The water which is approaching the weir possesses a certain velocity known as the velocity of approach. If the velocity of approach is also considered, then, q = 1.84 [l – 0.1 n (H + ha)] [(H + ha)3/2 – ha 3/2]. The head ha is called the head due to the velocity of approach. difference Notches will be small in size but weir will be bigger First, let us understand what is fluid couplin... We were discussing thermodynamic state, path,process and cycles in our previous post. In this case the water level on the downstream side also is above the crest of the weir. This site uses Akismet to reduce spam. At the end of our discussion we will understand the differences between both of them. Let v be the uniform velocity of flow over the weir. A notch is generally meant to measure the flow of water from a tank. Now to have better clarity on notches and weirs, we should understand differences between them. As the water flows over the weir, it reaches a uniform depth of flow h, over the crest. Fluid Mechanics, Water, Flow, Measurement, Notches, Classification of Notches and Weirs. We hav... Hello once again We have discussed in previous post about  causes of hydraulic system overheating  , cost of hydraulic oil leaks  and &q... in the subject of fluid mechanics in our recent termed as sill or crest. According to Francis each lateral contraction (also called end contraction) is equal to 0.1 H. If the actual length of the weir is l, then the effective length of the weir will be (I – 0.2 H). They can be classified into sharp crested and broad-crested weirs based on the sharpness of the crest. Weirs may also be classified into suppressed weirs and weirs with lateral contraction. Let it be required to find the time taken for the head of water over the weir to fall from a value H1 to a value H2. Prohibited Content 3. in size. Hence head measurement can be done more accurately over the triangular notch than over the rectangular notch. structure which will be located in an open channel over which flow will take across the river or large canal for storing water on upstream side. Bottom edge of notch over which liquid flows will be Fig. If the sheet of water springs free as it leaves the crest, the weir is called a sharp crestel weir. According to the shape of opening, notches can be classified as, 5.2. liquid surface in the tank or channel is below the top edge of opening. The quantity H + ha is called still water head. They can be classified into waste weirs and gauging weirs based on the purpose for which they are provided. Consider the weir shown in Fig. We may first calculate the discharge ignoring the velocity of approach. Sometimes masonry structures are built on the top of the raised weir in which openings fitted with sluice gates are provided. Notches will be small in size and will be preferred Let the time taken by the sheet of water to jump across the opening be t seconds. to use for measuring the small discharge of small stream or canal. Weirs can be classified on the basis of shape of opening, on the basis shape of Crest (or Sill) and on the basis of effects of sides on the Nappe (or Vein). Huge Collection of Essays, Research Papers and Articles on Business Management shared by visitors and users like you. OUTLINE Notch Types of Notch Weir Types of weir Difference between Notch & Weir 1 2 3.

here. Let the heads on the weirs be H and h. Let discharge Q and q over them are given by –. The common shapes of weirs are, rectangular, triangular, trapezoidal, composite, parabolic and proportional. A separating weir is an arrangement provided in the case of town water supply, where it may become necessary to divert the discoloured flood water from the supply channel. Thus in an ogee weir, the solid boundary of the weir exactly coincides with the bottom surface of the nappe of the sharp crested weir under the designed head. (ii) When the discharge rate is small a triangular notch provides a greater head than the rectangular notch. We were discussing the “ Elongation of uniformly tapering circular rod ” and “ Elongation of uniformly tapering rectangular rod ” and also... We will discuss here the difference between positive and non-positive displacement pump with the help of this post. These terms are, Now we can move our discussion further on the, Notch without end contraction or suppressed notch, Used to regulate discharge of small channels, Used to regulate discharge of large channels, like canals and rivers. We know for a rectangular notch of length I the discharge over the notch is given by. It is used to regulate the flow of fluid.