Page 36 - Fall2013

REMINISCENCES OF MIGUEL JUNGER
David Feit
Acoustical Society of America Melville, NY 11747-4502
Joel Garrelick
505 Tremont Street, Unit 209 Boston, MA 02116
Miguel C. Junger was honored be identified as propagating waves, reveal-
during the recent 165th
Meeting of the Acoustical Society of America, held in Montreal, Canada on 2-7 June, 2013, jointly with the 21st International Congress on Acoustics and the 52nd Meeting of the Canadian Acoustical Association. The memorial session afforded colleagues, friends, and family the opportunity to reminisce and share sentiments of this remarkable man.
Invited papers were given by a num- ber of his former colleagues, after his son Sebastian shared his recollections of “lessons learned” from his dad. In a moving talk, with his mother looking on with obvious pride, Sebastian remem- bered Miguel’s love of history and the beauty of science and reason, as well as the importance he placed on family and friends and being true to your values. He fondly remembered at first confus- ing, but eventually invaluable, conversa- tions with Miguel about fluid and struc- tural dynamics while writing his first book, “The Perfect Storm.”
David Feit, in his talk “Miguel C.
Junger: Legacy contribution to the field of
structural acoustics”, reviewed a number
contributions to structural acoustics, many of which appear in Miguel’s classic text “Sound Structures and Their Interaction” (MIT Press, 1972, 1986), which was coauthored with David. He noted that in earlier texts on acoustics, including Lord Rayleigh’s classic, The Theory of Sound, vibrations are treated in vacuo in the first volume and in the second volume the sound radiated by the vibrations is then considered. In contrast, here the influence of the acoustic medium on the vibration field is taken into account, earning the label “structural acoustics”. David reviewed in some detail the early applications of the Sommerfeld-Watson transformation to analyze the asymptotic high frequency response of various acoustic and structural vibration problems occurring in separable geometries that admit analytic wave har- monic solutions. For example, the point driven fluid loaded, thin cylindrical shell of infinite extent. These series, which con- verge slowly at high frequencies, are transformed into a contour integral representation that is manipulated into fast converging series of residue terms. Moreover, these terms can individually
In both style and content, and without exception, Miguel’s writings read as celebrations of discovery and understanding, and are joys to behold.
ing great insights into the physical nature of the solutions. The introduction of this technique was a major contribution to the structural acoustics community.
Joel Garrelick discussed the won- derfully insightful physical interpreta- tions that typically accompanied Miguel’s theoretical analyses. However, in his talk entitled, “Three curious results of radiation loading calcula- tions”, Joel focused on three cases where Miguel found providing such insights particularly challenging. These are:
1. At frequencies above coincidence, the power radiated by a point driven infi- nite thin plate exposed to a low impedance fluid is equal to the power radiated by that plate when submerged in a high imped- ance fluid.
2. At low frequencies, the entrained mass associated with a translating circular piston fully submerged in an acoustic medium is equal to that acting on the pis- ton when it is baffled.
3. The low frequency admittance of a fluid loaded infinite thin plate driven by a point force exhibits a spring-like reactance, and yields a phase angle magnitude that is
of Miguel’s seminal
equal to that of the plate when driven by a line force. Questions appear to remain as to whether these outcomes are paradoxical, coincidental, or merely remain to be explained.
Tom Geers reflected on the extraordinarily broad range of Miguel’s contributions to science and engineering. This includ- ed the field of bubble acoustics, which became of particular interest to Tom, and accordingly was the subject of his presenta- tion on “Reduced models for violent bubble collapse”. Following Miguel’s love for the history of science, Tom traced the develop- ment of analytical bubble dynamic models over the last century or so, from early lumped parameter representations to finite dif- ference solutions of the Euler equations, accounting for the internal gas and the occurrence of shock waves.
Rudolph Martinez, in his paper, “Poisson coupling in the in vacuo dynamics of an Infinite cylindrical shell”, revisited the axisymmetric in vacuo dynamics of a thin cylindrical shell. Starting with the equations of motion as given in, “Sound, Structures and their Interaction”, Rudolph described a perturbation analysis for the cross-coupling between in plane
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