The upper surface of a weir over which water flows is known as
sill
Understanding the Weir and its Upper Surface
A weir is a barrier built across a river or stream to raise the water level or to measure the flow rate. Weirs are commonly used in hydraulics and water management.
Let's look at the different parts of a weir and the terms used to describe them.
Identifying the Upper Surface of a Weir
The question asks for the name of the upper surface of a weir over which water flows. In hydraulic terminology, specific names are given to different parts of the water flow and the structure itself.
Consider the following terms:
- Vein: This term usually refers to a stream or flow within a larger body of water, not a part of the weir structure.
- Nappe: The nappe is the sheet or stream of water that flows over the crest of a weir. It is the flowing water itself, not the physical surface of the weir.
- Sill: The sill is the technical term for the crest or the top edge of a weir over which the water flows. It is the upper surface of the weir structure.
- Weir top: While this is a descriptive term, 'sill' is the precise technical term used in hydraulics for the upper surface of the weir where overflow occurs.
Analyzing the Options
Based on the definitions:
- Vein is not a part of the weir structure.
- Nappe is the water flowing over the weir, not the weir surface itself.
- Sill is the correct technical term for the upper surface or crest of the weir.
- Weir top is a general description, but sill is the specific term.
Therefore, the upper surface of a weir over which water flows is known as the sill.
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
