# Horizontal open channel flow -- Hydraulic jump calculation

1. Jan 27, 2016

### JochemGrietens

Dear Fellow Engineers

I'm having an issues with my calculations. This case concerns a open channel flow that start off being supercritical on the left and turns into subcritical flow after a hydraulic jump.

Given:
Volume flow rate Q = 0.16m^3/s
Width of the channel b = 1m
Resulting fluidheight at the left h1 = +/-6cm.

The channel slope = 0. The channel is perfectly horizontal
Mannings coefficient : 0.012

Question : Distance from the left part untill the hydraulic jump occurs. L = ?

I integrated the backwater function:
i = 0 because of slope being zero

In the figure below the X axis denotes the distance from the left to the right of the channel. the Y-axis shows the height of the fluid height (purpl/pink curve). The blew curve is the conjugate height.

I know that L can be determined from this curve but i don't know how. Can someone halp out please ?

Thank you,
Jochem Grietens

2. Feb 1, 2016