spec_energy_trap {hydraulics} | R Documentation |
Creates a specific energy diagram for a trapezoidal channel
Description
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 [ |
b |
bottom width [ |
m |
side slope (H:1) [unitless] |
y |
depth(s) of flow (a numeric vector of length <= 2) [ |
scale |
multiplier (of yc) for axis scales (default is 3) |
units |
character vector that contains the system of units [options are
|
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).
Value
a specific energy diagram
Author(s)
Ed Maurer
Examples
# Draw a specific energy diagram for a cross-section with flow 1, width 2, side slope 3:1 (H:V)
spec_energy_trap(Q = 1.0, b = 2.0, m = 3.0, scale = 4, units = "SI")
# Draw the same specific energy diagram adding lines for depths, y = 0.5 and 0.8 m
spec_energy_trap(Q = 1.0, b = 2.0, m = 3.0, scale = 4, y = c(0.5, 0.8), units = "SI")