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Brooke Benjamin
Times obituary
T. Brooke Benjamin, FRS, Sedleian Professor of Natural Philosophy at the University of Oxford since 1979, died from cancer on August 16, aged 66. He was born on April 15, 1929.
An engineer by early training, Brooke Benjamin was a major figure in postwar hydrodynamics. He made discoveries of fundamental importance in the study of water waves, internal gravity waves, cavitation and bubble dynamics in liquids, and vortex breakdown in aerodynamics. His work had wide practical implications over a range of problems experienced in high-speed flight and in movement through water. Among other things, Benjamin demonstrated how the collapse of bubbles in water could cause erosion of ships' hulls and propellers, and how thin vortices on aircraft wings could suddenly behave like shock waves.
His career was marked by a progression toward abstraction in the application of mathematical techniques to physical problems. But he retained a profound awareness of the importance of experiment in conjunction with rigorous theoretical argument, and his work was characterized by a rare combination of skills in both of these avenues of research.
Through his efforts over four decades, Benjamin ensured that British research on gravity-wave motion in all its aspects, outstanding since the pioneering era of Kelvin, Rayleigh, and Horace Lamb, remained exceptionally strong in relation to world activity in the field. He inspired successive generations of graduate students, a number of whom themselves now hold chairs in applied mathematics at British universities.
The son of a Liverpool solicitor, Thomas Brooke Benjamin was educated at Wallasey Grammar School. His schooling was disrupted by the onset of diabetes at the age of 14, but he gained admission to Liverpool University to study electrical engineering, graduating with a BEng in 1950.
After receiving his master's degree at Yale on a Rotary Foundation scholarship, he went to the Cambridge University engineering department to research under A. M. Binnie the problem of cavitation in liquids, that is, the mechanism by which cavities or bubbles may spontaneously appear in liquids at low pressure, and the manner of their subsequent collapse. Benjamin's PhD thesis on this subject set the pattern for the style of research that he was to develop to great effect through the 1960s: an elegant and thorough theoretical discussion of the problem, followed by an experiment of highly original design that demonstrated with great simplicity and impacted the validity of the foregoing theory.
Previous work on cavitation had been hampered by the fact that, as for example in the wake of a propeller, bubbles tend to appear in large numbers, and it is difficult, if not impossible, to follow the life cycle of one of them. Benjamin devised a method by which a single bubble could be created repeatedly, each such bubble collapsing and disappearing in less than 1/30th of a second. By using a stroboscope tuned to the same frequency as that of the bubble-creation mechanism, he was able to follow the life cycle of a collapsing bubble in detail. The work was a scientific masterpiece and was the foundation for later work (with A. T. Ellis in 1966) in which he showed that the effect of a nearby solid boundary is to generate a very destructive jet impacting on the boundary and causing erosion..
In 1954, while still a research student, Benjamin published his first paper in collaboration with M. J. (now Sir James) Lighthill, which was concerned with the energy and momentum of periodic waves of finite amplitude. This had important implications for the understanding of the Severn bore and similar natural phenomena.
Destined to become a classic in the field, this paper defined a theme to which Benjamin frequently returned. Indeed, in his last paper, published just three weeks before his death, a conjecture in the original theory was finally vindicated, an astonishing culmination of four decades of reflection on the problem.
In 1955, Benjamin was elected a Fellow of King's College, Cambridge, and subsequently became assistant director in research in fluid mechanics. The next fifteen years were a fruitful period, during which he worked on the instability of liquid film flow, the drag reduction (important for submarine technology) associated with flexible boundaries, the phenomenon of vortex breakdown (as, for example, in the leading-edge vortex formed above a delta wing at incidence), and above all the "sideband" instability (now known as Benjamin-Feir instability), which causes progressive waves in deep water to disintegrate if followed far enough downstream.
In recognition of these achievements, Benjamin was elected FRS in 1966 and Reader in Hydrodynamics at the University of Cambridge in 1967. During this period, he was responsible for directing the new fluid dynamics laboratory in the Department of Applied Mathematics and Theoretical Physics at Cambridge, where interaction between theoreticians and experimentalists was particularly encouraged.
