Anonymous
Anonymous asked in 科學及數學工程學 · 1 decade ago

About Darcy's Equation

Darcy's Equation:

h[f]=4f(L/D)(rho*u^2/2g)

Have anyone known the meaning of 'L/D' in Darcy's Equation???

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  • 1 decade ago
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    If this equation refers to problems of the pile flow, you don't have to focus on this term or ratio or even the physical meaning.

    Basically, you can split L/D to study this equation:

    1: L --> Length of the pipe or the length of a particular section where you are interested in. As there is friction on the internal surface of the pipe and the water near the internal surface has to overcome the friction, energy must lose. So you can see that h is directly proportional to L since longer a pipe is, more energy is lost.

    2: D --> Internal diameter of the pipe. However, you can interpret the “D” as the measure of the relatively roughness of the wall to the water flow. As the pipe is larger, the “relatively amount” of water affected by the water is less. Bear in mind that the water adjacent to the wall flows much slower than the water in the region of the centre of the pipe (if the velocity of flow is low). In addition, if the internal surface is very very rough, there is a layer of water adjacent to the wall flows turbulently-->energy is lost. Finally, the effects of the wall roughness to the flow of water decreases with water being further away from the wall.

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