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Comparison of the sediment transport formulae according to Bijker and Van Rijn

Author: Jenniskens, M.J.J.
Mentor: D'Angremond, K. · Van Rijn, L.C. · Van der Veer, P. · Van de Graaff, J. · Sistermans, P.G.J. · Sedmoc
Faculty:Civil Engineering and Geosciences
Type:Master thesis
Date:2001-06-01
Publisher: TU Delft, Civil Engineering and Geosciences, Hydraulic Engineering
Keywords: sediment transport formulae · input parameters · input values
Rights: (c) 2001 Jenniskens, M.J.J.

Abstract

Over the years, several computational morphological models have been developed that intend to describe the morphological changes in large coastal zones. Two formulae often used to calculate the sediment transport within these models are those of Bijker (1968) and Van Rijn (1993). These formulae often predict different sediment transport rates for the same input
parameters. Further, they react differently when input parameters are being changed. The objective of this thesis is to give insight in the behaviour of these two formulae due to variations of the input parameters. The differences in outcomes between both formulae and the reaction of the formulae to varying input parameters have been evaluated. A range of values for the input parameters, such as wave height, mean current velocity or grain size, was defined. With these input values, calculations were done to study the influence of a varying input parameter on the resulting total sediment transport according to both formulae. The sediment transport according to these computations is shown in charts. From these charts
the influence of a certain input parameter on the outcomes for the total sediment transport can be evaluated. The change in sediment transport can have its origin in changes of either the bed load or suspended transport or both. For both Bijker's formula and Van Rijn's formula the change in total transport can be attributed mainly to changes in the suspended transport. The concentration distribution rather than the velocity distribution is, in general, responsible for the large variation in suspended transport. The velocity distribution does not affect the outcomes much. The changing shape of the concentration profile is of more impact on the outcomes for the suspended transport than the change in reference concentration. It is not remarkable that the outcomes according to both methods differ, after all both methods use different assumptions and calculation methods. It is therefore interesting to investigate for which input values large differences in results between both methods occur. For this purpose, two sets of input parameters were defined: a set for breaking waves and a set for non-breaking waves. The ratio in calculated total transport between the formula of Bijker and the formula of Van Rijn was calculated. This ratio has been analysed, showing for which input values large ratios can be found. Finally, it has been tried to quantify the influence of input variables on the outcomes for the total sediment transport. Two strongly simplified functions have been formulated approaching the sediment transport according to Bijker's formula and Van Rijn's formula. These functions give an indication of the significance of each of the individual input parameters used in the computation of the sediment transport. They confirm the conclusions drawn from the charts presented in Part B, where the results of the computations are shown in graphs. The functions can also be used to give an indication of the total sediment transport according to the formulae considered in this thesis.

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