Channel Studio offers three different methods for computing friction losses. These options are selected on the Compute tab as shown below.
In general, friction loss is computed as the product of Sf and the discharge-weighted reach length, L. The friction slope (slope of the energy grade line) at each cross section is computed as follows:
Average Conveyance
This is the default method used and is known to provide the best overall results compared to the Average Friction Slope and Geometric Mean.
Where:
Sf = Friction slope
Q = Total flow at the cross-section
K = Total conveyance at the cross-section
Average Friction Slope
Use this method when you are dealing with channels at steeper slopes, subcritical and supercritical profiles.
Where:
Sf = Friction slope
Sf1, Sf2 = (Q/K)^2
K = Total conveyance at the cross-section
Geometric Mean
Use when working mainly with supercritical flow profiles.
Where:
Sf = Friction slope
Sf1, Sf2 = (Q/K)^2
K = Total conveyance at the cross-section
Conveyance
Conveyance, K, is computed as:
Where:
Cm = Manning Coefficient = 1.486 (1.00)
n = Roughness coefficient
A = Cross-sectional area of flow
R = Hydraulic radius = Area/Wetted Perimeter