Composite Channel Roughness Calculator
Declared Horton–Einstein perimeter-composite Manningn=(ΣP n^1.5/ΣP)^2/3, not area weighted arithmetic roughness or hydraulic flow guarantee. Actual independently established compatible SI units/model context; conditional arithmetic, not code compliance, engineering design or safe operation approval.
Description
A perimeter-composite Manning coefficient uses a stated subsection-combination convention.
A perimeter-composite Manning coefficient uses a stated subsection-combination convention.1
This tool evaluates the supplied Horton-Einstein relation rather than an area-weighted arithmetic average.
When to use Composite Channel Roughness Calculator
Use this tool to evaluate the supplied Horton-Einstein relation rather than an area-weighted arithmetic average.
How to use Composite Channel Roughness Calculator and how it works
- Prepare subsectionWettedPerimeters, callerMatchedManningNs, with the units, conventions and assumptions below.
- Enter the required fields and run Composite Channel Roughness Calculator.
- Read result.value using the output definitions below.
- Correct any rejected inputs and rerun; interpret the result within the stated model and its assumptions.
| Input field | Meaning | Value type | Requirement |
|---|---|---|---|
| subsectionWettedPerimeters | Subsection Wetted Perimeters. Use the units and matching context stated in the calculation below. | array of number | Required; other constraints below |
| callerMatchedManningNs | Caller Matched Manning Ns. Use the units and matching context stated in the calculation below. | array of number | Required; other constraints below |
Supply aligned nonempty arrays of positive wetted perimeter segments and positive Manning roughness values. Return (sum(P*n^1.5)/sum(P))^(2/3) using the selected composite-perimeter convention. Roughness selection and applicability to a particular channel are external.
compositeN=(sum(P_i*n_i^1.5)/sum(P_i))^(2/3) Apply the input ordering, units and branch conditions stated above.
| Output field | Meaning | Value type |
|---|---|---|
| result | Object containing the calculated or selected fields below. | object |
| result.value | Composite Manning n in the input roughness-unit convention. | number |
{
"input": {
"subsectionWettedPerimeters": [
1,
2
],
"callerMatchedManningNs": [
0.03,
0.03
]
},
"output": {
"result": {
"value": 0.030000000000000006
}
}
}Limitations and assumptions
The calculation uses the supplied observations and model inputs. It does not collect measurements, select a reference population or coefficient, or establish that the model applies to the actual case. The stated branch conditions and output units remain part of the result.
All fields require explicit values. Unexpected fields, wrong types, nonfinite numbers and sparse arrays are rejected. Alignment, bounds and supported-token rules are explained above; extremely large inputs or nonfinite results can also fail. Input errors differ from successful false comparisons, unavailable-domain flags and empty match lists.
Alternative or Complementary methods
Use Duct Friction Factor Calculator for a complementary operation: A duct friction factor requires an identified section, Reynolds regime and Darcy or Fanning convention.
Use Equal-Friction Duct Sizing Calculator for a complementary operation: Equal-friction duct sizing depends on flow, roughness, section shape and a chosen pressure gradient.
References
-
Composite Channel Roughness Calculator — tool.io
Similar or alternative tools
- Duct Friction Factor Calculator
A duct friction factor requires an identified section, Reynolds regime and Darcy or Fanning convention.
- Equal-Friction Duct Sizing Calculator
Equal-friction duct sizing depends on flow, roughness, section shape and a chosen pressure gradient.