Question
Notch is a device used for measuring:
The correct answer is
Rate of flow through small channels
Understanding Flow Measurement with a Notch
A notch is a hydraulic device commonly used for measuring the rate of flow of liquids, particularly water, in small channels or tanks. It's essentially an opening in the side of a tank or channel that allows water to flow out. By measuring the height of the water level above the bottom of the notch (called the crest), the discharge or rate of flow through the notch can be calculated using specific formulas that depend on the shape of the notch (e.g., rectangular notch, triangular notch, trapezoidal notch). Here's why a notch is used for measuring flow rate:- Principle of Operation: A notch works based on the principle that the flow rate through it is directly related to the height of the liquid above the crest of the notch. As the water level rises, the flow rate increases.
- Application: Notches are typically installed at the end of a channel or the side of a tank to measure the volume of water flowing out per unit time. This makes them suitable for measuring flow in open channels or streams.
- Measurement Target: The primary measurement obtained using a notch is the volumetric flow rate (often denoted as Q), which represents the volume of fluid passing through the notch per unit time (e.g., cubic meters per second or liters per second). It does not directly measure velocity.
- Option 1: Velocity through small channels - Notches measure the rate of flow (discharge), not the velocity directly. Velocity is a different parameter, though related to flow rate and cross-sectional area.
- Option 2: Rate of flow through pipes - Notches are designed for open channels or tanks where there is a free liquid surface. They are not used for measuring flow rate in closed pipes, which typically use devices like Venturi meters, orifice plates, or flow meters based on pressure difference or other principles.
- Option 3: Rate of flow through small channels - This aligns perfectly with the function of a notch. Notches are standard devices for measuring the discharge in small to medium-sized open channels.
- Option 4: Velocity through pipes - Similar to Option 1 and 2, notches measure rate of flow, not velocity, and are used in channels, not pipes.
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Important Questions from Open Channel Flow
- 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
- 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)
- 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). A Hydraulic Jump is said to be Oscillating Jump if its Froude number is ________.
The Francis formula for the discharge over cippoletti weir is
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