A Numerical Study of the Forces on Two Tandem Cylinders Exerted by Internal Solitary Waves

Yin Wang,Hai Zhu,Hongwu Tang,Gang Wei,Lingling Wang

doi:10.1155/2016/9086246

Abstract

A three-dimensional numerical wave flume is employed to investigate the forces exerted by internal solitary waves (ISWs) on a pair of circular cylinders in tandem arrangement, using large-eddy simulation (LES) model. The effect of the centre-to-centre distance (L) ranging from 1.5 to 5 diameters (D) is studied for various ISWs amplitudes (ηa) in the two-layer fluid system. Vertical-averaged vorticity distribution and vertical-averaged pressure gradient distribution in each layer are presented to investigate the different hydrodynamic interference between cylinders and the ISWs forces on each cylinder at variousL. Furthermore, the force behaviors of the two cylinders are also compared with that of an isolated cylinder in the same environment. The interaction between the two piles occurs in both layers, and it is found that, for1.5≤L/D<3.5, strong mutual interference appears between two cylinders; for3.5≤L/D<5, the two cylinders continue to influence each other in a weak-interference state; forL/D≥5, the interaction gradually decreases into a noninteracting state. This paper tries to provide some references to structural arrangement of double-cylinder structure and grouped-cylinder structure in stratified flow environment.

Highlights

In oceans, estuaries, and lakes, the stable stratification of density happens while the fluid density changes along with the depth due to the variations of temperature, salinity, and other environmental factors
The flow field largely depends on Reynolds number, range of which covers 7800 ≤ Re = umaxD/V ≤ 12000 for different dimensionless Internal solitary waves (ISWs) amplitudes ηa/H ranging from 0.12 to 0.215, when it comes to flow around a single circular cylinder [30], while as to the case of two tandem cylinders, the dimensionless centre-to-centre distance L/D plays a decisive role [31, 32]
18(a) and 18(b), we find that the instantaneous verticalaveraged adverse pressure gradient (Zone B) in front of Pile2 is obviously weakened by the existence of Pile1

Summary

Introduction

Estuaries, and lakes, the stable stratification of density happens while the fluid density changes along with the depth due to the variations of temperature, salinity, and other environmental factors. Internal solitary waves (ISWs) with different amplitudes may be produced by a tiny or weak perturbation in such stable stratified environment [1]. Based on the monitoring and measured data collected from the South China Sea, strong underwater currents caused by internal waves could be a serious threat to underwater structures, such as oil drilling platforms or supporting cylinders [2]. Ermanyuk and Gavrilov [3] experimentally studied the hydrodynamic loads exerted by ISW on a submerged circular cylinder in a two-layer system and discovered the locations of the maximum and minimum horizontal loads on the cylinder. Wei et al [4] manufactured a new wave-maker to excite the ISWs and developed a measurement technique of hydrodynamic load to determine the interaction characteristics between IWs and an isolated cylindrical body in the tank

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Conclusion