The atmosphere-ocean heat engine is simply illustrated in the classic 'annulus experiment' (click on image for video). Here
seen from above, the fluid is contained between cold 'polar' wall and warm 'tropical' wall, on a rotating
platform. The experiment is readily carried out with a salad bowl and soup-can of ice on a pawn-shop record player. Rather than
simply convecting as in a Hadley cell, the fluid develops two jet streams that carry heat meridionally, interlacing with long
waves
about isolated eddies that march eastward round the annulus. The waves are generic cousins of the Rossby waves seen elsewhere on
this page.
OPTICAL ALTIMETRY: IMAGING THE PRESSURE, VELOCITY AND VORTICITY IN A
ROTATING FLUID
NEWS! A complete software package for analysis of AIV (color
altimetric images) is now available from Yakov Afanasyev, at the
Physics Department of Memorial University, St. Johns Newfoundland,
Canada. Once the
system is assembled (involving a color transparency and a light source
and camera mounted above the rotating table, or with mirror to double
the optical path, mounted at the height of the fluid), this software
makes efficient calculations of surface height field, geostrophic and
ageostrophic pressure and velocity, and vorticity and potential
vorticity. For examples see the recent JFM preprint of Afanasyev,
Rhines and Lindahl under Recent Papers on our library page, here.
Contact
yakov@physics.mun.ca, and on the web www.physics.mun.ca/~yakov/
GFD lab altimetric images of turbulent flow driven by buoyant central
source, color-coded
by slope (I. Afanasyev); Click to enlarge
above, vertical vorticity in cylinder wake
Image by P.Rhines, E.Lindahl; click to download animation, 1 Mb Quicktime
format
A new way of looking at rotating fluids
(here, color image above is the field of
surface elevation with baroclinic turbulence and jets due to a source of low-density water at the
center, on a laboratory polar beta-plane (North Pole at the center). Middle image is
vertical vorticity in cylinder
wake, left: 'eastward' translation of cylinder; right, 'westward' translation of cylinder;
black: cyclonic, white: anticyclonic.
Bottom image is a field of periodically-forced Rossby waves;
the amplitude of the surface height features ranges from 1 micron to 1
mm., shown with knife-edge optical altimetery as a side-lit image).
See Outputs link to find new manuscript.
(for discussion of Rossby waves
click
here.
For recent papers go to 'Outputs', here.
For a recently approved grant proposal describing developments and plans,
click here.
Standing Rossby waves in the lee of a spherical-cap
mountain
(at 2
o'clock) with particle streaks superimposed.
The grey-shading shows the pressure
field (the elevation of the water surface), which is also the
stream-function for the geostrophic flow. The flow is quasi-steady. 1
m. diameter cylinder with
paraboloidal free surface, rotating at 2.3 radians/sec. Driven by an
eastward (i.e., counter-clockwise) solid-body rotation of the fluid,
which is maintained by ramping down the table rotation rate.
The most energetic flow
features are the spiral jet/wake structure at the mountian. The
'tip-jet' at Cape Farewell Greenland may be an analogous feature from
the subpolar Atlantic. A 'Lighthill block' extends eastward around
circular latitude lines, upstream
of the mountain. Note the
ruddy moon-scape in this blocked region, which is a field of small
evaporative convection cells
('clouds' rotating cyclonically) east of the mountain, surrounded by
weak convective rolls in the region of shear.
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Personnel
-
Peter B. Rhines: this serves also as his personal web page.
-
Eric
G. Lindahl (Research Engineer and instructor)
- Bob Koon (Research Engineer and instuctor)
- Iakov Afanasyev, sabbatical
visitor from Memorial University, St. Johns
Newfoundland, 2006.
- Alex Mendez (UW undergraduate in Physics)
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2007 visitors and students:
- Caitlin Whalen (summer; Reed
College physics major, class of 2008): Rossby waves and the Stommel-Arons-Faller
deep circulation (below)
- Jonathan Wai (summer; UW Aerospace Engineering, class of 2007): altimetric
imaging of a cylindrical shear layer interacting with inertial waves (click on
images below).
- Laure Grignon (WUN visiting grad student from Univ. of
Southampton, England, Sept-Dec 2007)
- Alex Mendez (UW undergraduate in Physics and Mathematics)
Satellite altimetry and GFD lab altimetry
2006 visitors and students:
- Elin Darelius (3 mo. visiting grad student from University of
Bergen)
Downslope abyssal flows modelled in the lab
- Alex Mendez (UW undergraduate in Physics and Mathematics)
Satellite altimetry and GFD lab altimetry
- Iakov Afanessiev, 12 mo. - sabbatical visitor from Memorial
University, St. Johns
Newfoundland.
Vortex dynamics, bubble circulations, colorometric
optical
altimetry, spontaneous imbalance
2004 visitors and students:
-
Adam Van Etten (UW undergraduate in physics, 2004))
PIV (particle imaging velocimetry implementation for rotating
fluid experiments
-
Alex Mendez(UW undergraduate in Physics 2003-2006)
Imaging rotating-fluid circulations with optical methods
2002 visitors and students:
-
Race Roberson (UW undergraduate in physics))
Source-sink flows with rotation: a model of the Arctic Ocean
circulation.
-
Dave Peterson(UW undergraduate in Aerospace Engineering)
Lee waves/downslope wind/mixed rotors in stratified flow over a mountain
(with critical
level at mid-height). Click to enlarge.
Summer 2001 visitors and students:
-
Zong Li (UW undergraduate in Computer Science))
Pollutant flows in ground water
-
Amit Mahtani (UW first-year undergraduate))
Design and construction of a vertical density profileer
-
Dave Peterson(UW undergraduate in Aerospace
Engineering)
Dynamics of rotating hemispherical bubbles
Summer 2000 visitors and students:
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Rossby waves and a polar vortex
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Deep Convection in the Subpolar Zone
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Vortices formed beneath a spinning disk on the top of a rotating fluid
(click)
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Ripples, waves, hydraulics and flows round bumps...at all scales
(click image for more).
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A brief discussion of storm tracks
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Overturning Circulations and Convection: Meridional overturning fluids
driven by stress or buoyancy Click
image for more.
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What is Oceanography?
A brief essay
(2000); others may be found below ('OUTPUTS')
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The GFD lab moved in March 2000 to a new 1300 sq. ft facility in the newly
completed Ocean Sciences Building.
The lab has a specially constructed vibration isolation pad for the two large
rotating tables, with a high-bay extending nearly 30 feet upward, to facilitate
laser imaging of rotating fluid surface, photography and lighting. We have a
1100 sq ft. teaching laboratory in Ocean Teaching Building, where projects
courses, demonstrations and
school visits occur. There is a re-entrant pumped flume there, and an
estuary-model flume.
Parker MacCready ,
William Wilcock, and Alex
Horner-Devine, all have nearby fluids labs and related activities: a rare
concentration of real fluid experimentation. Not far away also is the
fluids lab
of Aero/Astronaut Bob
Breidenthal. 
undular
bore two stories high, as one wall of the building. 
Chlorophyll during late spring bloom round Tasmania
(27xi1981), 1 km resolution (Courtesy of CZCS/SeaWiFS projects)
