Please see attachment for the problem. Any hints appreciated. Thank you!
Using the equation Q= K(dh/dx) wouldn't work, because you need the area through which the flow travels (the equation is actually Q =KA (dh/dx). To calculate the hydraulic gradient you would divide the height of the water by the height of the sand: 220/180=1.22 cm. We can use the Kozeny-Carmen equation to find K, with the information given.
Using the Kozeny-Carmen Equation, we have
K = (ρg/ µ) x n^3/ (1-n)^2 x (d^2/180)
n = porosity
ρ =fluid ...