A hydraulic jump occurs in a 15-m wide rectangular, concrete channel. The initial (normal) depth comes from a spillway discharge of 100 m^3/s with a slope of 10%. The sequent depth is 3.00 m.
Determine the energy loss and the specific force per unit width of the channel.

Respuesta :

Answer:

The head loss = 0.1357 m

The energy loss per unit width of the channel is 3.252 m

The Specific force per unit width of the channel, [tex]M_{unit}[/tex] is 6.01 m²

Explanation:

 

Here, the slope is 10 %, therefore for every one unit traveled vertically we have 10 units traveled horizontally

Therefore when the depth is 3.00 m, we can select the initial depth as the reference = 1.00 m

We have V₁ = 100 m³/s ÷ (15×1) =  20/3 m/s

V₂ = 100 m³/s ÷ (15×3) =  20/9 m/s

[tex]y_1+\frac{V_1^2}{2\cdot g} = y_2+\frac{V_2^2}{2\cdot g} +h_L[/tex]

[tex]-h_L = y_2+\frac{V_2^2}{2\cdot g} -(y_1+\frac{V_1^2}{2\cdot g})[/tex]

[tex]-h_L = 3+\frac{\frac{20}{9} ^2}{2\cdot 9.81} -(1+\frac{\frac{20}{3} ^2}{2\cdot 9.81 })[/tex] = -0.1357

y₂ - y₁ = 2.00 m  

We have energy loss per unit width of the channel give by

[tex]E = \frac{q^{2} }{2gy^2} +y[/tex]

Where:

q = Unit discharge = Q/b = 20/3

b = Widtjh of the chammel

Therefore

[tex]E = \frac{\frac{20}{3} ^{2} }{2\times 9.81 \times 3^2} +3[/tex] = 3.252 m

The specific force per unit width of the channel is given by

[tex]M_{unit} = \frac{y^2}{2} +\frac{q^2}{g\cdot y}[/tex]

Where:

[tex]M_{unit}[/tex] = Specific force per unit width of the channel

[tex]M_{unit} = \frac{3^2}{2} +\frac{(20/3)^2}{9.81\cdot 3}[/tex]  = 6.01 m²