Now showing 1 - 2 of 2
  • Publication
    Discharge assessment in mobile-bed compound meandering channels
    (Institution of Civil Engineers, 2003-12-01) ; ; ;
    Many discharge prediction methods have been developed for compound meandering channels. Most of these methods have been found to produce reasonable results for fixed-bed channels, but the effects of the presence of a mobile main channel bed on discharge assessment have yet to be assessed. Sediment movement increases the complexity of experiments by facilitating the creation of bedforms, which alter flow resistance. The shape characteristics of these bedforms and their associated roughness are known to depend on channel stage and geometry, and to vary with flow conditions. This paper seeks to assess the performance of six discharge assessment methods using the Phase C mobile-bed meandering UK Flood Channel Facility (FCF) overbank flow data. The results show that the accuracy of the different methods depends heavily on the boundary roughness, and the James and Wark (1992) method performed most consistently for the range of floodplain configurations tested. A modification to this method is also presented that is shown to improve the accuracy of the predicted discharges.
    Scopus© Citations 2  569
  • Publication
    Stage–discharge prediction in straight compound channels using 3D numerical models
    (Institution of Civil Engineers, 2012-06) ; ;
    An improved approach for applying three-dimensional (3D) computational fluid dynamics (CFD) models to estimate uniform flow stage–discharge relationships and velocity distributions in straight compound channels is presented. Commonly used modelling approaches tend to be over-specified. For a given flow and water level, desired results are obtained through calibration of resistance coefficients that can be artificially high and vary with changing flow conditions. Furthermore, the momentum interaction at the main channel–floodplain interface is sometimes ignored or is accounted for using a constant eddy viscosity. This potentially results in an overestimation of conveyance capacity in compound channels. The proposed approach represents an advance on these methods and uses a 3D CFD model with k– turbulence closure in a predictive capacity where a flow together with physically realistic resistance coefficients are specified. Downstream water levels are then iteratively adjusted until uniform flow conditions are established in the channel. The approach is validated against benchmark experimental data obtained from the largescale UK Flood Channel Facility and is compared with predictions from divided channel methods.
      1231Scopus© Citations 9