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

[摘要] ENGLISH ABSTRACT:As part of a previous WRC project, three types of sluicing flumes were developed foruse in compound weirs in combination with sharp-crested and crump weirs, (Rossouwet al., 1998). These sluicing flumes have several advantages which make them idealstructures for flow measurement in South African rivers. These are a high modularlimit, stable modular flow characteristics, an ability to measure a wide range of flowsaccurately, as well as good sediment handling characteristics. These three flumes havebeen calibrated under modular or free flow conditions in combination with sharpcrestedand crump weirs.There is a high degree of variability of flow in South African rivers. Flood dischargesare 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 duringfloods, but it is nevertheless important that flood discharges be recorded. It istherefore important that these compound weirs be calibrated for flow measurementunder non-modular or submerged conditions.The purpose of the research undertaken for this WRC project is to find a method tocalculate the non-modular discharge over compound weirs consisting of sluicingflumes in combination with sharp-crested and crump weirs.By analysis of existing data from the previous WRC project, as well as data fromlaboratory tests undertaken as part of this project, the submergence effect of sluicingflumes has been quantified. A range of configurations of sharp-crested weirs as wellas crump weirs in combination with the sluicing flume have been tested. A newmethod has been developed to calculate the submerged discharge over thesecompound weirs. This method is suitably accurate, and can be recommended to theDWAF for use.The calculation procedure that must be followed in order to calculate the submergeddischarge over these compound weirs becomes rather complicated due to theiterations that must be carried out. In order to clarify these procedures, flow charts areprovided which set out the steps that must be followed.Calibration curves for all the combinations of compound weirs analysed in this reportare 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 tocalculate the non-modular discharge over these compound weirs has therefore beenachieved.

[发布机构] Stellenbosch University