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Secondary circulation

About: Secondary circulation is a research topic. Over the lifetime, 414 publications have been published within this topic receiving 13255 citations.


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TL;DR: In this paper, the secondary circulation of a hurricane-like vortice is modeled as a two-dimensional stream function dipole response of Eliassen's diagnostic technique, modified by both the spatial variations of the vortex structure and the influences of boundary conditions.
Abstract: Eliassen's (1951) diagnostic technique is used to calculate the secondary circulation induced by point sources of heat and momentum in balanced, hurricane-like vortices. Scale analysis reveals that such responses are independent of the horizontal scale of the vortex. Analytic solutions for the secondary circulation are readily obtained in idealized barotropic vortices, but numerical methods are required for more realistic barotropic and baroclinic vortices. For sources near the radius of maximum wind, the local, two-dimensional, streamfunction dipole response of Eliassen is modified by both the spatial variations of the vortex structure and the influences of boundary conditions. The secondary flow advects mean-flow buoyancy and angular momentum and thus leads to a slow evolution of the vortex structure. In weak systems (maximum tangential wind <35 m s−1), the restraining influences of structure and boundaries lengthen the time scale of the vortex evolution. In stronger vortices, the horizontal sc...

535 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of topographically induced velocity changes on the cross-stream flow pattern was analyzed in a channel with a constant bottom topology, where the velocity component near the bed and the pattern of boundary shear stress can be estimated by assuming fluid acceleration to be small.
Abstract: In a channel with bed topography that does not vary in the downstream direction, a secondary circulation composed of outward flow at the surface and inward flow near the bottom extends across the entire width. If the curvature is constant, the cross-stream velocity component near the bed and the pattern of boundary shear stress can be estimated by assuming fluid accelerations to be small. Unfortunately, this procedure cannot be used in analyzing the flow through natural river meanders, or through channels with downstream constant bottom topography but with rapidly changing curvature. In these latter cases, effects arising from bed- and bank-induced momentum changes must be accounted for. Evidence for a substantial topographically induced alteration in the cross-stream flow pattern relative to that for the analogous constant bottom topography case is provided through new analyses of several sets of laboratory and field data. Shoaling over the point bar in the upstream part of the bend is shown to force the high-velocity core of the flow toward the pool. This is accomplished by a convective acceleration-caused decrease in the cross-stream water surface slope and a resulting dominance of the vertically averaged centrifugal force. The primary effect is a velocity component toward the outside or concave bank throughout the flow depth over the upstream, shallow part of the point bar and an outward component of boundary shear stress in this region. The channel curvature-induced inward component of boundary shear stress consequently is confined to 20 or 30% of the channel width at the pool. Outward transfer of momentum over the point bar, as manifested by a rapid crossing of the high-velocity core from the inside bank to the outside one, contributes to an enhanced decrease in boundary shear stress along the convex side of the stream as the top of the bar is approached. Forces arising from topographically induced spatial accelerations are of the same order of magnitude as the downstream boundary shear stress and water surface slope force components, so they must be modeled as zero-order, not first- or second-order, effects.

423 citations

Journal ArticleDOI
TL;DR: In this article, the authors consider the frictionless, axisymmetric, balanced flow occurring in a thermally forced vortex on an f-plane and derive the diagnostic equation for the forced secondary circulation.
Abstract: We consider the frictionless, axisymmetric, balanced flow occurring in a thermally forced vortex on an f-plane. Following Eliassen (1952) we derive the diagnostic equation for the forced secondary circulation. This equation contains the spatially varying coefficients A (static stability), B (baroclinity), C (inertial stability), and the thermal forcing Q. Assuming that A is a constant, B = 0, and that C and Q are piecewise constant functions of radius, we obtain analytical solutions for the forced secondary circulation. The solutions illustrate the following points. 1) For a given Q an increase in inertial stability leads to a decrease in the forced secondary circulation and a change in the radial distribution of local temperature change, with enhanced ∂θ/∂t; in the region of high inertial stability. 2) Lower tropospheric tangential wind accelerations are larger inside the radius of maximum wind, which leads to a collapse of the radius of maximum wind. 3) The fraction of Q which ends up as ∂θ/∂t;...

383 citations

Journal ArticleDOI
TL;DR: In this article, an upper bound on wind speed was derived by equating the generation of energy in this cycle to boundary layer dissipation, and this bound depends on the degree of thermodynamic disequilibrium between the tropical ocean and atmosphere, on the difference between sea surface and outflow absolute temperatures, and also on the ratio between the enthalpy exchange and surface drag coefficients.
Abstract: The energy cycle of the mature hurricane resides in the secondary circulation that passes through the storm’s eyewall. By equating the generation of energy in this cycle to boundary layer dissipation, an upper bound on wind speed is derived. This bound depends on the degree of thermodynamic disequilibrium between the tropical ocean and atmosphere, on the difference between sea surface and outflow absolute temperatures, and also on the ratio between the enthalpy exchange and surface drag coefficients. Such a bound proves to be an excellent predictor of maximum wind speeds in two different axisymmetric numerical models and does not appear to depend on the existence of the hurricane eye. But further consideration of the detailed dynamics of the eye and eyewall show that the intensification of hurricanes is accelerated by feedbacks associated with a component of eye subsidence forced by radial turbulent diffusion of momentum. This radial momentum diffusion is an inevitable by-product of the strong fr...

277 citations

Journal ArticleDOI
TL;DR: In this paper, airborne Doppler radar measurements are used to determine the horizontal winds, vertical air motions, radar reflectivity and hydrometer fall speeds over much of the inner core region (within 40 km of the eye) of Hurricane Alicia (1983).
Abstract: Airborne Doppler radar measurements are used to determine the horizontal winds, vertical air motions, radar reflectivity and hydrometer fallspeeds over much of the inner-core region (within 40 km of the eye) of Hurricane Alicia (1983). The reconstructed flow field is more complete and detailed than any obtained previously. The data show both the primary (azimuthal) and secondary (radial-height) circulations. The primary circulation was characterized by an outward sloping maximum of tangential wind. The secondary circulation was characterized by a deep layer of radial inflow in the lower troposphere and a layer of intense outflow above 10 km altitude. The rising branch of the secondary circulation was located in the eyewall and sloped radially outward. Discrete convective-scale bubbles of more intense upward motion were superimposed on this mean rising current, and convective-scale downdrafts were located throughout and below the core of maximum precipitation in the eyewall. Precipitation particle...

268 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20237
20228
202111
202012
201912
201820