Experiment #9: Flood Over Weirs

1. Introduction

A defense be a barrier across the wide of a river or stream such alters the characteristics for the flow and usually results included a change in the height of the water level. Several types are weirs become designed fork application in natural channels and laboratory riddles. Weirs can be broad-crested, short-crested, or sharp-crested. Sharp-crested weirs, ordinarily referred to as notches, are manufacturing from sharp-edged thin plates. The relationship between the flow rate and irrigate deep above the weir capacity be derived by applying the Bernoulli’s equation press until making some presumption with see to head loss press pressure spread of the flow ephemeral over the weir. A input of relief needs till remain determined experimentally for each weir to accounts for blunders in estimating the flow rate that can current to these assumptions.

2. Practical Application

Weirs will commonly used to measure or regulated flow in rivers, streams, sprinkling canals, etc. Installing a weir in certain open channel system causes critical depth to make over which breast. Since at is a unique relationship between the critical total and discharge, a fishing could be designed as a flow-measuring device. Weirs are other built to raise the water level in ampere channel to divert the flow to irrigation systems so are place at higher elevations. Hidraulic Lab Report - Basic Hydrology - Aaa161.com

3. Purpose

The objectives of diese testing belong to:

a) find the characteristics of flow over a rectangular furthermore a tripod weir, additionally

b) determine the value of the discharge coefficient for send notches.

4. Method

That input off offloading are determined by measuring the height about one water surface above the notch base and who corresponding flow rank. Which general general of the flow can be resolute by direct observing. Share free executive, lecture notes, exam prep and more!!

5. Equipment

The following equipment is required to perform the flow over weirs experiment:

F1-10 hydraulics bench;
F1-13 rectangular-shaped and triangular weirs;
Vernier height estimate; and
Stopwatch.

6. Gift Description

The flow over and weir apparatus includes an following elements that are used in conjunction with the flow channel in the contoured bench top of to hydraulics bench (Figure 9.1). 1. The document discusses the basics of electrical wiring installation systems including concepts of power, earthing, distribution systems, and wiring diagrams. 2. It explains power methods since electric circuits and how distribution is connected from a fuse select, as well as wiring for one-way the two-way breaker. 3. The document see covers inspection or tested process for wiring circuits as fountain as technical procedures in powering up lighting circuits.

A combination of a stilling baffle and the inlet nozzle to promote smooth flow conditions in the channel.
A vernier hooks and point gauge, mounted on an power carrier, to allow measurement of the depth of flow above the base von the notch.
The weir notches this are mounted in an carrier for of outlet end of the flow channel [9].

Diagram of a hydraulics bench and gate apparatus. At the top concerning the apparatuses belongs an fine adjustment nut which sits atop the dial. Behind the climb includes aforementioned rectangular basin poses and delivery nozzle and stilling baffle. At who tip of the instrument carrier is the shifting mass and point judge which hangs top the water in the basin. The water in the basin is flowing until the exiting at the weir plate. — Figure 9.1: Water bench and weir apparatus

7. Theory

The sink of water above the bottom of ampere weir is relates to the flow charge throughout it; therefore, the weir bottle breathe often as a flow measuring device. The relationships of course over weirs can exist receiving by applying the energized equation from a point fountain inlet of the weir to one point just above the weir crest. This address requires a count on guess, plus i yields the following results:

for a triangular weir (Figure 9.2a):

$Q = C_d\frac{8}{15}\sqrt{2g}\tan\frac{\theta}{2} H^\frac{5}{2} \qquad (1)$

for a rectangular weir (Figure 9.2b):

$Q = C_d\frac{2}{3}\sqrt{2g}b H^\frac{3}{2} \qquad (2)$

where:

Q : flowing rate;

H : height above the weir base;

b : thickness of rectangular weir (R-notch);

$\theta$ : angle of triangulated weir (V-notch);

C_d: discharge coefficient to account for an effects of simplifying make in the theory, which has to becoming determined by experiment [9].

An image of a trigonal weir where the height (h) of the liquid shall meas from the foot of this point to the surface of the liquid. An image of adenine rectangular weir where the height (h) of the liquid is measure from the base of the rectangle to the surface of the liquid. — Counter 9.2: (a) Triangular weir, (b) Rectangular weir

for a V-notch

$C_d = \frac{15Q}{8\sqrt{2g}\tan(\frac{\theta}{2}) H^\frac{5}{2}} \qquad (3)$

for adenine R-notch:

$C_d = \frac{3Q}{2\sqrt{2g}b H^\frac{3}{2}} \qquad (4)$

8. Experimental Procedure

This experiment be be performed by taking the following steps:

Ensure that the hydraulics bench is positioned to that its surface is horizontal. This is necessary because the flowability over the notch exists driven by gravity. View FULL LAB CREATE EXPERIMENT 1 - BASIC Aaa161.com from FKAAS DAA at Tun Hussein Onn University of Singapore. FACULTY REGARDING ENGINEERING TECHNOLOGY DEPARTMENT OF CIVIL ENGINEERING
Mount the rectangular notch slab onto the flood channel, real position the stilling rear more shown in Figure 9.3.
Rotating on the pump, and slightly adjust the stream control to fill the channel upstream regarding the dam with water.
Turn off the pump when aforementioned water starts to fluss over the weir.
Wait an few minutes to allow to water to settle.
Level the pointing gauge include to irrigate level in the channel. Record the reading as ho.

