Welcome to Guenter Ahlers' Group
Department of Physics and ITST
University of California, Santa Barbara, CA 93106
Our group conducts research in two distinct subfields
of experimental condensed matter physics. They are:
Turbulence in a fluid heated from below
When a fluid is heated from below, convection will occur when the temperature gradients are large enough. At even much larger temperature differences, the convective flow becomes so vigorous that the velocity field is turbulent (for a review of this phenomenon written for an general audience of physicists, please see a recent article in the open-access journal Physics). Turbulent convection is an important process in many respects. It occurs naturally in the Earth's atmosphere and oceans and thus has short-term as well as long-term impact on climate and weather. It occurs in the Earth's mantle and contributes to the motion of continental plates and to vulcanism. In the outer core of the Earth it determines the magnetic field in which we live. It is the important heat-transport mechanism in an outer layer of the Sun and thus affects the temperature of our environment. It plays a significant role in many industrial processes, where its enhancement or inhibition may have significant economic consequences. It is a common phenomenon in everyday life which provokes fascination for the non-specialist.
In order to make progress toward understanding complex phenomena such as those mentioned above, idealized laboratory systems often are used because they permit quantitative experimental studies of specific aspects of the problem. We study this turbulent state under quantitatively controlled laboratory conditions at temperature gradients which exceed the one at onset by factors from ten thousand up to a billion. Our main emphasis has been on turbulent heat transport measurements, on studies of thermal boundary layers near the top and bottom confining plates, and on investigations of large-scale flows in this system. If you are interested in learning more about this topic, you can look at a talk given on March 30 2000 at the KITP or at a more recent talk given on April 13 2005 at the Center for Interdisciplinary Research in Fluid Mechanics. For selected recent publications, see 225, 227, 228, , 238, 245, 247, 249, 250, 251, 252, 259, 262.
Some recent Talks by our group:
Les Houches talk by Denis Funfschilling on Jan. 26 2010 (18 MB).
Invited Talk in Marburg, Germany by Guenter Ahlers on May. 28 2010 (61 MB).
Invited Talk at Haverford College ("Gollub Fest") by Guenter Ahlers on May 19 2011 (90 MB).
Plenary Talk at Virginia Tech. by Guenter Ahlers on Nov. 3 2011 (90 MB).
SFB963 Seminar by Guenter Ahlers on May 4 2012 (90 MB).
Keynote lecture at the Hong Kong RBC conference by Guenter Ahlers on Dec 10 2012 (30 MB).
Pattern-forming nonlinear systems
Characteristic of this work is the acquisition and analysis of images of flow
patterns in fluid-mechanical systems. The central part of the logo shown above
is a particularly beautiful example. It is a convection pattern obtained by
Kristina Lerman in a thin
horizontal layer of an ethanol-water mixture heated from below, and consists
of a travelling wave of convection rolls just inside of the circular sidewall
of the cell. If you would like to see more beautiful pictures of convection
patterns, please go to our
Picture Page. In recent years the emphasis of much of our work in this area has shifted to the study of the effect of thermal noise on pattern-formation phenomena. If you are interested in learning more about this topic, you can look at recent talks (talk1,talk2). For selected recent publications, see 233, 234, 241 , 242, 243, 246, 248, 255, 257, 256, 258, 261.
For a talk about the "Legacy of Henri Benard and Lord Rayleigh", see legacy_talk.
For a broad overview of Rayleigh-Benard convection, see the "2007 Otto Laporte Lecture".
See the pictures of our GROUP PICNIC of March 8 2003 !!! (small htm version)
See the pictures of our GROUP PICNIC of March 8 2003 !!! (large better quality pdf version)
See the pictures of the Leiden Euromech RB turbulence meeting (June 2003) !!! (small htm version)
See the pictures of the Leiden Euromech RB turbulence meeting (June 2003) !!! (large better quality pdf version)
See the pictures of our recent (7-27-06) group picnic !!! (small htm version)
See the pictures of our recent (7-27-06) group picnic !!! (large better quality pdf version)
See the pictures of the Boltzmann memorial dedication on Sep. 4 2006, and the Trieste RB Turbulence meeting Sep. 4 to 8 2006 !!! (small htm version)
See the pictures of the Boltzmann memorial dedication on Sep. 4 2006, and the Trieste RB Turbulence meeting Sep. 4 to 8 2006 !!! (large better quality pdf version)
Some Recent Talks
- Physics Department
- Kavli Institute for Theoretical Physics
- UC Santa Barbara
APS Topical Group on Statistical and Nonlinear Physics
- APS Home Page
Guenter Ahlers/ email@example.com