Flow in Open Channels

​Flow in Open Channel

Uniform Flow in Trapezoidal Channel​

Elective/ ME 400, 1S 2022-2023

In general, the analysis of channel flow is more difficult than that of pipe flow as there are many more variables. Some approximate analyses are possible.

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Natural​ channels (mainly rivers) are the most variable while the man-made channels are more regular and thus hydrological theories are more accurate.

Elective/ ME 400| S1S 2022-2023

Flow in Open Channel

Elective/ ME 400| S1S 2022-2023

Flow in Open Channel

Elective/ ME 400| S1S 2022-2023

Flow in Open Channel

Elective/ ME 400| S1S 2022-2023

Flow in Open Channel

Elective/ ME 400| S1S 2022-2023

Flow in Open Channel

​Unit Tractive Force

Elective/ ME 400| S1S 2022-2023

Flow in Open Channel

​Chezy's Formula

Elective/ ME 400| S1S 2022-2023

Flow in Open Channel

​Kutter's Formula

Elective/ ME 400| S1S 2022-2023

Flow in Open Channel

​Unit Tractive Force

Elective/ ME 400| S1S 2022-2023

Flow in Open Channel

​Unit Tractive Force

Elective/ ME 400| S1S 2022-2023

Flow in Open Channel

​Unit Tractive Force

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d > d_c​ (subcritical)

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d = d_c​ (critical)

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d < d_c​ (supercritical)

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Elective/ ME 400| S1S 2022-2023

Flow in Open Channel

​Type of flow:

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d > d_c​ (subcritical)

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d = d_c​ (critical)

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d < d_c​ (super critical)

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Elective/ ME 400| S1S 2022-2023

Flow in Open Channel

​Type of flow: (Depth)

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V < V_c​ (subcritical)

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V = V_c​ (critical)

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V > V_c​ (super critical)

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Elective/ ME 400| S1S 2022-2023

Flow in Open Channel

​Type of flow: (Velocity)

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S_o < S_c​ (subcritical)

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S_o = S_c​ (critical)

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S_o > S_c​ (super critical)

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Elective/ ME 400| S1S 2022-2023

Flow in Open Channel

​Type of flow: (Slope)

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F < 1.0​ (subcritical)

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F = 1.0​ (critical)

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F > 1.0​ (super critical)

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Elective/ ME 400| S1S 2022-2023

Flow in Open Channel

​Type of flow: (Froude No.)

​A trapezoidal channel has a bottom width of 6 m. and side slope of 2 horizontal to 1 vertical when the depth of flow is 1.2 m, the flow is 20.40 m³/s.

1. Compute the specific energy.

2. Compute the slope of the channel if n=0.014.

3. Compute the average shearing stress at the boundary.​

​Problem #1

​Problem #1

​Problem #1

​The bottom width of a trapezoidal canal is 2.5 m. and its sides are both inclined at 60 deg. with the horizontal. Water flows at a depth pf 3 m. The slope is 0.0008 and n = 0.03.

1. Find the hydraulic radius.

2. Find the value of Kutters coefficient C.

3. Find the discharge using Chezys Formula.​

​Problem #2

​Problem #2

​Problem #2

​A trapezoidal channel has a bottom width of 6 m. and side slopes of 2 horizontal to 1 vertical. When the depth of water is 1.0 m., the flow is 10 m³/s.

1. What is the specific energy?

2. What is the critical depth?

3. What type of flow is this?​

​Problem #3

​Problem #3

​Problem #3

​Problem #3

​3. Type of flow:

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  d = 1.0

​d_c​ = 0.611

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d > d_c​ ; therefore the flow is subcritical

​Water flows in the symmetrical trapezoidal channel lined with asphalt has a base width of 4.8 m. and side slope of 3 horizontal to 1 vertical. It has a depth of flow of 1.36 m. The channel drops 0.1 m. vertically every 100 m. of length. Assuming coefficient of roughness n = 0.015.

1. Determine the velocity of flow.

2. Determine the Froude number.

3. Determine the type of flow.​

​Quiz...

​Water flows in the symmetrical trapezoidal channel lined with asphalt has a base width of 4.8 m. and side slope of 3 horizontal to 1 vertical. It has a depth of flow of 1.36 m. The channel drops 0.1 m. vertically every 100 m. of length. Assuming coefficient of roughness n = 0.015.

1. Determine the velocity of flow.

2. Determine the Froude number.

3. Determine the type of flow.​

​Problem #4

​Problem #4

​Problem #4

​3. Type of flow:

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F < 1 ; therefore the flow is subcritical