Compute geometry relations for trapezoidal channels.

channel_geom(y, B, SS)

## Arguments

y Flow depth [$$L$$]. Channel bottom width [$$L$$]. Channel sideslope [$$L L^{-1}$$]. For a rectangular channel, SS = 0.

## Value

Named vector:

A

Flow area [$$L^2$$].

P

Wetted perimeter [$$L$$].

R

Hydraulic radius [$$L$$].

Water surface width [$$L$$].

dPdy

First derivative of wetted perimeter w.r.t. flow depth.

dRdy

First derivative of hydraulic radius w.r.t. flow depth.

DH

Hydraulic depth [$$L$$].

ybar

Vertical distance from water surface to centroid of flow area [$$L$$].

## Details

Channel geometry relations are routinely calculated in numerical solutions of steady, gradually-varied and unsteady flows. This function is used extensively by internal procedures and is made accessible to the user for convenience.

## Examples

channel_geom(1.71, 100, 0) # rectangular channel#>           A           P           R        dAdy        dTdy        dPdy
#> 171.0000000 103.4200000   1.6534519 100.0000000   0.0000000   2.0000000
#>        dRdy          DH        ybar
#>   0.9349555   1.7100000   0.8550000 channel_geom(5.79, 6.1, 1.5) # trapezoidal channel with sideslope 3H:2V#>          A          P          R       dAdy       dTdy       dPdy       dRdy
#> 85.6051500 26.9761419  3.1733652 23.4700000  3.0000000  3.6055513  0.4458854
#>         DH       ybar
#>  3.6474286  2.3281400