Streamline Flow through Curved Pipes

C, a numerical coefficient , defined, as F d /8 μv representing the increase of resistance due to curvature, d , diameter of pipe. D, mean diameter of coil. d /D, curvature ratio. F, intensity of frictional drag on wall of pipe, i. e ., shear stress at boundary, g , gravitational acceleration, m , hydraulic mean depth, = area/perimeter, v , mean velocity of flow, = volume flowing per unit time/cross sectional area of pipe, ρ , density of fluid, μ viscosity of fluid. All the values given in the paper are dimensionless, except in those cases in which some dimension is specifically stated.