The rating of sluicing flumes in combination with sharp-crested and crump weirs under modular and non-modular flow conditions

Bruce, H. G. S. (2000-12)

Thesis (MEng)--University of Stellenbosch, 2000.

Thesis

ENGLISH ABSTRACT: As part of a previous WRC project, three types of sluicing flumes were developed for use in compound weirs in combination with sharp-crested and crump weirs, (Rossouw et al., 1998). These sluicing flumes have several advantages which make them ideal structures for flow measurement in South African rivers. These are a high modular limit, stable modular flow characteristics, an ability to measure a wide range of flows accurately, as well as good sediment handling characteristics. These three flumes have been calibrated under modular or free flow conditions in combination with sharpcrested and crump weirs. There is a high degree of variability of flow in South African rivers. Flood discharges are part of this variability, and can form an important part of the mean annual runoff. Measuring weirs cannot always be built so that they do not become submerged during floods, but it is nevertheless important that flood discharges be recorded. It is therefore important that these compound weirs be calibrated for flow measurement under non-modular or submerged conditions. The purpose of the research undertaken for this WRC project is to find a method to calculate the non-modular discharge over compound weirs consisting of sluicing flumes in combination with sharp-crested and crump weirs. By analysis of existing data from the previous WRC project, as well as data from laboratory tests undertaken as part of this project, the submergence effect of sluicing flumes has been quantified. A range of configurations of sharp-crested weirs as well as crump weirs in combination with the sluicing flume have been tested. A new method has been developed to calculate the submerged discharge over these compound weirs. This method is suitably accurate, and can be recommended to the DWAF for use. The calculation procedure that must be followed in order to calculate the submerged discharge over these compound weirs becomes rather complicated due to the iterations that must be carried out. In order to clarify these procedures, flow charts are provided which set out the steps that must be followed. Calibration curves for all the combinations of compound weirs analysed in this report are also provided. These can be used to obtain estimates of the discharge in the field, and can also be used as a check on any calculations carried out. The principal goal of this project, namely that of finding a suitably accurate method to calculate the non-modular discharge over these compound weirs has therefore been achieved.

AFRIKAANSE OPSOMMING: As deel van 'n vorige Water Navorsings Kommisie (WNK) projek, is drie spoelgeute ontwikkel vir gebruik in saamgestelde meetwalle in kombinasie met skerp-kruin en Crump oorlope, (Rossouwet al., 1998). Die spoelgeute het eienskappe wat hulle gunstig maak vir vloeimeting in Suid Afrikaanse riviere. Vanhierdie eienskappe is 'n hoë modulêre limiet, stabiele modulêre vloei eienskappe, goeie sediment hanterings eienskappe en 'n vermoë om oor 'n wye bereik vloeie akkuraat te kan meet. Hierdie drie geute is in kombinasie met skerpkruin en Crump oorlope gekalibreer onder vryvloei toestande. Vloeie varieër baie in Suid Afrikaanse riviere. Vloede is deel van hierdie variasies en maak 'n belangrike deel uit van die gemiddelde jaarlikse afloop. Meetwalle kan nie altyd gebou word sodat hulle nie versuip tydens vloede nie, maar dit is nogtans belangrik dat hierdie vloeie gemeet word. Daarom is dit belangrik dat saamgestelde meetwalle gekalibreer is vir vloeimeting onder versuipte of nie-modulêre toestande. Die doel van die navorsing wat gedoen is vir hierde WNK projek was om 'n geskikte metode te ontwikkel om die nie-modulêre vloeie oor saamgestelde meetwalle, wat bestaan uit spoelgeute in kombinasie met skerpkruin en Crump oorlope, te kan bereken. Met die analise van bestaande data van die vorige WNK projek, asook data van labratoriumtoetse wat gedoen is as deel van hierdie projek, is die versuiping van spoelgeute beskryf. 'n Hele reeks skerpkruin asook crump oorlope is getoets in kombinasie met die spoelgeute. 'n Nuwe metode is ontwikkel om die nie-modulêre vloei oor hierdie saamgestelde meetstrukture te kan bereken. Hierdie metode IS akkuraat genoeg om aan die Departement van Waterwese te kan aanbeveel. Die berekingsproses wat gevolg moet word om die versuipte vloei oor die saamgestelde meetstrukture te bereken, raak ingewikkeld as gevolg van die iterasies wat uitgevoer moet word. Vloeidiagramme is opgestel wat hierdie prosedures duidelik uiteensit. Kalibrasie kurwes is ook ontwikkel vir al die kombinasies van saamgestelde meetwalle wat geanaliseer is in hierdie verslag. Hierdie kurwes kan gebruik word om skattings te maak van vloeie in die veld, maar ook om enige berekings wat gedoen is te kontroleer. Die hoofdoel van hierdie projek, naamlik om 'n geskikte metode te ontwikkel wat die nie-modulêre vloeie oor saamgestelde meetwalle akuraat kan bereken, is bereik.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/52006
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