterline is given in metres and desired hull speed in knots, the coefficient is 2.43 kn·m −½.
In shallow water, the group velocity is equal to the shallow-water phase velocity. This is because shallow water waves are not dispersive. In deep water, the group velocity is equal to half the phase velocity: {{math|c g = 1 / 2 c p. [7] The group velocity also turns out to be the energy transport velocity.
Stokes drift under periodic waves in deep water, for a period T = 5 s and a mean water depth of 25 m. Left: instantaneous horizontal flow velocities. Right: average flow velocities. Black solid line: average Eulerian velocity; red dashed line: average Lagrangian velocity, as derived from the Generalized Lagrangian Mean (GLM).
The group velocity is positive (i.e., the envelope of the wave moves rightward), while the phase velocity is negative (i.e., the peaks and troughs move leftward). The group velocity of a wave is the velocity with which the overall envelope shape of the wave's amplitudes—known as the modulation or envelope of the wave—propagates through space.
The phase velocity c p (blue) and group velocity c g (red) as a function of water depth h for surface gravity waves of constant frequency, according to Airy wave theory. Quantities have been made dimensionless using the gravitational acceleration g and period T, with the deep-water wavelength given by L 0 = gT 2 /(2π) and the deep-water phase ...
By measuring the level of water remaining in the vessel, the time can be measured with uniform graduation. This is an example of outflow clepsydra. Since the water outflow rate is higher when the water level is higher (due to more pressure), the fluid's volume should be more than a simple cylinder when the water level is high.
The TKE can be defined to be half the sum of the variances σ² (square of standard deviations σ) of the fluctuating velocity components: = (+ +) = ((′) ¯ + (′) ¯ + (′) ¯), where each turbulent velocity component is the difference between the instantaneous and the average velocity: ′ = ¯ (Reynolds decomposition).