Other Notable Deaths


August 23, 2008


Fluid mechanics expert

Philip Geoffrey Saffman, the former Theodore von Karman Professor of Applied Mathematics and Aeronautics at California Institute of Technology and a leading expert in vortex dynamics, the study of how liquids and gases of varying densities and viscosities interact, died Sunday in Pasadena, Calif., after a long illness.

Among his best-known contributions to the field was profiling viscous fingering, which became known as the "Saffman-Taylor Instability." This refers to the process by which a low-viscosity fluid forms a finger-like projection when injected into a higher-viscosity fluid. This work was key to helping the oil industry develop the best methods to recover oil in trapped basins, where water or steam must be injected to force the oil to the surface.

Dr. Saffman also made major contributions to the understanding of vorticity, which is the way ships and airplanes move through water and air. In particular, he developed a precise mathematical understanding of wake turbulence caused by jets during takeoff. That analysis helped uncover the conditions that contributed to several aircraft accidents, including a August 1985 Delta Airlines crash in Dallas, when the flight crew tried to land in a thunderstorm.

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