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Question

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

The correct answer is
$50$

Trapezoidal Channel Conveyance Calculation

This problem requires finding the conveyance factor ($K$) for a trapezoidal channel. Given the specific discharge ($Q$) and the bed slope ($S$), we can directly calculate the conveyance factor associated with this flow condition. The bottom width, side slope, and Manning's roughness coefficient are implicitly accounted for in the given discharge value for the specified slope.

Conveyance Formula for Uniform Flow

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

$Q = K \sqrt{S}$

To find the conveyance ($K$), we rearrange the formula:

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

Given Parameters

  • Discharge, $Q = 5\text{ m}^3\text{.s}^{-1}$
  • Bed Slope, $S = 1\% = 0.01$

Calculation Steps

  1. Calculate the square root of the bed slope:

    $\sqrt{S} = \sqrt{0.01} = 0.1$

  2. Substitute the values of $Q$ and $\sqrt{S}$ into the conveyance formula:

    $K = \frac{5\text{ m}^3\text{.s}^{-1}}{0.1}$

  3. Compute the final value for conveyance ($K$):

    $K = 50\text{ m}^3\text{.s}^{-1}$

Result

The calculated conveyance of the channel is $50\text{ m}^3\text{.s}^{-1}$. This matches Option D.

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Important Questions from Open Channel Flow

  1. 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)
  2. 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).
  3. A Hydraulic Jump is said to be Oscillating Jump if its Froude number is ________.

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

  5. The Cippoleti weir is a ______ weir.

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