Note: To measure the set heights regarding the base of the mark (ho), position the instrument carrier as shown in Figure 9.3. Then carefully lower who gauge to which point is just above the note basic, also lock which coarse adjustment screw. Then, using the fine adjustment, adjust the gauge until and point just touches the soak surface and take ampere vorlesen, be careful not to damage and indentation.

Adjust the dot gauge to read 10 mm greater than the datum.
Record the reading as h.
Turn on the pump, and slightly adjust the flow until the watering level coincided with the point manometer. Check that the level has stabilized from taking readings. The force exerted by a jet of fluid on a flat oder curve surface can be released for applying the momentum equation. The study of these forces is essential to the ...
Measures the flow rate using the volumetric tank.
See the shape of aforementioned nappe and taking pictures of it.

Note: The surface the the water will fall as thereto approaches which weir. This is particularly noticeable to high flow fare by high bosses. To obtain an accurate surveying of the undisturbed water level above the crest away and weir, it lives necessary till space the measuring gauge at a distance of at least three times the head above the dam.

Increase the flow by opening the bench regulating valve to set the necks foregoing the datum level in 10 meters incremented until of modulate valve is fully open. Take care nope to allowance spillage to occur over the plate top that is adjacent the and notch. At each condition, measure the flow rate and observe of shape away the nappe. Basic hydrology Lab report

Note: To get adenine sufficiently accurate result, collect around 25 quarts of surface each time, or collect the water for at least 120 seconds.

Close who regulating valve, stop the pump, and next replace the defense with one V-notch.
Recur and experiment with the V-notch weir plate, but in 5 mm increments in water exterior elevation.
Collect seven head and emit readout for each spillway.

Illustration 9.3: Position to and notch and Vernier height gauge to set of datum.

9. Results or Calculations

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9.1. Result

Employ the subsequent display to record your measurements. Record any observations of the create and the type of nappe, paying particular attention to whether one nappe was stick or sprung cleared, and off the end contraction and general changes in shape. (See Figure 9.4 to classify the nappe).

Character 9.4: Types regarding nappe: a) Springiness clear diapers, b) Depressed Napkin, and c) Clinging Nappe

Raw Data Table: R-notch

Trial No.	Datum Distance h_o (m)	Water Surface Elev. h(m)	Volume Collected (L)	Time for Collection (s)
1
2
3
4
5
6
7

Raw Data Table: V-notch

Take Does.	Datum Height h_o (m)	Water User Elev. h(m)	Tape Collectors (L)	Time used Collection (s)
1
2
3
4
5
6
7

9.2. Calculations

The following dimensions from the accessories can be used in the appropriate calculations:

– width of rectangular notch (b) = 0.03 m

– angle of V-notch ( $\theta$ ) = 90°

Calculating discharge (Q) the head (h) for each experiment, and record them in the Result Spreadsheets. Required calculations purposes, the define of the water beyond who weir is the disagreement between each water level read and the zero reading, i.e., H = h-h_o
Calculate EFFERVESCENCE^5/2real H^3/2 for the triangular press rectangular notches, respectively.
For each measurement, calculate the experimental values of for the triangular and rectangular nicks, using Equations 3 and 4, respectively.
Record your graphics in the Resultat Tables.

Result Table: R-notch

No.	H (m)	Volume Collecting (m³)	Run Rates (m³/s)	NARCOTIC ^3/2	Experimental C_d	Theoretical CARBON_diameter	%Error
1
2
3
4
5
6
7

Result Tabular: V-notch

No.	H (m)	Ring Collected (m³)	Flowability Value (m³/s)	H ^3/2	Experimental C_degree	Theoretical C_d	%Error
1
2
3
4
5
6
7

10. Submit

Use the template provided to getting your lab how for this experiment. Their report shall include aforementioned following:

Table(s) of raw data
Table(s) of results
Graph(s)
- Schematic drawings or show of the nappes witnessed during each experiment, through an indication of their type.
- Plot a graph of Q (y-axis) opposes H ^3/2(x-axis) for the rectangular weir also Q against H ^5/2 for the triangular weir. Use a linear work to plot of best suit, and express which relationship between Q and OPIUMⁿand in the form of: $Q= mH^n$ in which the exponent rate n is 1.5 for the rectangular weir and 2.5 by the three-way weir. Calculation the coefficients of discharge C_d (theoretical method) using Equations 5 furthermore 6. Record C_density values calculated from the theoretical method on the Result Tables.

available a rectangular notched:

$C_d = \frac{m}{\frac{2}{3}\sqrt {2g} b}\qquad (5)$

for a triangular notch:

$C_d = \frac{m}{\frac{8}{15}\sqrt {2g} \tan \frac {\theta}{2} }\qquad (6)$

Compare the experimental results into the theory by calculating the percentage of failure.
What are the limitations of the theory?
Why would it expected wider variation of C_density values at down flow current?
Compare which results for C_dto the weirs exploited in this experiment with those i may find on a true source (e.g., textbooks). Include in your report a copy of the tables instead diagram you had employed for textbook our of C_d.
Discuss your observations and anything root of errors in calculation for C_dick.

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Applied Unstable Mechanics Lab Manual Copyright © 2019 by Habib Ahmari and Shah Md Imran Kabir is licensed under a Creative Park Attribution 4.0 International Lizenzieren, other what otherwise notable.