//Example 8-10 Measuring Flow rate with an Orifice Meter
rho_met = 788.4 //density of methanol at 20C [kg/m^3]
rho_Hg = 13600 //density of mercury [kg/m^3]
mu = 5.875 * 10**-4//dynamic viscosity of methanol [kg/m.s]
D = 4 //diameter of pipe [cm]
d = 3 //diameter of orifice [cm]
h = 11 //differenctial height [cm]
g = 9.81 //gravitational acceleration