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Friction losses typically increase with an increasing wetted perimeter, resulting in a decrease in head. [1] In a practical experiment, one is able to measure the wetted perimeter with a tape measure weighted down to the river bed to get a more accurate measurement. When a channel is much wider than it is deep, the wetted perimeter approximates ...
where x is the space coordinate along the channel axis, t denotes time, A(x,t) is the cross-sectional area of the flow at location x, u(x,t) is the flow velocity, ζ(x,t) is the free surface elevation and τ(x,t) is the wall shear stress along the wetted perimeter P(x,t) of the cross section at x.
P is the wetted perimeter of the cross-section. More intuitively, the hydraulic diameter can be understood as a function of the hydraulic radius R H, which is defined as the cross-sectional area of the channel divided by the wetted perimeter. Here, the wetted perimeter includes all surfaces acted upon by shear stress from the fluid. [3]
Units of n are often omitted, however n is not dimensionless, having dimension of T/L 1/3 and units of s/m 1/3. R h is the hydraulic radius (L; ft, m); S is the stream slope or hydraulic gradient, the linear hydraulic head loss loss (dimension of L/L, units of m/m or ft/ft); it is the same as the channel bed slope when the water depth is ...
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The wet-bulb temperature is the lowest temperature that may be achieved by evaporative cooling of a water-wetted, ventilated surface.. By contrast, the dew point is the temperature to which the ambient air must be cooled to reach 100% relative humidity assuming there is no further evaporation into the air; it is the temperature where condensation (dew) and clouds would form.
Figure 2: Wetting of different fluids: A shows a fluid with very little wetting, while C shows a fluid with more wetting. A has a large contact angle, and C has a small contact angle. The contact angle (θ), as seen in Figure 1, is the angle at which the liquid–vapor interface meets the solid–liquid interface, and is determined by the ...
The Exner equation describes conservation of mass between sediment in the bed of a channel and sediment that is being transported. [1] It states that bed elevation increases (the bed aggrades) proportionally to the amount of sediment that drops out of transport, and conversely decreases (the bed degrades) proportionally to the amount of sediment that becomes entrained by the flow.