HYDRODYNAMICS AND ACOUSTICS

2018 в—Љ Volume 1 (91) в—Љ Issue 2 в—Љ p. 132-159

I. M. Gorban^*

^* Institute of Hydromechanics of NAS of Ukraine, Kyiv, Ukraine

Modeling of sandpit dynamics in river flows

Gidrodin. akust. 2018, 1(2):132-159

https://doi.org/10.15407/jha2018.02.132

TEXT LANGUAGE: Ukrainian

ABSTRACT

A two-dimensional numerical method for simulating of coupled evolution of the water flow and the bed in open reservoirs is developed considering the mutual influence of the morphological processes. It combines the Kurganov-Noelle-Petrova central upwind scheme for integration of shallow water equations and the fifth-order Weighted Essentially Non-Oscillatory (WENO) Scheme to describe the evolution of bed surface. The bedload sediment transport rate is estimated by power-law Grass formula. Simulation of the test problem on erosion of a conical sand dune in a water flow revealed the longterm stability of the obtained solution, as well as its relevance to the data presented by other researchers. The method was used to calculate the evolution of deep sand quarries on the river bed. The obtained results demonstrate formation of a compound relief form on the bed when the localized hollow is transformed into the system of pits and small mounds moving with the flow. At the same time, the deepening expands across the flow that leads to the formation of extended erosion zones on the river bottom. The angle of spread characterizing the evolution of the quarry is found to depend on the initial quarry depth and water flow parameters and ranges from 20В° to 35В°. The obtained estimates of "survivability" of sand quarries indicate the nonlinear dependence of both the intensity of their filling and motion velocity on the flow parameters. Simulation of free surface evolution revealed an intense wave front generation over the unevenness of the bottom. The shape of this front changes in accordance with the processes occurring at the riverbed. The obtained estimates may be used when organizing the activities to prevent the negative technological and natural phenomena in river water areas initiated by interaction of large-scale bed roughness with hydraulic structures and banks.

KEY WORDS

morphological process, bed surface, sediment transport, sand quarry, angle of spread

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