海洋底边界层中实测海流的垂直分布 Ⅱ.潮流边界层

THE VERTICAL DISTRIBUTIONS OF OCEAN CURRENTS IN THE BOTTOM BOUNDARY LAYER OF SHELF SEA Ⅱ.THE BOTTOM BOUNDARY LAYER OF TIDAL CURRENTS

为了满足海洋工程设计的需要 ,作者从理论上研究了海底以上 1— 2m处潮流边界层的结构。把传统上用于稳定海流的底Ekman层理论发展成为用于潮流运动的振荡Ekman边界层 ,给出了潮流Ekman方程的解析解 [式 ( 32 )— ( 35 ) ],提出了对数边界层中潮流运动的方程组 (式 4— 8)及其约束条件 (式 48) ,并给出了潮流Ekman层与潮流对数边界层的匹配条件 (式 43) ,还给出了计算浅海潮流垂直分布的解析表达式 ( 36)— ( 39)。

The observed ocean currents are generally decomposed into two components:residual and tidal currents. In the previous paper (Part I) we discussed the vertical distribution of residual currents with the help of the stationary boundary layer theory. Since the stationary theory cannot be applied to tidal currents due to their oscillatory properties, in this paper we consider both the tidal Ekman layer and logarithmic layer to be an oscillatory boundary layer. The momentum equation of the tidal Ekman layer can be written as i(σ+f) += d d ζ 2K V d + d ζ 2(1) -i(σ-f) -= d d ζ 2K V d - d ζ 2 where the quantity + respresents a velocity vector of constant magonitude whose direction rotates anticlockwise with frequency σ ,when viewed from above; the quantity - likewise represents a velocity with a constant magnitude which rotates clokwise with frequency σ ; f is the Coriolis parameter, K V , the eddy viscosity cofficient; ζ 2 the vertical coordinate in the Ekman layer. Apparently, the equation set (1) can be solved analytically as given in the text. The tidal logarithmic layer equation results in the following equation:  d η d t=^z 0κ 2u 0 e η(η-1)+1+η(- e -η +η+1)u 0[ e η(η-1)+1] d u 0 d t+f^z 0κη 2( e η-η-1)v 0 e η(η-1)+1V 0u 2 0(2) where κ is von Karman's constant equal to 0.4; ^z 0 is the seabed roughness length; ( u 0,v 0 )is the velocity at the top of logarithmic layer, η= ^u 0κ/ ^u * ,u * is the friction velocity.Obviously, equation (2) should be sloved numerically.