Julian Hunt, who was a member of the DAMTP academic staff from 1970 to 1992, first as a Lecturer – a joint appointment with Engineering – then as Reader and subsequently Professor in Fluid Mechanics, has died aged 84.
Julian was educated at Westminster School. He was a scholar at Trinity College, Cambridge where he obtained a First Class Honours Degree in Mechanical Sciences (now part of the Engineering Tripos) in 1963 and was awarded his PhD on Aspects of Magnetohydrodynamics under the supervision of Arthur Shercliff in 1967. He was elected to a Fellowship at Trinity in 1966. After a year as a visiting lecturer in South Africa and as a Fulbright Scholar in the USA in 1967, he spent two years as a Research Officer with the Central Electricity Generating Board (CEGB). Julian returned to Cambridge in 1970 to take up a Lectureship in Applied Mathematics and Engineering. He was Reader in Fluid Mechanics from 1978 to 1990 and a Professor from 1990 to 1992, when he was appointed Director-General and Chief Executive of the Meteorological Office. After his retirement from the Meteorological Office in 1997, he joined the Department of Earth Sciences at University College London as Professor of Climate Modelling. Julian was created a Baron in the House of Lords in 2000 with the title Lord Hunt of Chesterton. (He had represented Chesterton as a Cambridge City Councillor and was Leader of the Labour group of on the Council.)
Julian was much involved in the Institute of Mathematics and its Applications, becoming Vice-President in 1989-1993 and President from 1993-1996. He was the founding Secretary-General of the European Research Community for Flow, Turbulence and Combustion (ERCOFTAC) in 1988. He was elected a Fellow of the Royal Society in 1989 and was awarded the L.F. Richardson Prize of the European Geophysical Society in 2001.
While at CEGB Julian focused on aerodynamic problems arising from the disaster at the Ferrybridge cooling towers, three of which had collapsed under high winds in November 1965. This work led Julian to an extended development of so-called 'rapid distortion theory', initially developed by George Batchelor, applicable whenever a turbulent wind is distorted by any large obstruction in its path (e.g. a building complex or a group of skyscrapers). It applies equally to wind flow over hilly terrain, and where density stratification and other atmospheric effects come into play.
Always interested in practical problems, Julian along with colleagues founded Cambridge Environmental Research Consultants in 1985 and he was instrumental in developing one of their major software products, the Atmospheric Dispersion Modelling System (ADMS), that initially provided estimates of downwind pollution concentrations from industrial stacks. ADMS was subsequently developed as a complete urban modelling system for predicting pollution from vehicle and other urban emissions, and is currently used by many cities throughout the world.
After his retirement Julian was an active member of the House of Lords who made many contributions to discussion and committee work, particularly with regard to science, the environment and energy. He became an enthusiastic advocate for STEP (the Spherical Tokamak for Energy Production) which involves magnetic containment of plasma in a spherical geometry. The severe engineering problems in realising this project, which is a central ingredient of UK energy strategy, involve the sort of MHD for which Julian's extended experience was highly relevant.
Julian's scientific investigations were characterised by great flair and originality, bold assumptions, and deep physical intuition, enabling him to make progress in the ever-challenging field of turbulence, in both meteorology and ground-based engineering projects of great practical importance. He was a warm and supportive mentor to his students and junior colleagues and to his many collaborators from around the world.
Julian is survived by Marylla, who he married in 1965, and their three children, Jemima, Matilda and Tristram, and eight grandchildren.