Internal Waves Generated by Tidal Flows over a Triangular Ridge with Critical Slopes  

作　　者：NIE Yuhua CHEN Zhiwu XIE Jieshuo XU Jiexin HE Yinghui CAI Shuqun 

机构地区：[1]South China Sea Information Center of State Oceanic Administration,Guangzhou 510310,China [2]State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences,Guangzhou 510301,China [3]University of Chinese Academy of Sciences,Beijing 100049,China [4]Institution of South China Sea Ecology and Environmental Engineering,Chinese Academy of Sciences,Guangzhou 510301,China

出　　处：《Journal of Ocean University of China》2019年第5期1005-1012,共8页中国海洋大学学报（英文版）

基　　金：supported by the Key Research Program of Frontier Sciences, CAS (No. QYZDJ-SSWDQC034);the National Natural Science Foundation of China (Nos. 41430964, 41521005, 41776007, 41506005);the Pearl River S&T Nova Program of Guangzhou (No. 201610010012);the Youth Innovation Promotion Association CAS (No. 2018378);No. ISEE2018PY05 from CAS

摘　　要：Direct numerical simulations are performed to investigate the generation of internal waves by tide-topography interaction in a lab-scale model.The bottom topography is a triangular ridge with two critical slopes.With increasing tidal forcing,subharmonic instabilities are identified,which cause internal wave beams to become unstable and turbulent.Kinetic energy densities in the upward going beams from the ridge top are stronger than those from the ridge bottom,whereas the reverse is true for the energy flux.This disparity between energy and energy flux is due to the existence of strong pressure disturbances near the ridge bottom.On each side of the critical ridge,there exists an amphidromic point,from which internal wave beams are emitted in opposite directions.The calculated energy conversion rate scales linearly with the square of the forcing amplitude and agrees within 13%of theoretical prediction,even when turbulence occurs.The fraction of radiated baroclinic energy becomes saturated in the range of low excursion parameter considered,which agrees with the behavior in large-scale systems wherein mixing parameterizations must be used.The present work enriches the studies on the generation of internal waves over a critical triangular ridge.Direct numerical simulations are performed to investigate the generation of internal waves by tide-topography interaction in a lab-scale model. The bottom topography is a triangular ridge with two critical slopes. With increasing tidal forcing, subharmonic instabilities are identified, which cause internal wave beams to become unstable and turbulent. Kinetic energy densities in the upward going beams from the ridge top are stronger than those from the ridge bottom, whereas the reverse is true for the energy flux. This disparity between energy and energy flux is due to the existence of strong pressure disturbances near the ridge bottom. On each side of the critical ridge, there exists an amphidromic point, from which internal wave beams are emitted in opposite directions. The calculated energy conversion rate scales linearly with the square of the forcing amplitude and agrees within 13% of theoretical prediction, even when turbulence occurs. The fraction of radiated baroclinic energy becomes saturated in the range of low excursion parameter considered, which agrees with the behavior in large-scale systems wherein mixing parameterizations must be used. The present work enriches the studies on the generation of internal waves over a critical triangular ridge.

关 键 词：INTERNAL WAVE beam parametric SUBHARMONIC instability INTERNAL WAVE ENERGETICS tide-topography interaction 

分 类 号：P[天文地球]