CivilToolbox Manning Pipe

Solve For:

Pipe Parameters (Input Values)

Inside Pipe Diameter D=
Depth of Flow in Pipe d=	in
Slope of Pipe S_o=	^ft /_ft
Relative Pipe Roughness n=
Flow Q=	cfs

Output

Pipe Discharge    Q=^1.49⁄_n A_w R_h^²⁄₃ S_o^½
= ^1.49⁄_0.013 (0.349)(0.167) ^²⁄₃(0.005)^½
= 0.854 cfs = 552,261 gpd

Pipe Flow Velocity    V = ^Q⁄_{A_w} = ^0.854⁄_0.349 = 2.448 ft/s

Percent Full (Volume)    % = ^A_w⁄_{A_t} = ^0.349⁄_0.349 = 100%

Percent Full (Depth)    % = ^d⁄_D = ^0.667⁄_0.667 = 100%

Manning Equation Variables

Wetted Area of Flow A_w=½r² (α-sinα)
= ½(0.333) ²(6.283 - sin 6.283)
= 0.349 ft²

Wetted Perimeter P_w=rα=0.333 ft x 6.283
= 2.094 ft

Hydraulic Radius R_h=^A_w⁄ _{P_w}=^{0.349
ft
²} ⁄ _{2.094
ft}
= 0.167ft

Pipe Geometry Variables

Inside Radius of Pipe    r = ^D⁄₂ = ^0.667⁄₂ = 0.333 ft

Flow Depth - Pipe Radius    h = d - r = 0.667 - 0.333 = 0.333 ft

Angle #1    θ = arccos(^h⁄_r) = arccos(^0.333⁄_0.333) = 0 rad

Angle #2    α = 2 π- 2 θ = 2 π - 2(0) = 6.283 rad

Total Inside Pipe Area    A_t = π r² = π(0.333)² = 0.349 ft²