CAREER: Integrated Experimental and Numerical Modeling Study of Non-uniform Sediment Transport in Meandering Channels

University Of Arizona, Tucson AZ

Investigators

Abstract

Abstract The scientific knowledge on sediment transport in alluvial channels stems from experiments in straight channels. In curved channels, sediment interacts with highly three-dimensional flow and induces point bars and meandering planform evolution. To date, no theory is able to satisfactorily explain and quantify the interactions among flow (mean and turbulence), sediment transport by size fractions, point bar dynamics and the sequential migration of bends. Among many numerical models applied to curved and meandering channels, formulations for sediment transport by size fractions have been based on data from straight laboratory flumes and never tested with sinuous channels. Current understanding of sediment sorting through meandering channels limits the capability of numerical models in simulating the evolution of bed material gradation, bed morphology, and bend planform. Towards a complete understanding of sediment transport in meanders, this project aims to address the following questions: How does flow influence sediment transport? How much does sediment transport deviate from the near-bed mean flow? What are the spatial distributions of sediment load? What are the size gradations of bed load, surface, and substrate material? How do they correlate to sediment transport rate by size fraction? How does spatially varied sediment flux constitute point bar dynamics? How does meandering migration response to the growth or dampening of point bars? Experiments will be conducted in several series of self-formed meandering channels with sinuosities ranging from 1.25 to 3.7. Well-graded sediment mixtures will be fed into these sinuous channels to enable investigation of three-dimensional hydrodynamic flow field, distributions of surface and substrate material, sediment transport characteristics for different size fractions at the streamwise and lateral directions, gradual formation, growth, and dampening of point bars and pools near the apex and channel crossing, planform evolution as bank erodes and point bar progresses. The experimental results will be integrated into a numerical model to simulate the processes of meandering migrations in both experimental flumes and a natural river. The results of this research will contribute to scientific understanding of river meanders and provide valuable guidance in river restoration design. The merit is not only in basic research but also in engineering practice. The project will acquire an experimental facility and a computer model needed for new courses, engage undergraduates in research, establish a longer-standing mentoring program for women students, develop a computer animation exhibition for science museums, and outreach to high school students. The objectives are to encourage creativity and innovation, stress computing in engineering teaching, increase the visibility of women in engineering, and attract most talented high school graduates to Civil Engineering.