Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 1/8/2001
Publication Date: N/A
Technical Abstract: The interactions between fluid flow and different sediment size fractions in bimodal mixtures controls sediment transport, grain size sorting, flow resistance and the depositional characteristics of these sediments. This paper presents results of flume experiments conducted using a bimodal sediment mixture (grain size ranging from 0.177 to 26.9 mm) over a range of discharges at two flow depths. Various measurements were taken under equilibrium conditions to define the sedimentological and hydraulic characteristics of the bedforms generated. Results show that with increasing boundary shear stress, ripples, bedload sheets and low-relief bed waves are generated. Velocity and turbulence parameters (e.g. eddy viscosity, mixing length and turbulence intensity) will be detailed over the various bedforms, and compared with previous work. The non- logarithmic nature of vertical profiles of downstream velocity, and the presence of shear layers shed from coarse particles and bedform crests, generate a complex flow field. Furthermore, the development and migration of these bedforms impacts greatly on the sediment flux, surface sorting patterns, and turbulent flow structure.