Owen Martin Phillips, a pioneer in geophysical fluid dynamics who devised a leading theory for the generation of ocean waves by the wind, died at home of gastric cancer on 13 October 2010 in Chestertown, Maryland.
Phillips was born on 30 December 1930 in Parramatta, New South Wales, Australia. He graduated from the University of Sydney with a BSc degree in applied mathematics in 1952. That same year he moved to the UK to begin graduate research at Cambridge University, initially under the supervision of G. I. Taylor and later under George Batchelor.
Phillips’s 1955 PhD thesis, “On Shear Flow Turbulence,” exemplified the Cambridge approach to turbulence and earned him a postdoctoral fellowship at St. John’s College, where he began seminal research on ocean-wave generation by the wind. At that time, existing theories for ocean-wave generation assumed laminar flow at the air–sea interface and grossly underpredicted the actual rate at which ocean waves grow. Adapting statistical theories of homogeneous turbulence recently developed by Andrei Kolmogorov, Batchelor, and others to the air–sea interface, Phillips demonstrated how turbulent pressure fluctuations in the wind resonate with propagating ocean waves. Back-to-back 1957 volumes of the Journal of Fluid Mechanics contain Phillips’s turbulence paper and another by John Miles proposing a critical layer-growth mechanism; together they provided a theoretical basis for decades of ocean-wave measurements.
Phillips first came to the US in 1957 as an assistant professor in mechanical engineering at the Johns Hopkins University. Apart from a brief return to Cambridge to join the newly formed department of applied mathematics and theoretical physics, Phillips would spend the rest of his career at Johns Hopkins, as an associate professor beginning in 1960 and as a full professor from 1963 on.
In the 1960s the nonlinear interaction among gravity waves had become the major stumbling block for theories of the statistical properties of the ocean surface. In a series of papers between 1958 and 1962, Phillips developed what became the standard model for the equilibrium range in the spectrum of wind-generated waves. Phillips’s influential 1966 monograph, The Dynamics of the Upper Ocean (Cambridge University Press), provided the theoretical framework connecting ocean variability to waves and turbulence.
His research on ocean-wave mechanics found many practical applications. For example, he demonstrated that the height of so-called rogue waves—giant ocean swells that occasionally arise from random interactions of smaller waves and are known to capsize large ships and ocean platforms—can be predicted using routine measurements from monitoring buoys. Somewhat inadvertently, he also developed a method of submarine detection based on the modulation of surface waves by the internal waves generated as the submarine moves through the ocean thermocline.
Phillips then turned his attention to problems in geophysical turbulence. Between 1968 and 1978, he carried out a series of landmark experiments with H. Kato, Lakshmi Kantha, and others, in which they measured the rate of turbulent entrainment in a stratified fluid as a function of the stress applied at the fluid’s surface. Those experiments yielded the first scaling laws directly applicable to wind-induced turbulent mixing in the upper ocean and in the atmosphere boundary layer, both critical processes for the regulation of Earth’s climate.
Phillips had a gift for communicating science to audiences at all levels. His 1968 book The Heart of the Earth (Freeman, Cooper and Co), a highly original introduction to geophysics, is singular in its emphasis on the use of scientific inference and dimensional analysis in the exploration of Earth’s and other planets’ interiors. As global energy crises struck in the 1970s, Phillips became alarmed by how lightly Americans were treating an important issue that directly affected their security. His whimsically titled The Last Chance Energy Book (Johns Hopkins University Press), published in 1979, gives a lively, prescient account of the true costs and risks of our energy negligence. His leadership in the Maryland Academy of Sciences in the 1970s marked a period of extraordinary expansion of its public outreach.
The next chapter in Phillips’s research career began in the late 1980s when he collaborated with several geology colleagues on problems of how aqueous fluids infiltrate and react with permeable sedimentary and metamorphic rocks. In his 1991 monograph Flow and Reactions in Permeable Rocks and in Geological Fluid Dynamics: Sub-surface Flow and Reactions (both from Cambridge University Press) published in 2009, Phillips developed fluid mechanical theories for isothermal reaction fronts and for gradient reactions controlled by temperature variations in rock; both are important processes in hydrothermal systems.
Although he was humbly aware of his own limitations, Phillips saw little value in propping up the walls between scientific disciplines; indeed, he spent his career forging links between seemingly disparate fields. And he knew well the role played by good fortune when he told the Johns Hopkins Gazette in 1998,
In doing science, everybody has a number of strokes of luck, and some people miss them. When you see that an opportunity is given, you must grab it. Now, the luck brings it along, but you have to have the awareness to take advantage of it.
Many scientists he inspired around the world might add that their own best stroke of luck was to have known Owen Phillips.