THE FEUTEX TOOLKIT

Part-Full Circular Channel Geometry

Calculate flow area, wetted perimeter and hydraulic radius of a partially filled pipe.

Hydraulics workspace● Runs in your browser

01 Your input

Internal diametermWater depthm

02 Your result

View or copy raw result data

Result data

FormulaCentral wetted angle θ=2acos(1−2y/D); A=D²(θ−sinθ)/8; P=Dθ/2.

Sources and model references

https://www.fhwa.dot.gov/engineering/hydraulics/pubs/08090/hds4_608.pdf

Worked example

Inputs

Internal diameter: 1 m
Water depth: 0.25 m

Expected results

Wetted flow area: 0.1535462123 m²
Wetted perimeter: 1.047197551 m
Hydraulic radius: 0.1466258321 m

Load the example in the workspace to reproduce these results. Display rounding does not change the underlying calculation.

How to use this tool

Enter every input in the labeled units; use measured or independently specified properties.
Check the stated model assumptions before calculating.
Interpret the output as a model estimate and verify it independently for the intended application.

Try this example

{
  "diameter": 1,
  "depth": 0.25
}

Accuracy and scope

Circular section with a free surface; geometry only, not pressurized-flow analysis. Educational engineering estimate only; not structural or safety certification, equipment selection, or operating recommendations.

Is my data uploaded?

This tool runs locally in your browser. Input and output are not sent to a processing server. Copy or download your result before leaving the page.