Tony Ladd
Ph.D., 1978, University of Cambridge, Cambridge, England.
Professor : Chemical Engineering
Ph : 352-392-6509
Fax: 352 392-9513
tladd@che.ufl.edu
Faculty Web Page
Areas
Complex Fluids
Soft Matter
Transport phenomena
 
Our research focuses on the dynamics of systems at the micron scale; colloids, polymers, and other soft matter. The research combines the scientific disciplines of statistical mechanics and fluid dynamics with advanced computing to elucidate the key physical processes that underlie laboratory observations and measurements. Areas of application include statistical physics, biophysics and geophysics. An example of our work is described below.

The origin of underground cave systems, such as those at Mammoth Mountain, Kentucky (right) has been investigated for over 100 years. In the 19th century, Lyell realized that subterranean caverns were the result of dissolution by weakly acidic solutions of atmospheric CO2. However, models for the dissolution process suggest that water flowing through limestone formations is very quickly saturated with calcium ions, over distances of the order of centimeters. Nevertheless, limestone caverns extend for kilometers; Mammoth cave in Kentucky has nearly 400 miles of passages. So how does the dissolution get so deep? The answer until recently has been described in terms of changes in chemical kinetics; in natural calcite the reaction rate decreases by orders of magnitude near saturation. Paradoxically this promotes dissolution since the undersaturated solution can penetrate deeper into the fractured rock. Although this is an appealing and widely accepted resolution of the cave formation paradox, it turns out to be the wrong explanation. Recently, Piotr Szymczak and I realized that there is a universal instability in the equations for fracture dissolution, so that a dissolution front is always unstable. This provides a more effective means to promote dissolution than changes in chemical kinetics and has a profound effect on how long it takes for breakthrough (when the fracture opens along its whole length) to occur. This work was recently reported in Science News and also selected as an Editor's Choice by Science magazine.

For further details on this and other work in the group please go to our home page at http://ladd.che.ufl.edu.

 
 
Recent Publications
1. P. Szymczak and A. J. C. Ladd, “The initial stages of cave formation: Beyond the one-dimensional paradigm,” EPSL, 201:424-432, 2011.
2. R. Kekre, J. E. Butler, and A. J. C. Ladd, “Role of hydrodynamic interactions in the migration of polyelectrolytes driven by a pressure gradient and an electric field,” Phys. Rev. E 82:050803(R), 2010.
3 B. Duenweg and A. J. C. Ladd, “Lattice Boltzmann simulations of soft matter systems,” Adv. Poly. Sci. 221:89-166, 2009.doi:10.1007/12_2008_4.
4. Usta, O.B., Butler, J. and Ladd, A.J.C., “Transverse Migration of a Confined Polymer Driven by an External Force,” Phys. Rev. Lett., 98 (2007) 098301.
5. Chun, B. and Ladd, A.J.C., “Inertial Migration of Neutrally Buoyant Particles in a Square Duct: An Investigation of Multiple Equilibrium Positions,” Phys. Fluids, 18 (2006) 031704.