Neutrally Stratified Turbulent Ekman Boundary Layer: Universal Similarity for a Transitional Rough Surface

This experimental study focuses on the effect of horizontal boundaries with pyramid-shaped roughness elements on the heat transfer in rotating Rayleigh–Bénard convection. It is shown that the Ekman pumping mechanism, which is responsible for the heat transfer enhancement under rotation in the case of smooth top and bottom surfaces, is unaffected by the roughness as long as the Ekman layer thickness $\unicode[STIX]{x1D6FF}_{E}$ is significantly larger than the roughness height $k$. As the rotation rate increases, and thus $\unicode[STIX]{x1D6FF}_{E}$ decreases, the roughness elements penetrate the radially inward flow in the interior of the Ekman boundary layer that feeds the columnar Ekman vortices. This perturbation generates additional thermal disturbances which are found to increase the heat transfer efficiency even further. However, when $\unicode[STIX]{x1D6FF}_{E}\approx k$, the Ekman boundary layer is strongly perturbed by the roughness elements and the Ekman pumping mechanism is suppressed. The results suggest that the Ekman pumping is re-established for $\unicode[STIX]{x1D6FF}_{E}\ll k$ as the faces of the pyramidal roughness elements then act locally as a sloping boundary on which an Ekman layer can be formed.

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Baroclinic Instability and Frontogenesis with Ekman Boundary Layer Dynamics Incorporating the Geostrophic Momentum Approximation

Journal of the Atmospheric Sciences ◽

10.1175/1520-0469(1983)040<2630:biafwe>2.0.co;2 ◽

1983 ◽

Vol 40 (11) ◽

pp. 2630-2638 ◽

Cited By ~ 9

Author(s):

William Blumen ◽

Rongsheng Wu

Keyword(s):

Boundary Layer ◽

Baroclinic Instability ◽

Ekman Boundary Layer ◽

Momentum Approximation ◽

Boundary Layer Dynamics

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Dynamics of nonlinear baroclinic Ekman boundary layer

Advances in Atmospheric Sciences ◽

10.1007/bf02657932 ◽

1986 ◽

Vol 3 (4) ◽

pp. 424-431 ◽

Cited By ~ 1

Author(s):

Liu Qinyu ◽

Qin Zenghao

Keyword(s):

Boundary Layer ◽

Ekman Boundary Layer

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Wave boundary layers in a stably-neutrally stratified ocean

Океанология ◽

10.31857/s0030-1574592201-207 ◽

2019 ◽

Vol 59 (2) ◽

pp. 201-207

Author(s):

G. M. Reznik

Keyword(s):

Boundary Layer ◽

Asymptotic Solution ◽

Boundary Layers ◽

Ocean Bottom ◽

Linear Evolution ◽

Term Evolution ◽

Stratified Ocean ◽

Wave Boundary ◽

Neutrally Stratified

The theory of wave boundary layers developed in [7], is generalized to the case of stably-neutrally stratified ocean consisting of upper homogeneous and lower stratified layers. In this configuration, in addition to the boundary layers near the ocean bottom and/or surface, a wave boundary layer develops near the interface between the layers in the lower stratified part of basin. Each the boundary layer is a narrow domain characterized by sharp, growing in time, vertical gradients of buoyancy and horizontal velocity. As in [7], the near interface boundary layer arises as a result of free linear evolution of rather general initial fields. An asymptotic solution describing the long-term evolution is presented and compared to exact solution; the asymptotic solution approximates the exact one fairly well even on not very large times.

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