Experimental Study on Turbulent Entrainment in an Enclosed Density Stratified Flow owing to Wind Action

风作用引起的封闭密度分层流湍流夹带的实验研究

• 批准号: 61560270
• 负责人: MORI Ken
• 金额: $ 1.34万
• 依托单位: Kyushu University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1986
• 资助国家: 日本
• 起止时间: 1986 至 1987
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-61560270/
• 关键词: Turbulent flow; Entrainment; Stratified flow; 吹送流; 2成層流

A study is made of the interface turbulent entrainment in a two-layered density stratified flow owing to an imposed surface wind stress.Observed entrainment velocity : (1) When the buoyancy effeet is strong and the wind stress is weak, the entrainment velocity is small. (2) Mechanism of entrainment phenomenon are classified three types, which are diffusion,internal wave breaking and penetrating type.Turbulent structure : (1) lntegral scale and organized large scale vortex are existed in the upper turbulent layer. (2) A strong intermittent turbulence,which is short life time,influences entrainment velocity. (3) The kinetic turbulent energy equation at the interface is effectively to introduce the entrainment velocity law.Decission of entrainment velocity law : By using the parameterization of kinetic turbulent energy equation, We obtained an equation for wind-induced entrainment velocity,u_e/u_*=0.039(7.694+R_<i*>^<1/2>)/R_<i*>-2.5).Where Ri* is an over all Richardson number with a water friction velocity u_*, R_<i*>=<DELTA><rho>gh/<rho>u_*^2,u_e is the entrainment velocity, <DELTA><rho> is the density difference between upper and lower layer, g is the gravitational acceleration , and h is the upper layer depth.

研究了两层密度分层流中由于施加表面风应力而产生的界面湍流夹带。观测到的夹带速度： (1) 当浮力作用较强而风应力较弱时，夹带速度较小。 (2)夹带现象机理分为扩散型、内波破碎型和穿透型三种类型。 湍流结构： (1)上层湍流层存在整体尺度和有组织的大尺度涡旋。 (2)强烈的间歇性湍流影响了夹带速度，且其寿命短。 (3) 界面处的动湍流能方程有效地引入了夹带速度定律。夹带速度定律的判定：利用动湍流能方程的参数化，我们得到了风致夹带速度方程u_e/u_ *=0.039(7.694+R_<i*>^<1/2>)/R_<i*>-2.5)。其中 Ri* 是总体理查森数与水的摩擦速度 u_*，R_<i*>=<DELTA><rho>gh/<rho>u_*^2，u_e 为夹带速度，<DELTA><rho> 为上层密度差下层，g 为重力加速度，h 为上层深​​度。