# Creates a specific energy diagram for a trapezoidal channel

Source:`R/spec_energy_trap.R`

`spec_energy_trap.Rd`

This function plots a specific energy diagram of a trapezoidal (including rectangular and triangular) channel, with annotation of critical depth and minimum specific energy.

## Usage

```
spec_energy_trap(
Q = NULL,
b = NULL,
m = NULL,
y = NULL,
scale = 3,
units = c("SI", "Eng")
)
```

## Arguments

- Q
flow rate [\(m^3 s^{-1}\) or \(ft^3 s^{-1}\)]

- b
bottom width [\(m\) or \(ft\)]

- m
side slope (H:1) [unitless]

- y
depth of flow [\(m\) or \(ft\)] (optional)

- scale
multiplier (of yc) for axis scales (default is 3)

- units
character vector that contains the system of units [options are

`SI`

for International System of Units and`Eng`

for English (US customary) units.

## Details

Specific Energy, E, is the energy, expressed as a head (i.e., the mechanical energy per unit weight of the water, with units of length) relative to the channel bottom. It is calculated as: $$E = y+\alpha\frac{Q^{2}}{2g\,A^{2}} = y+\alpha\frac{V^{2}}{2g}$$ where \(y\) is flow depth, \(A\) is the cross-sectional flow area, \({V}=\frac{Q}{A}\), and and \(\alpha\) is a kinetic energy correction factor to account for non-uniform velocities across the cross-section; \(\alpha=1.0\) in this function (as is commonly assumed).