Reynolds number, local

The wall shear can be determined from a friction factor /, which depends on the local Reynolds number... 

The wall friction zw may be evaluated in terms of a friction-factor correlation based on a local Reynolds number. 

At any distance, x, from the leading edge, the local Reynolds number will be given... 

Fig. 26. The velocity profile for flow of water through two different regions (highlighted in Fig. 25a) of the inter-particle space within a fixed bed of spherical glass beads. The velocity profiles are measured across the inter-particle space between two packing elements. Profiles are shown for local regions associated with fast and slow flow velocities, characterised by a local Reynolds number of 50 and 12, respectively. At low Re number, a parabolic flow profile typical of Poiseuille flow is seen (----). At the higher Re number, inertial effects in the flow are evident and the flow profile approaches that of plug flow (-------). For this particular bed, the Re number based on bed diameter is...

The local Reynolds number Re = 2rU/v used in the studies of EPRs varies between 100 and 2 000, so that one often takes n = 1/3, m = 1/2, and C = 0.6. The Prandtl and Schmidt criteria express the properties of interacting substances. For the systems heat in air and water vapour in air , they are Pr = (vp1cp)/A 0.7 and Sc = v/D 0.6 [60], Having transformed these basic empirical relations, Berman [60] suggested a relation for spraying systems aE = 3 U/2r, provided the local velocity U is taken in m/s and the droplet diameter 2r in m. The latter was used in the following performance ofSCSs. 

The working range of the local Reynolds number can be estimated as 1000 < Re < 30000, so the vortices behind individual obstructions are still ordered with only... 

Some paradoxes of the turbulence in canopies, or EPRs, were pointed out by Raupach and Thom in their state-of-art review of 1981, [522], The first phenomenon is the value of the drag coefficient of elements that constitute the EPR. The highly precise measurements in aerodynamic tubes brought values that depend on the obstacle shape, the flow turbulence level, and the mutual disposition of obstacles but vary near cf 0.5 for spheres and cf 1 for cylinders in the working range of the local Reynolds number 103 < Re < 105. The same coefficient determined from the field measurements in forests turned out to be several times less (in this case, the indirect calculations were performed). A similar paradox takes place for the exchange coefficients. 

Two local Reynolds numbers can thus be formed based on the characteristic velocity and length scales for the boundary layer. One Reynolds number purely based on the viscous scales of the inner layer, v dvji/, is identically unity, and the alternative dimensionless group called the friction Reynolds... 

Notice that j/+ is very similar to the two local Reynolds numbers just defined for the boundary layer, thus the magnitude of this dimensionless length variable is sometimes interpreted as a kind of Reynolds number. 

Rex = UaoX/v being the local Reynolds number. Here, the wall friction (resulting from the momentum flow retarded in the boundary layer) may be evaluated from ... 

Reynolds number in pipe, DVpIfx Maximum local Reynolds number in pipe,... 

For packed beds of spheres, the porosity is generally larger near the bounding solid surface, resulting in an increase in the local velocity (component parallel to the surface) and the local Reynolds number. 

The resulting expression relates the local Sherwood number to the local Reynolds number, the Schmidt number, and the parameter p. A second equation relating these quantities results from the condition that the interface is impermeable to the noncondensable gas... 

Re, local Reynolds number = ullv, defined as used... 

Re local Reynolds number based upon free stream velocity = U xlv... 

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