Stratification Effects in a Bottom Ekman Layer

被引:65
|
作者
Taylor, John R. [1 ]
Sarkar, Sutanu [1 ]
机构
[1] Univ Calif San Diego, Dept Mech & Aerosp Engn, La Jolla, CA 92093 USA
关键词
D O I
10.1175/2008JPO3942.1
中图分类号
P7 [海洋学];
学科分类号
0707 ;
摘要
A stratified bottom Ekman layer over a nonsloping, rough surface is studied using a three-dimensional unsteady large eddy simulation to examine the effects of an outer layer stratification on the boundary layer structure. When the flow field is initialized with a linear temperature profile, a three-layer structure develops with a mixed layer near the wall separated from a uniformly stratified outer layer by a pycnocline. With the free-stream velocity fixed, the wall stress increases slightly with the imposed stratification, but the primary role of stratification is to limit the boundary layer height. Ekman transport is generally confined to the mixed layer, which leads to larger cross-stream velocities and a larger surface veering angle when the flow is stratified. The rate of turning in the mixed layer is nearly independent of stratification, so that when stratification is large and the boundary layer thickness is reduced, the rate of veering in the pycnocline becomes very large. In the pycnocline, the mean shear is larger than observed in an unstratified boundary layer, which is explained using a buoyancy length scale, u(*)/N(z). This length scale leads to an explicit buoyancy-related modification to the log law for the mean velocity profile. A new method for deducing the wall stress based on observed mean velocity and density profiles is proposed and shows significant improvement compared to the standard profile method. A streamwise jet is observed near the center of the pycnocline, and the shear at the top of the jet leads to local shear instabilities and enhanced mixing in that region, despite the fact that the Richardson number formed using the mean density and shear profiles is larger than unity.
引用
收藏
页码:2535 / 2555
页数:21
相关论文
共 50 条
  • [1] Influence of Stratification and Bottom Boundary Layer on the Classical Ekman Model
    Santander-Rodriguez, Viviana
    Diez-Minguito, Manuel
    Espinoza-Andaluz, Mayken
    JOURNAL OF MARINE SCIENCE AND ENGINEERING, 2022, 10 (10)
  • [2] Direct and large eddy simulations of a bottom Ekman layer under an external stratification
    Taylor, John R.
    Sarkar, Sutanu
    INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW, 2008, 29 (03) : 721 - 732
  • [3] Organization of stratification, turbulence, and veering in bottom Ekman layers
    Perlin, A.
    Moum, J. N.
    Klymak, J. M.
    Levine, M. D.
    Boyd, T.
    Kosro, P. M.
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 2007, 112 (C5)
  • [4] The bottom Ekman layer and the apparent violation of the maximum principle
    Gildor, Hezi
    GEOPHYSICAL AND ASTROPHYSICAL FLUID DYNAMICS, 2008, 102 (06): : 593 - 599
  • [5] Study of the effects of Ekman dynamics in the bottom boundary layer on the Black Sea continental slope
    Zatsepin, A. G.
    Kremenetskiy, V. V.
    Podymov, O., I
    Ostrovskii, A. G.
    RUSSIAN JOURNAL OF EARTH SCIENCES, 2020, 20 (01):
  • [6] URBAN EKMAN LAYER OBSERVED DURING NEUTRAL AND STABLE STRATIFICATION
    DOBBINS, RA
    GILBERT, AJ
    NEWMAN, GR
    COCHRAN, HB
    BULLETIN OF THE AMERICAN PHYSICAL SOCIETY, 1973, 18 (11): : 1477 - 1477
  • [7] Time-dependent motions and the nonlinear bottom Ekman layer
    Brink, KH
    JOURNAL OF MARINE RESEARCH, 1997, 55 (04) : 613 - 631
  • [8] Internal gravity waves generated by a turbulent bottom Ekman layer
    Taylor, John R.
    Sarkar, Sutanu
    JOURNAL OF FLUID MECHANICS, 2007, 590 : 331 - 354
  • [9] Estimation of Eddy Viscosity Profile in the Bottom Ekman Boundary Layer
    Cao, An-Zhou
    Chen, Hui
    Fan, Wei
    He, Hai-Lun
    Song, Jin-Bao
    Zhang, Ji-Cai
    JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY, 2017, 34 (10) : 2163 - 2175
  • [10] OBSERVATIONS AND SIMULATION OF A BOTTOM EKMAN LAYER ON A CONTINENTAL-SHELF
    DICKEY, TD
    VANLEER, JC
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, 1984, 89 (NC2): : 1983 - 1988