In 1970 he moved to the University of Essex, where he set up the Fluid Mechanics Research Institute to promote interaction between mathematicians and experimentalists in advanced fluid mechanics. He was influenced during this period by the French school of functional analysis and did much to adapt new techniques to the solution of physical problems (for example, the stability of a vortex ring, or the "Taylor" instability of flow between concentric cylinders of finite length). He questioned conventional orthodoxies, and it was inevitable that his work during this period would encounter some skepticism.
During the late 1970s, Benjamin was much involved with the International Centre for Theoretical Physics in Trieste, concerned particularly with the training of young scientists from Third World countries
In 1979 he was elected to the Sedleian Chair of Natural Philosophy at Oxford and a Fellow of Queen's College. Here, particularly in collaboration with T. Mullin and other younger colleagues, he continued to promote the interaction of sophisticated theoretical argument and experimental work of ingenuity and precision. His published work extends to some sixty papers, some of which have the character of extended research monographs, published mainly in the Proceedings of the Royal Society and the Journal of Fluid Mechanics, of which he was Editor from 1961 to 1965.
Benjamin served on the Council of the Royal Society from 1978 to 1980 and again as a vice-president from 1990 to 1991. During his presidency (1989 to 1992) of the National Conference of University Professors, he was active in promoting debate on the mission of universities in the 1990s
He held a number of visiting appointments at American universities and developed a particularly close connection with Pennsylvania State University, where his former student and collaborator, the late W. G. Pritchard, had settled. A symposium to commemorate his 60th birthday was held there in 1989.
By nature, Brooke Benjamin was an exceptionally courteous man, of great sensitivity, charm, and acute intelligence, although coupled also with a certain inaccessibility. He was a gifted musician, known in his student days as one who could compose a tune to remember; while at Essex, he conducted the University Choir.
He was awarded honorary doctorates by Bath (1989), Brunel (1991), and Liverpool (1993) universities. He took particular pleasure in his election to foreign membership of the French Academy of Sciences in 1992
He is survived by his wife Natalia and their daughter, and by a son and two daughters from a previous marriage.
T. Brooke Benjamin, FRS, Sedleian Professor of Natural Philosophy at the University of Oxford since 1979, died from cancer on August 16, aged 66. He was born on April 15, 1929.
An engineer by early training, Brooke Benjamin was a major figure in postwar hydrodynamics. He made discoveries of fundamental importance in the study of water waves, internal gravity waves, cavitation and bubble dynamics in liquids, and vortex breakdown in aerodynamics. His work had wide practical implications over a range of problems experienced in high-speed flight and in movement through water. Among other things, Benjamin demonstrated how the collapse of bubbles in water could cause erosion of ships' hulls and propellers, and how thin vortices on aircraft wings could suddenly behave like shock waves.
His career was marked by a progression toward abstraction in the application of mathematical techniques to physical problems. But he retained a profound awareness of the importance of experiment in conjunction with rigorous theoretical argument, and his work was characterized by a rare combination of skills in both of these avenues of research.
Through his efforts over four decades, Benjamin ensured that British research on gravity-wave motion in all its aspects, outstanding since the pioneering era of Kelvin, Rayleigh, and Horace Lamb, remained exceptionally strong in relation to world activity in the field. He inspired successive generations of graduate students, a number of whom themselves now hold chairs in applied mathematics at British universities.
The son of a Liverpool solicitor, Thomas Brooke Benjamin was educated at Wallasey Grammar School. His schooling was disrupted by the onset of diabetes at the age of 14, but he gained admission to Liverpool University to study electrical engineering, graduating with a BEng in 1950.
After receiving his master's degree at Yale on a Rotary Foundation scholarship, he went to the Cambridge University engineering department to research under A. M. Binnie the problem of cavitation in liquids, that is, the mechanism by which cavities or bubbles may spontaneously appear in liquids at low pressure, and the manner of their subsequent collapse. Benjamin's PhD thesis on this subject set the pattern for the style of research that he was to develop to great effect through the 1960s: an elegant and thorough theoretical discussion of the problem, followed by an experiment of highly original design that demonstrated with great simplicity and impacted the validity of the foregoing theory.
