HYDRODYNAMICS AND ACOUSTICS

2024 ◊ Volume 3 (93) ◊ Issue 1 ◊ p. 32-66

I. M. Gorban^*, A. S. Koroleva^*

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

Studying the effectiveness of submerged double barriers in protecting coastal technical infrastructure from waves

Gidrodin. akust. 2024, 3(1):032-066

TEXT LANGUAGE: Ukrainian

ABSTRACT

Global climate changes increase the number and intensity of extreme events in the seas and oceans, such as tsunamis, floods, storm surges, etc. They can have catastrophic consequences for coastal areas, manifested in the destruction of civil infrastructure, flooding of recreational areas, and deterioration of the habitat of living organisms. The paper substantiates the effectiveness of a submerged breakwater in the form of two parallel walls, designed to provide economic and ecological protection of the shores of natural reservoirs from the destructive energy of waves. Numerical modeling of the interaction of a soliton wave with two thin submerged barriers, located one behind the other, was performed. The numerical procedure is based on a combination of the method of boundary integral equations, which describes the deformations of the free surface, and the hybrid vortex scheme for modeling the effects caused by the viscosity of the liquid. The correctness of its application is substantiated by comparing the results of calculations with the data of a laboratory experiment performed in the wave trough of the Institute of Hydromechanics of the National Academy of Sciences of Ukraine, as well as with the numerical and experimental data of other authors. The goal is to identify the optimal geometric parameters of the double barrier, both from the point of view of its protective properties and its impact on the environment. The hydraulic quality of the structure as a breakwater is evaluated by the wave energy coefficients of transmission and reflection, as well as the coefficient of energy dissipation. Such a structure is ineffective in comparison with an isolated barrier if the width of the gap between its elements does not exceed one-and-a-half water depths. The optimal distance at which maximum efficiency for energy losses of oncoming waves is obtained makes 2.5 water depth $h$. The study of viscous effects caused by a soliton wave around a double barrier revealed that the vortex field is represented by two large vortices formed by separation flows at the top of each barrier. If the distance between the barriers is less than the water depth, these vortices intensively interact with one another. Therefore, the wave perceives the double barrier as a continuous wide obstacle, which worsens the protective properties of such a structure. The vortex field determines the dynamics of water exchange flows. A protection structure consisting of two impermeable parallel walls, which are located to each other closer than 2.5h, does not contribute to the formation of a reverse flow of water from the coastal zone to the open sea. Therefore, the distance of 2.5h is optimal, both from the point of view of the protective properties of the structure and concerning the preservation of favorable ecology in a limited part of the water area. We assume that the obtained results will contribute to reducing the costs of constructing and exploiting protective structures of this type.

KEY WORDS

surface solitary wave, submerged protective wall, double barrier, method of boundary integral equations, vortex method

REFERENCES