NON-HYDROSTATIC MODELLING OF KELVIN-HELMHOLTZ BILLOWS ALONG THE NORTH PASSAGE OF YANGTZE RIVER ESTUARY, CHINA

Chaofeng Tong,Jian Shi,Jinhai Zheng

doi:10.9753/icce.v36.currents.81

Abstract

Induced by velocity shear, Kelvin-Helmholtz (KH) instability arises along an interface of two different fluids. In stratified flows, the KH instability is the first step toward to the onset of intensive mixing in the pycnocline, and it has been thought to be the main mechanism of converting stratified fluids to mixing (Geyer et al., 2010). The direct observation of KH instability in ocean is rare, and a few observations in estuarine and coastal areas are obtained by analyzing the acoustic backscatter profiles from echo sounder. However, the backscatter can only provide qualitative images of the KH billows, which cannot well represent the evolution and influence of KH billows on surrounding density field. Well treatment of vertical variability of velocity and density, non-hydrostatic model is a new and useful tool for the study of K-H instability. In this study, we established a non-hydrostatic model along the North Passage of Yangtze River Estuary to explore the occurrence of KH instability in the domain.

Highlights

Induced by velocity shear, Kelvin-Helmholtz(KH) instability arises along an interface of two different fluids
We established a non-hydrostatic model along the North Passage of Yangtze River Estuary to explore the occurrence of KH instability in the domain
As shown in Figure 1, the model can successfully capture the occurrence of Kelvin-Helmholtz billow in the lower part of the North Passage

Summary

Introduction

Kelvin-Helmholtz(KH) instability arises along an interface of two different fluids. Well treatment of vertical variability of velocity and density, non-hydrostatic model is a new and useful tool for the study of K-H instability. We established a non-hydrostatic model along the North Passage of Yangtze River Estuary to explore the occurrence of KH instability in the domain. Model Setup A non-hydrostatic model NHWAVE is employed to establish the model, which is a parallelized model based on the incompressible Naiver-Stokes equations in σ coordinate system (Ma et al, 2012).

Results

Conclusion