# Weir nappe trajectory equation

Weirs are a familiar structure in hydraulic engineering, for they are applied to a wide variety of barrages, bottom drops, spillways, etc. Movable weirs form a large group of hydraulic structures characterized by the fad that, under the action of the differential head between headwater and tailwater, the discharge is passed under the structure through a variable cross-section, the magnitude of which depends on the gate opening. Szesztay It should be noted that dimensional homogeneity of Equations 2. Plank planed with great care, accurately jointed; surface finished with neat cement mortar. These can also be applied in designing the tailwater apron as follows: a The distance between the downstream edge of the weir crest and the cross-section "" of the tailwater apron can be estimated by rearranging Equation 4. Sketch of a short pipe-line for calculating manometric and suction head of pumps Figure 5. In cross-section "" the actual velocity v 2is less than the critical one, so the flow is tranquil. The first step is the calculation of the necessary gate opening, e. Classification of weirs with respect to flow over the weir; free overfall with satisfactory ventilated free jet see Fig. By further increasing discharge the structure will be submerged and it will function as a short pipeline with a favourable "bell mouth" entrance.

• Chapter 3. Hydraulic Aspects in Designing Aquaculture Systems
• Sharp Crested Weirs

• Video: Weir nappe trajectory equation Nappe (hydraulics)

lic calculation of the shape of the compact part of a nappe. the weir (without crest) flow approach (Rouse, ), the free- The trajectory of a free overfall.

Download Citation on ResearchGate | Estimating Trajectory of Free Overfall The equation of the free-flow nappe over the weir is described by a parabolic. Definition sketch of reference weir used in the nappe-fitting method.

. discharge coefficient, C, can be selected with cate that the ratio of weir height to head is .

## Chapter 3. Hydraulic Aspects in Designing Aquaculture Systems

on the weir is referenced to the highest point on governs the trajectory that the.
Following the flow direction Figure 11 the headwater depth, D, is large while velocity, v, is small. The usual relationship can be applied for calculating discharge but 2 p R is substituted for b.

The values of roughness coefficient, n, must be substituted according to Table 6. Outflow under pressure Figure In the gate opening, e, and afterwards in the contracted cross-section "" the water depth, e e, is low and the velocity, v ois much above the critical velocity between shooting and tranquil flowor generally.

As is known, the flow in open channels may be classified according to variation with respect to both location and time. The hydraulic structure which protects against this is called the tailwater apron.

 CHOSTAKOVITCH VALSE 2 PUBLIX The second most important part of head loss consists of the sum of local head losses caused by changes in direction, changes in diameter and pipe fittings such as tap, valve, etc.That means the water depth, h 1and the mean velocity, v 1at the cross-section are interrelated by the equation 4. The main part of the head loss is due to friction, the resistance coefficient of which is: 1. The flow between cross-sections "" and "", respectively, is shooting and while the depth is increasing from e e to D 1the velocity is decreasing from v 0 to v 1and in cross-section "" the actual velocity is more than the critical one, viz. As an example see Figure 4, where as well as the manometric head of the pump, the suction head can also be calculated.
Keywords: round-crested weir; flow rate; discharge coefficient; body shape weir is characterized by having no effect on a free-falling nappe and a.

the water flow path, the first rectangular channel, which was m long. In Equations () and () the only remaining problem is the dimensionless discharge The trajectory of the nappe after springing clear of the weir crest is. This technical note presents the correct and incorrect jet trajectory equations, quantifies the. the top surface of the nappe at a free overfall.

. weir crest length.
The cross-section "" is then followed by shooring flow Figure 9undulating hydraulic jump Figure 10 or perfect hydraulic jump with surface roller Figure Then a hydraulic jump follows, with a sudden variation in both water depth increase and velocity decrease. Figure 1.

Video: Weir nappe trajectory equation Flow over weirs

The relationship between overfalling discharge and hydraulic characteristics is the same but the discharge coefficient depends, besides the characteristics of M, a and h, on the type, the material and the construction method of the weir, and varies from 0. At the downstream edge of a broad crested weir the water depth is critical.

The limit of oblique weirs Figure 16b is the side weir of Figure 22, the crest of which is parallel to the main flow direction.

According to this theorem the resultant of the outside hydraulic forces has to be balanced by the change of momentum.

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Then a hydraulic jump follows, with a sudden variation in both water depth increase and velocity decrease.

## Sharp Crested Weirs

Figure 1. Free outflow followed by a perfect hydraulic jump with surface roller in the tailwater This means the most important geometric characteristics of the cross-section, viz. Figure 6. Equation 3.