Example preset
Choose a preset to fill the form and refresh results instantly.
Inputs
Forward (calculate V,Q)
Results
| Cross-sectional area A [m²] | — |
|---|---|
| Wetted perimeter P [m] | — |
| Hydraulic radius R [m] | — |
| Hydraulic average depth Dm=A/T [m] | — |
| Froude number Fr [-] | — |
| Flow regime | — |
| Estimated water depth y [m] | — |
| Iteration details | — |
Cross-sectional view (outline)
Displays the cross-sectional shape according to the input value.
Graph
Display a graph with valid input.
Calculation formula and procedure
R = A / P
V = (1/n) × R^(2/3) × S^(1/2)
Q = A × V
Cross-sectional type (A, P): Supports rectangular, trapezoidal, and circular (partially filled) sections. Solving for depth (Q→y) uses the bisection method, and solving for slope (Q→S) uses an analytical formula.
FAQ
What does the Froude number Fr indicate?
Fr compares inertial and gravitational effects. Fr<1 indicates subcritical flow, Fr≈1 critical flow, and Fr>1 supercritical flow.
What does S (slope) mean?
S in the Manning equation is the energy gradient. For learning, this tool approximates the slope to be approximately equal to the riverbed slope.
Which roughness coefficient n should I use?
The value changes with channel material, vegetation, meandering, and maintenance condition. Preset values are for reference only. For design work, consult the relevant technical documents.
Can the circular cross section results be used for pressure pipes?
No. This tool assumes partially filled open-channel flow with a free water surface, not pressurized pipe flow.
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