Author(s): Heide Friedrich; Bruce W. Melville; Vladimir Nikora; Stephen E. Coleman
Keywords: Flume; Scaling; Growth; Dune; Side-wall effect
Abstract: This paper presents the results of a flume comparison study undertaken at the University of Auckland. Data from a comprehensive set of three-dimensional sand waves developing from a flat bed to equilibrium stage were obtained during experimental investigations (SWAT. nz - Sand Waves and Turbulence New Zealand). Two flumes, 0. 44-m-wide and 1. 5-mwide, were utilized for the experiments. Runs were undertaken with different flow depths, median grain sediment sizes, and flow velocities. For this paper two experiments with similar flow conditions and Froude numbers are analyzed in more detail. Side-wall effects and bedform growth are studied. The study is part of a series of studies looking at the phenomenon of submerged sediment-bed-form behaviour. The analyzes show increase in bed-form height with flume width increase. This is mainly caused by the side-walls of the narrower flume imposing a physical restriction to the lateral spread of both the 3-D turbulent flow field and the dune development. The wider flume allowed the full development of bed-form width across the flume for shallow flow. The increase in bed-form growth observed closer to the side-walls is associated with different erosion and deposition patterns closer to the wall. The bed-form growth pattern is not affected by the side walls over roughly the centre 30% for both flumes, when the centreline longitudinal profile is taken as a reference value.