Average friction length

An interesting application of the formula (1.43) is the direct deduction of the average friction length A—and consequently the capillary velocity— when the hydraulic resistance R j is known, according to... 

Advances in Contact Angle, Wettabilty and Adhesion Table 1.1 Values of the average friction length for different geometries. 

The results also show that the normalized slip length and the average friction factor-Reynolds number product exhibit Reynolds dependence. Furthermore, the predictions reveal that the impact of the vapor cavity depth on the overall frictional resistance is minimal provided the depth of the vapor cavity is greater than 25% of its width. 

Wind tunnel measurements combined with turbulence theory for hydrodynamic flows influenced by surface friction have led to semi-empirical expressions for the vertical fluctuation of wind speed u = l du/dz and average mixing length / = fc+z (Sutton, 1953). When these formulations are used in conjunction with Eqs. (1-16), (1-28), and (1-30), one obtains rg(z) in terms of wind and friction velocities ... 

The continuous reading, fixed slip technique is similar to the abovementioned locked wheel skid tester technique but it provides a record of skid resistance along the whole length of the test track surface. It also enables averages to be obtained for specified test segments. Hence, the instantaneous friction reading is recorded and the BFC for each friction length is calculated and recorded. 

The difference between and is more pronounced with d-PBT sample, and is b ieved to represent the effects of heterogeneity caused by molecular association. The result gin20/2 = 135 ys at infinite dilution is attributed to the unassociated species such that the molecular friction coefficient is given by HO/ng = 70.7 nm (the solvent viscosity rig is 9 mPa s at 25 ). For rodlike chains, the weight average contour length Lyj is given by ... 

Friction Factor and Reynolds Number For a Newtonian fluid in a smooth pipe, dimensional analysis relates the frictional pressure drop per unit length AP/L to the pipe diameter D, density p, and average velocity V through two dimensionless groups, the Fanning friction factor/and the Reynolds number Re. 

For commercial pipe with roughness e = 0.046 mm, the friction factor is about 0.0043. Approaching the last hole, the flow rate, velocity and Reynolds number are about one-tenth their inlet values. At Re = 16,400 the friction factor/is about 0.0070. Using an average value of/ = 0.0057 over the length of the pipe, 4/Z73D is 0.068 and may reasonably be neglected so that Eq. (6-151) may be used. With C, = 0.62,... 

Total equivalent length of pipe (assuming that every fitting has an average 5 m of equivalent pipe length, to account for friction) = 1000 + 25 X 5... 

A man of weight 100 kg standing on skis 2 m long and 0.10 m wide slides on the 2° mountain slope, at 0°C. Calculate the work done against friction when the ski slides a distance equal to its own length. Hence calculate the average thickness of the water film beneath each ski. (The latent heat of fusion of ice is 330 MJ m °.)... 

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