This Thesis presents research into the hydraulic characteristics of flow in open channels of complex cross-section, with specific attention to the region of interaction located between the main channel and flood plain. The scope of research includes two main components: a series of detailed laboratory investigations; and the development and verification of a depth averaged two-dimensional mathematical model.
The primary objective of laboratory experiments was the acquisition of high quality data covering a well defined and controlled range of hydraulic parameters. In support of this objective, special attention is given to the comprehensive presentation of data in a format amenable to accurate assimilation by other researchers. Detailed presentations include data tabulations in both printed and computer readable (magnetic disk) formats, and graphical plots.
Laboratory experiments were undertaken in open compound channels of asymmetrical section, under conditions of uniform flow. Two channel configurations were examined: a rectangular compound channel; and a trapezoidal compound channel (sloping bed between main channel and flood plain). Wide channel geometries were selected for both channel configurations so as to support the development of near two-dimensional flow conditions adjacent both sides of the interaction region. Experimental measurements were taken over wide ranges of discharge and flood plain roughness conditions. A constant bed slope was maintained throughout. Principal measurements from each experimental run comprised high resolution boundary shear stress and velocity field distributions.
The object of theoretical investigations was the development of a mathematical model for the prediction of two-dimensional open channel hydraulic characteristics in a manner suited to the requirements of practical engineering application. The resulting model (GENFL02D) is based around an analytical solution of the depth averaged Navier-Stokes equation, in conjunction with a turbulence model using Prandtl's mixing length theory. The model may be applied to situations of known geometry and boundary roughness (using true two-dimensional roughness values) without calibration, end is shown to be well suited to both laboratory and field application. Fundamental model assumptions are that flow is straight uniform and that the influence of secondary flow is small.
Ancillary investigation items include: verification of the Preston tube for measurement of boundary shear stress; development of an alternative boundary shear :;tress measurement probe (the RPT); development of a computer based Automatic Control And Data Acquisition System (ACDAS) for probe positioning and data logging application; development of a general resistance transition function for application to artificial strip roughness; derivation of two-dimensional roughness calibration values for artificial strip roughness elements in conjunction with the development of an improved side-wall correction technique; and measurement and correction for non-hydrostatic pressure field distributions.