AI SearchA study of compound weirs
Call Number: AIT Thesis no.WA-87-1 Material type:
TextSeries: Asian Institute of Technology. Thesis ; no. WA-87-1Publication details: Bangkok : Asian Institute of Technology, 1987Description: 135 pSubject(s): Online resources: Dissertation note: Thesis (M.Eng.) - Asian Institute of Technology, 1987 Summary: Parshall flume, standard rectangular weir, and 90° V-notch weir are commonly used as flow measurement devices. All of them show good applicability within a limited range of discharge to be measured. However, in a small watershed area when the rainfall is not uniformly distributed, heavy rainfall in wet season and the low flow during the dry season, ensures considerable fluctuation of the discharges. The existing devices are not appropriate for the flow measurement under such conditions. In such areas, the compound weir is needed for this purpose . The necessity of having accurate information on the performance characteristics of compound weirs has focused attention to study its behaviour under free overfall conditions. A theory is outlined which helps to explain the flow over compound weirs, whose application is shown to be reasonably justified in the present context. Experiments on twelve weirs of three sets are shown to confirm the trends predicted by the theory. A discharge equation of the form Q = K.Hn is formulated, where Q is discharge, K is dimensional constant of proportionality, H is measured head, and n is hydraulic exponent . Such a definitive and unique relationship offers a practical basis for the measurement of discharge in open channels. An accurate method for determining the discharge coefficients is presented and the coefficients are determined for each of the compound weirs. The limits of validity of the results are investigated. The summary of the results is presented in graphic and tabular forms. Finally, sensitivity analysis, by varying the discharge coefficients has been carried out to help identifying the potential importance of these parameters. A comparison of the theoretically determined solution with observations indicates a fair agreement, and allows a simple prediction of all pertinent flow characteristics.
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A thesis study submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology
Thesis (M.Eng.) - Asian Institute of Technology, 1987
Parshall flume, standard rectangular weir, and 90° V-notch weir are commonly used as flow measurement devices. All of them show good applicability within a limited range of discharge to be measured. However, in a small watershed area when the rainfall is not uniformly distributed, heavy rainfall in wet season and the low flow during the dry season, ensures considerable fluctuation of the discharges. The existing devices are not appropriate for the flow measurement under such conditions. In such areas, the compound weir is needed for this purpose . The necessity of having accurate information on the performance characteristics of compound weirs has focused attention to study its behaviour under free overfall conditions. A theory is outlined which helps to explain the flow over compound weirs, whose application is shown to be reasonably justified in the present context. Experiments on twelve weirs of three sets are shown to confirm the trends predicted by the theory. A discharge equation of the form Q = K.Hn is formulated, where Q is discharge, K is dimensional constant of proportionality, H is measured head, and n is hydraulic exponent . Such a definitive and unique relationship offers a practical basis for the measurement of discharge in open channels. An accurate method for determining the discharge coefficients is presented and the coefficients are determined for each of the compound weirs. The limits of validity of the results are investigated. The summary of the results is presented in graphic and tabular forms. Finally, sensitivity analysis, by varying the discharge coefficients has been carried out to help identifying the potential importance of these parameters. A comparison of the theoretically determined solution with observations indicates a fair agreement, and allows a simple prediction of all pertinent flow characteristics.
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