Plenary
Lecture
Models of Aerodynamics and Physics of Hurricanes
Professor A. I. Leonov
The University of Akron, Akron
OH 44325-0301, U.S.A.
E-mail:
leonov@uakron.edu
Abstract: Theoretical models have been developed to
describe the aerodynamics and physics in quasi-steady
hurricanes moving over open seas. The vertical structure
of hurricane was modeled as consisting of lower,
hurricane boundary layer (HBL) and upper,
quasi-adiabatic layer, connected by a thin condensation
layer in the eye wall region. Except the friction at the
air/sea interface, the modeling avoided the common
turbulent approximations, while explicitly or implicitly
used basic stability constraints.
Based on observations, it was assumed that the
hurricanes propagate along the warm air bands located
over the warm oceanic currents, and under action of
"sailing" wind. It was also assumed that the mass,
humidity, momentum, and angular momentum of air are
transferred from the lower to upper hurricane layers
through the hurricane eye wall.
The air wind in HBL is highly affected by several
physical processes, which have also been analyzed: (i) a
specific oceanic wave – air interaction, (ii)
evaporation at the sea surface, (iii) horizontal thermal
flux from the warm air band to the hurricane core, and
(iv) sudden condensation at the upper boundary of HBL,
which is treated similar to slow combustion. Aerodynamic
analyses of HBL resulted in space distributions of
dynamic and thermodynamic variables. Additionally, a set
of integral balance relations established for HBL,
allowed expressing the key hurricane parameters via the
horizontal temperature drop and sailing wind speed,
which are considered to be given.
The HBL model was coupled with the model of upper AL of
hurricane. Analysis of AL established a stability
constraint for existence of steady hurricane, and
resulted in analytical formulas for space distributions
of dynamic variables. The values of key hurricane
variables calculated using the coupled model, seem to be
realistic.
Several observed effects have been explained and
quantitatively described using this modeling. They
include: (i) change in direction of hurricane angular
velocity from cyclonic in lower part of hurricane to
anti-cyclonic in the upper one, (ii) change in radial
direction of radial wind component from centripetal in
the lower part of hurricane to the centrifugal in its
upper part, (iii) change in the radial distribution of
angular momentum from radially increased in HBL to a
constant value in AL, and (iv) sudden increase of
temperature at the upper part of HBL.
The following three-step model of hurricane genesis and
maturing in sub-tropical zones has been proposed and
analyzed: (i) a sudden formation of plume; (ii) rotating
the plume initiated by the horizontal component of
trading wind, and (iii) propagation of external boundary
of rotated plume due to the Kelvin-Helmholtz instability
and under action of Coriolis force. A simple model
showed that outward propagation of just formed
rotational plume is possible only if the initial
rotation of plume is cyclonic. The model calculations
demonstrate very realistic features as compared with
observations.
Based on these models, a simple idea of hurricane
destabilizing by flights of supersonic jets has been
proposed.
Brief Biography of the Speaker:
Arkady I. Leonov is a full professor at the Department
of Polymer Engineering, and adjunct professor of applied
mathematics at the University of Akron, Ohio, USA. He
worked in broad scientific areas: classic and polymer
related continuum mechanics of solids and liquids,
geophysical fluid mechanics, polymer rheology and
polymer fluid mechanics, polymer physics and physico-chemistry,
polymer processing, and mathematical sociology. He
authored and co-authored over 200 scientific papers
published in reviewed journals, made numerous
presentations at national and international conferences,
published alone or with colleagues' four scientific
monographs and four book chapters. He is a member of
Society of Rheology, American Academy of Mechanics, and
Honorable Member of British Society of Rheology. The
presentation topics have been preliminary published in
Electronic Arxiv Journal, Physics of Atmosphere and
Ocean, 2008.
|