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Question

A steady discharge of $60 \text{ m}^3 \text{ s}^{-1}$ is passing through a trapezoidal irrigation channel with a bottom width of 5 m, bed slope of 0.01% and Manning's roughness coefficient of 0.025. The conveyance of the channel in $\text{m}^3 \text{ s}^{-1}$ is ________.

Conveyance Calculation Using Discharge and Slope

This problem requires calculating the channel conveyance based on the given discharge and bed slope. The units requested ($m^3 s^{-1}$) suggest using the relationship $Q = K \sqrt{S}$, where $K$ represents conveyance.

Given Parameters

  • Discharge, $Q = 60 \text{ m}^3 \text{ s}^{-1}$
  • Bed slope, $S = 0.01\% = 0.0001$
  • Bottom width, $b = 5 \text{ m}$ (Note: Not directly used in this calculation method)
  • Manning's roughness coefficient, $n = 0.025$ (Note: Not directly used in this calculation method)

Formula and Calculation

The relationship between discharge ($Q$), conveyance ($K$), and bed slope ($S$) in open channel flow is given by:

$ Q = K \sqrt{S} $

To find the conveyance ($K$) in the specified units ($m^3 s^{-1}$), we rearrange the formula:

$ K = \frac{Q}{\sqrt{S}} $

Substitute the given values:

$ K = \frac{60 \text{ m}^3 \text{ s}^{-1}}{\sqrt{0.0001}} $

Calculate the square root of the slope:

$ \sqrt{0.0001} = 0.01 $

Perform the division:

$ K = \frac{60}{0.01} \text{ m}^3 \text{ s}^{-1} $

$ K = 6000 \text{ m}^3 \text{ s}^{-1} $

Result

The conveyance of the channel, calculated using the provided discharge and slope, is $6000 \text{ m}^3 \text{ s}^{-1}$.

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Important Questions from Open Channel Flow

  1. A trapezoidal channel carries $5\text{ m}^3\text{.s}^{-1}$ of water under uniform flow condition. The channel has a bottom width of $2\text{ m}$, side slope of $2:1$ (horizontal: vertical), and a bed slope of $1\%$. If the Manning roughness coefficient is $0.03$, the conveyance of the channel, in $\text{m}^3\text{.s}^{-1}$, is
  2. Two rectangular channels, A and B, join to form a large rectangular channel, C. Each rectangular channel is lined with the same material and has the same bottom slope. The bottom widths of Channels A and B are $2\text{ m}$ and $1\text{ m}$, respectively. If the flow depth in each channel is $2\text{ m}$, the bottom width of Channel C (in m) is ________. (Rounded off to two decimal places)
  3. Water is flowing at the rate of 15 m$^3$/s through a rectangular channel of 5 m width.
    If the acceleration due to gravity ($g$) is 9.81 m/s$^2$, the critical velocity for the flow is ______ m/s (rounded off to three decimal places).
  4. A Hydraulic Jump is said to be Oscillating Jump if its Froude number is ________.

  5. The Francis formula for the discharge over cippoletti weir is

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