Darcy's Law
Darcy's Law
(OP)
I'm hoping that someone can clarify one of the variaibles in Darcy's law. Does the cross sectional area (A) need to be constant over the length (l) in order for the standard equation to work or does a shape factor of sorts need to be applied?
My specific situation involves the design of a sand filter that is contained within a round pipe. The direction of flow is from the center of the pipe to the edge so the cross sectional area parallel to flow is parabolic not rectangular.
My specific situation involves the design of a sand filter that is contained within a round pipe. The direction of flow is from the center of the pipe to the edge so the cross sectional area parallel to flow is parabolic not rectangular.





RE: Darcy's Law
Not sure what you are trying to do. However, perhaps you can take the average of the cross-sectional area across the length.
RE: Darcy's Law
You do not have to consider a radial flow plane. You may consider a vertical flow plane from the center to the edge, having length of R2-R1 and a unit depth.
RE: Darcy's Law
Thanks for your reply. What I'm trying to determine is whether the area (A) normal to the flow needs to be constant over the entire length. For example, say you've got a funnel that has been filled with sand. The area would change from the top to the bottom so would you need to modify the equation to suit, or would it be appropriate to use the average area?
RE: Darcy's Law
RE: Darcy's Law
However, note that on a sand filter, most of the filtration is in the first 2-Inches.
RE: Darcy's Law
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RE: Darcy's Law
Q = HKL2(pi)/LN(R2/R1)
Q = Volume of Flow
H = Head Loss
K = Conductivity
L = Length of pipe
(pi) = 3.14
LN = Natural Log
R2 = Radius of Filter Pipe
R1 = Radius of central inflow pipe