Physical and numerical modelling study of meandering in fluvial rivers

Kuang, Hongwei 2011. Physical and numerical modelling study of meandering in fluvial rivers. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

A study has been taken to investigate the channel development especially fluvial river with meandering thalweg. The study included the physical model with steady inflow and unsteady inflow in the lab, and numerical model to simulate the development process, considering the bank erosion and secondary flow. In the study of channel development with physical model, a series of tests have been carried out to model the fluvial river with different flume slope, flow rate and channel section size. The meandering thawleg channel development process was carefully observed and from results in the lab, channels only had curved boundaries with meandering thalweg, not the real meandering river. Many characteristics of fluvial river in the nature like ripple- pool unit, point bar have been modelled successfully. Then different parameters like slope, flow rate and channel size were tested independently to see their effect on channel morphology. From experiments, it is confirmed that slope is key factor to distinguish straight, meandering and braided channels. Flow rate and section size were also discussed. From the discussion of different controlling parameters, it is found that the essential control factor is Froude number. Tests with unsteady inflow were then carried out to model the real hydrology process as that in nature. Gradually varied unsteady inflow and rapidly varied unsteady inflow were achieved by controlling the frequency of pump. Bed profile of channel after operation was recorded by Bed Profiler. Developments tell that steady inflow could deep channel and unsteady inflow has more effect on bank erosion and makes channel wider. It is concluded from bed profiles, steady inflow produces stable ripples, smooth point bars, curved channel banks. Rapidly varied flow got straight channel, wider upstream. Gradually varied flow got unstable ripple in the main channel and deepest pools. Finally numerical modelling considering bank erosion and secondary flow was developed to simulate the tests. Bank erosion model comes from previous research and secondary flow was considered based on the balance of force in the transverse direction on Cartesian coordinate system without the constraint of constant radius of curvature. The modelling results have a good agreement with physical model for steady inflow and unsteady inflow with different channel size and slope.

Item Type:	Thesis (PhD)
Status:	Unpublished
Schools:	Engineering
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Uncontrolled Keywords:	Meandering; Fluvial river; Secondary flow; Bank erosion; Physical model; Numerical model; Geomorphology; Sinuosity; Bar; Deposition.
Date of First Compliant Deposit:	30 March 2016
Last Modified:	19 Mar 2016 22:22
URI:	https://orca.cardiff.ac.uk/id/eprint/13543

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