Previous work on cavitation had been hampered by the fact that, as for example in the wake of a propeller, bubbles tend to appear in large numbers, and it is difficult, if not impossible, to follow the life cycle of one of them. Benjamin devised a method by which a single bubble could be created repeatedly, each such bubble collapsing and disappearing in less than 1/30th of a second. By using a stroboscope tuned to the same frequency as that of the bubble-creation mechanism, he was able to follow the life cycle of a collapsing bubble in detail. The work was a scientific masterpiece and was the foundation for later work (with A. T. Ellis in 1966) in which he showed that the effect of a nearby solid boundary is to generate a very destructive jet impacting on the boundary and causing erosion..
In 1954, while still a research student, Benjamin published his first paper in collaboration with M. J. (now Sir James) Lighthill, which was concerned with the energy and momentum of periodic waves of finite amplitude. This had important implications for the understanding of the Severn bore and similar natural phenomena.
Destined to become a classic in the field, this paper defined a theme to which Benjamin frequently returned. Indeed, in his last paper, published just three weeks before his death, a conjecture in the original theory was finally vindicated, an astonishing culmination of four decades of reflection on the problem.
In 1955, Benjamin was elected a Fellow of King's College, Cambridge, and subsequently became assistant director in research in fluid mechanics. The next fifteen years were a fruitful period, during which he worked on the instability of liquid film flow, the drag reduction (important for submarine technology) associated with flexible boundaries, the phenomenon of vortex breakdown (as, for example, in the leading-edge vortex formed above a delta wing at incidence), and above all the "sideband" instability (now known as Benjamin-Feir instability), which causes progressive waves in deep water to disintegrate if followed far enough downstream.
In recognition of these achievements, Benjamin was elected FRS in 1966 and Reader in Hydrodynamics at the University of Cambridge in 1967. During this period, he was responsible for directing the new fluid dynamics laboratory in the Department of Applied Mathematics and Theoretical Physics at Cambridge, where interaction between theoreticians and experimentalists was particularly encouraged.
In 1970 he moved to the University of Essex, where he set up the Fluid Mechanics Research Institute to promote interaction between mathematicians and experimentalists in advanced fluid mechanics. He was influenced during this period by the French school of functional analysis and did much to adapt new techniques to the solution of physical problems (for example, the stability of a vortex ring, or the "Taylor" instability of flow between concentric cylinders of finite length). He questioned conventional orthodoxies, and it was inevitable that his work during this period would encounter some skepticism.
During the late 1970s, Benjamin was much involved with the International Centre for Theoretical Physics in Trieste, concerned particularly with the training of young scientists from Third World countries
In 1979 he was elected to the Sedleian Chair of Natural Philosophy at Oxford and a Fellow of Queen's College. Here, particularly in collaboration with T. Mullin and other younger colleagues, he continued to promote the interaction of sophisticated theoretical argument and experimental work of ingenuity and precision. His published work extends to some sixty papers, some of which have the character of extended research monographs, published mainly in the Proceedings of the Royal Society and the Journal of Fluid Mechanics, of which he was Editor from 1961 to 1965.
Benjamin served on the Council of the Royal Society from 1978 to 1980 and again as a vice-president from 1990 to 1991. During his presidency (1989 to 1992) of the National Conference of University Professors, he was active in promoting debate on the mission of universities in the 1990s
He held a number of visiting appointments at American universities and developed a particularly close connection with Pennsylvania State University, where his former student and collaborator, the late W. G. Pritchard, had settled. A symposium to commemorate his 60th birthday was held there in 1989.
By nature, Brooke Benjamin was an exceptionally courteous man, of great sensitivity, charm, and acute intelligence, although coupled also with a certain inaccessibility. He was a gifted musician, known in his student days as one who could compose a tune to remember; while at Essex, he conducted the University Choir.
He was awarded honorary doctorates by Bath (1989), Brunel (1991), and Liverpool (1993) universities. He took particular pleasure in his election to foreign membership of the French Academy of Sciences in 1992
He is survived by his wife Natalia and their daughter, and by a son and two daughters from a previous marriage.
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