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Figure 1 Hard wheel rolling on and deforming a soft surface, resulting in the reaction force R from the surface having a component that opposes the motion. (W is some vertical load on the axle, F is some towing force applied to the axle, r is the wheel radius, and both friction with the ground and friction at the axle are assumed to be negligible and so are not shown.
μ is the dynamic viscosity of the fluid (Pa·s = N·s/m 2 = kg/(m·s)); Q is the volumetric flow rate, used here to measure flow instead of mean velocity according to Q = π / 4 D c 2 <v> (m 3 /s). Note that this laminar form of Darcy–Weisbach is equivalent to the Hagen–Poiseuille equation, which is analytically derived from the ...
Darcy friction factor formulae. In fluid dynamics, the Darcy friction factor formulae are equations that allow the calculation of the Darcy friction factor, a dimensionless quantity used in the Darcy–Weisbach equation, for the description of friction losses in pipe flow as well as open-channel flow. The Darcy friction factor is also known as ...
Stokes' law is the basis of the falling-sphere viscometer, in which the fluid is stationary in a vertical glass tube. A sphere of known size and density is allowed to descend through the liquid. If correctly selected, it reaches terminal velocity, which can be measured by the time it takes to pass two marks on the tube.
[1] [8], for a wide channel this is approximately equal to the water depth; is the hydraulic gradient, which for uniform normal depth of flow is the slope of the channel bottom [unitless; length/length]; is Chézy's coefficient [length 1/2 /time]. Values of this coefficient must be determined experimentally.
Contents. Moody chart. In engineering, the Moody chart or Moody diagram (also Stanton diagram) is a graph in non-dimensional form that relates the Darcy–Weisbach friction factor fD, Reynolds number Re, and surface roughness for fully developed flow in a circular pipe. It can be used to predict pressure drop or flow rate down such a pipe.
The angle of repose, or critical angle of repose, [ 1 ] of a granular material is the steepest angle of descent or dip relative to the horizontal plane on which the material can be piled without slumping. At this angle, the material on the slope face is on the verge of sliding. The angle of repose can range from 0° to 90°.
The capstan equation[ 1 ] or belt friction equation, also known as Euler–Eytelwein formula[ 2 ] (after Leonhard Euler and Johann Albert Eytelwein), [ 3 ] relates the hold-force to the load-force if a flexible line is wound around a cylinder (a bollard, a winch or a capstan). [ 4 ][ 1 ] It also applies for fractions of one turn as occur with ...