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Hydrodynamic Stability Problems. John Walton

Shortly after Bob Sprague left K.U.(late 1950's) I met another physics student, John Walton, who was searching for a Ph.D. thesis topic in hydrodynamics. In those days not very many physicists were doing their primary research in this field, and the use of the digital computer was just beginning to be felt; indeed great advances in computational-hydrodynamics would soon occur, especially at the National Laboratories, where problems associated with explosions and the structure and evolution of shock waves, etc., had to be solved. But such studies would require the development of very fast, large storage computers, and the carrying out of specialized, and on occasion, large scale experiments.

Not intimidated by such thoughts, Chandrasekhar had been working on problems of hydrodynamic stability that could be solved in the linear domain by first finding a stationary state of the fluid, and then subjecting it to small perturbations. Thus he was able to solve such problems as the thermal instability of a fluid layer heated from below, or the stability of superposed fluids. He had even established a laboratory on the University of Chicago campus for carrying out experiments in this field. In some ways this was very surprising, since he had the reputation for being a pure theorist; indeed I recall Struve once saying in jest that Chandra didn't know which end of a telescope to look into!

In any event, Chandra had been writing a very thick book titled Hydrodynamic and Hydromagnetic Stability, and it was possible for me to get him to suggest a reasonable thesis problem for Walton, viz., the problem of the stability of fluid cylinders taking the surface tension into account. Walton formulated the perturbation equations, and I worked separately to check them. He took the problem from there, derived the solution, and wrote up his preliminary manuscript which he then presented to the physicists on his thesis committee. One of them, the theoretician Daniel Ling, got very interested in the problem and devised a somewhat different approach than that usually adopted by Chandra. After about three weeks he finished deriving his equations, and they were essentially the same as those Walton had obtained. In the meantime a lady scientist from Israel published her results to the same problem. But she had not introduced any electromagnetic fields into the problem, so Walton did, amended his original solution, and was able to get a thesis out of the situation titled The Hydromagnetic Stability of Fluid Cylinders (October, 1961).

After completing his Ph.D. requirements he then interviewed at various places, and finally settled on a position at the LLNL (Lawrence Livermore National Laboratory). The first thing he was called upon to do in his new position was to participate in observing the last few nuclear explosions in the Pacific of the operation Dominic test series (1962) that terminated the U.S. participation in above-ground testing. He remained at Livermore working in the theoretical division until last year (1997), when he retired. I'm told that he and his wife have now returned to the Kansas City area.