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The Froude number is based on the speed–length ratio which he defined as: [2] [3] = where u is the local flow velocity (in m/s), g is the local gravity field (in m/s 2), and L is a characteristic length (in m). The Froude number has some analogy with the Mach number.
Dimensionless numbers (or characteristic numbers) have an important role in analyzing the behavior of fluids and their flow as well as in other transport phenomena. [1] They include the Reynolds and the Mach numbers, which describe as ratios the relative magnitude of fluid and physical system characteristics, such as density, viscosity, speed of sound, and flow speed.
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Antidunes occur in supercritical flow, meaning that the Froude number is greater than 1.0 or the flow velocity exceeds the wave velocity; this is also known as upper flow regime. In antidunes, sediment is deposited on the upstream (stoss) side and eroded from the downstream (lee) side, opposite lower flow regime bedforms.
The essence of the actuator-disc theory is that if the slip is defined as the ratio of fluid velocity increase through the disc to vehicle velocity, the Froude efficiency is equal to 1/(slip + 1). [2] Thus a lightly loaded propeller with a large swept area can have a high Froude efficiency.
Efficient displacement hulls travelling at a low Froude number will tend to have a low C p. = Waterplane coefficient (C w) is the waterplane area divided by L WL x B WL. The waterplane coefficient expresses the fullness of the waterplane, or the ratio of the waterplane area to a rectangle of the same length and width.
The wavemaking resistance increases near the critical Froude number, but above it drops significantly. Which is why planing is a desired condition for, for instance, small sail-boats. -- Crowsnest ( talk ) 21:31, 9 April 2009 (UTC) [ reply ]
It is known that the sub critical flow of a stratified fluid past a barrier produce motions upstream of the barrier. Sub critical flow may be defined as a flow for which the Froude number based on channel height is less than 1/π, so that one or more stationary lee waves would be present. Some of the upstream motions do not decompose with the ...