Froude number definition

This definition of 2VFr is of particular physical significance in film flow, since here the Froude number denotes the ratio of the mean film velocity to the celerity of a gravity wave in shallow liquid. (Wave celerity is defined as the velocity of a wave relative to the liquid on which the wave propagates.) The Weber number is defined by analogy. 

Froude number Fr = fPDIg Ratio of centrifugal to gravity forces used for vortex definition and in gas-liquid mixing correlations... 

Substituting the information given on kinematic viscosity and liquid velocity into the definitions of the Reynolds and Froude numbers,... 

This definition of the linear roughness is difficult to calculate. In a fast flow, the roughness of the pipe or channel wall may be used. Attempts have been made to define a (Nikuradse) sand roughness for closed conduits, such as the ratio of the particle diameter to the inner diameter of the conduit dJD but very little has been published for open channels. The problem is far from simple, and the roughness is often taken as twice the grain diameter. The presence of dunes at low Froude number tends to complicate the picture by introducing another parameter for roughness. 

Assume that microscopic dust settling in air is in the low Reynolds number regime. We start with Stokes s law, Eq. (5.79), to derive an equation for the terminal velocity and substitute the definitions for the Froude number and Reynolds number ... 

The general dependence on the Reynolds, Froude, and Weber numbers appears to be the most useful. In this survey the following definitions of these groups are used ... 

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