Author(s): Breac Macleod; Alan Ervine
Linked Author(s):
Keywords: Meandering compound channel; Flow regions; F*; Relative flow depth
Abstract: The EPSRC Series B extension programme (1993-1996) was commissioned to investigate the influence of 11 geomorphic and roughness parameters on flow behaviour in meandering compound channels. The programme collaborators were drawn from researchers at Aberdeen, Bristol and Glasgow Universities. Each institution tested between 3 and 5 parameters which were selected so that enough data was gathered over the 3 year programme period to demonstrate the influence of all 11 parameters. Fifty physical models were finally built and tested. Small scale models of the basic Wallingford configuration at a ratio of 1 in 6 were used. parameter of scale. It was essential to be able to explicitly relate the flow results from the small scale Series B extension models to those produced in Wallingford during the Series B programme (1989-1992). The Series B tests produced the most reliable meandering compound channel flow results to date and were therefore ideal to use as benchmarking data. The Series B extension team proposed that a reliable semiphysical, semi-empirical method for predicting the discharge capacity of meandering compound channels could be developed by cross-referencing both sets of data. This paper presents the authors’findings with regard to the influence of scale. used to separate the influence of bed friction resistance from that of layer interaction. The authors demonstrated that the effect of scale on bed friction could be adequately described by reference to standard resistance formulations. Thus the use of F*enabled the layer interaction mechanisms (head loss sources) corresponding to the relative flow states in the main channel and flood plain flows to be identified for different scale models over a full range of flow depths. This new approach represents a departure from the standard procedure in which meandering compound channel flow is analysed by determining how general flow parameters such as discharge or total flow resistance (often measured using a composite Manning’s‘n’or Darcy‘f’value) correspond to relative depth. These standard procedures tend to obscure the explicit influence of layer interaction and can therefore be misleading.
Year: 1999