Open Channel Flow Calculator — Manning’s Equation & Hydraulic Calculations

Open Channel Flow Calculator

Calculate flow rates, velocities, and hydraulic parameters for open channels using Manning’s equation. Perfect for civil engineering, hydrology, and drainage design projects.

Step 1: Channel Geometry

z = 0

Channel Geometry Notes

For rectangular channels: z = 0. For trapezoidal: z = horizontal/vertical ratio. For triangular: B = 0, z > 0.

Step 2: Hydraulic Parameters

Manning’s Equation

Q = (A * R^(2/3) * S^(1/2)) / n
Where: Q = Flow rate, A = Cross-sectional area, R = Hydraulic radius, S = Slope, n = Manning’s roughness coefficient.

Open Channel Flow Calculation Results

Summary
Hydraulic Parameters
Flow Analysis

Flow Rate (Discharge)

3.672 m³/s
Mean Velocity: 1.836 m/s
Cross-sectional Area
2.00 m²
Wetted Perimeter
4.00 m
Hydraulic Radius
0.50 m
Froude Number
0.83

Hydraulic Parameters

Top Width (T)
2.00 m
Water surface width
Hydraulic Depth (D)
1.00 m
A / T
Section Factor (Z)
1.41
A * √D
Conveyance (K)
3672
m³/s per slope unit

Flow Classification

Subcritical flow: Fr < 1 (slow, tranquil flow). Critical flow: Fr = 1. Supercritical flow: Fr > 1 (fast, rapid flow). Your calculated Froude number indicates subcritical flow conditions.

Flow-Depth Relationship

Manning’s Equation Formula

Q = (1/n) × A × R^(2/3) × S^(1/2)

Where:
Q = Flow rate (discharge)
n = Manning’s roughness coefficient
A = Cross-sectional area of flow
R = Hydraulic radius (A/P)
S = Energy slope (channel slope for uniform flow)
P = Wetted perimeter

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