Gilles Marc Corcos

A visiting speaker from the University of Chicago described Gilles Corcos as being “not only a fine researcher, but a decent human being, a combination rarer than you may think.” After receiving his Ph.D. in Aerospace Engineering from the University of Michigan in 1953, Corcos held a post-doctoral fellowship with Francis Clauser at The Johns Hopkins University from 1952-1954. He worked at the Douglas Aircraft Corporation, then in 1958 joined the Department of Mechanical Engineering at Berkeley as Assistant Professor.

During his career, Corcos interacted fruitfully with many graduate students from this and other departments at Berkeley. One doctoral student wrote his thesis on a problem in turbulent flow, then went on to pioneer the application of mechanics to planetary interiors and atmospheres, and to membership of the NAS. Corcos took early retirement from the university as Professor in 1990.

Gilles Corcos was recognized internationally for his work on hydrodynamic stability and turbulence. He published relatively few papers, with final publication in an archival journal preceded by one or more technical reports published as his thoughts matured. The resulting papers are well thought out, and clearly argued; he described colleagues who published minor calculations made along the way to understanding as having “published their ‘homework.’”

One series of reports led to two papers in which Corcos analyses how finite size of a pressure- measuring device, such a microphone, affects the resolution of different frequencies in a pressure signal generated by turbulent flow. This is the problem of extracting a sonar signal from the pressure fluctuations in the shear flow along the hull of a boat; it is also that of separating the words of a speaker addressing a crowd outdoors from the noise of the wind. His analysis has been cited at roughly constant rate over the six decades since its publication. Because the analysis has found a wide range of applications, the phrase "Corcos model" enters into the titles and abstracts of papers.

Another series of papers published between 1976 and 1984 treated the “mixing layer" which forms between two layers of fluid moving at different velocities. In the 1970s it became apparent that although turbulent shear flow appears to vary randomly in time when observed at a fixed point, pictures of the entire flow at a given instant show the presence of large-scale organized structures (Milton Van Dyke, "Album of Fluid Motion," plate 176).

Motions at several smaller scales are imbedded within these large structures; the shear drives the turbulence by performing work on the large structures, and the energy so provided is eventually converted to heat at the smallest scales of the motion. Based on the observation of large-scale structures in the mixing layer, Corcos proposed a model of how energy was transferred from the largest scales to the smallest scales in three stages. He analyzed in detail the first two stages using a combination of computation and experiment, then developed a simplified model to interpret the results. The third stage proved more difficult to treat, and its analysis was not completed. This importance of this work was recognized by his election in 1984 as a Fellow of the American Physical Society “for his theoretical, numerical and experimental contributions to the study of the stability of and turbulence in sheared and stratified flows” (description from the APS website).

From 1986, Corcos served as Chairman of the Board and Director of DiCon Fiberoptics. There, he also served as Chief Financial Officer; among other things, he helped the company survive predation by a much larger firm which later went bankrupt. In 2024, DiCon is flourishing.

In 1987, Corcos and others cofounded Agua Para La Vida (APLV), a non-profit organization to provide potable water and sanitation in rural Nicaragua. As of 2024, ALPV has cooperated with over one hundred communities to build supply systems, improve sanitation, protect watersheds and provide health and hygiene education. To make this process self-sustaining, in 1996 Corcos helped found an accredited technical school in Rio Blanco Nicaragua to train rural youth in all aspects of design, construction and maintenance of drinking water and sanitation systems.

The communities to be served consist of subsistence farmers occupying widely dispersed houses and farming their own small plots by hand. The supply systems must be designed taking into account that the communities seldom have electric power, or access to capital. Providing potable water entails finding a clean spring, and creating a piping system through which water will flow without mechanical pumps to widely dispersed houses. Because the pipeline must run over local elevations, and have branches and faucets along the way, careful design is required to ensure that air does not accumulate at a high point and prevent flow further downstream. Corcos analyzed this problem, and presented his solution as a practical manual allowing the design to be performed in simple steps (“Air in Water Pipes,” published by APLV in both Spanish and in English). In the forward to it, he wrote that "several classes of Engineering Seniors chose this very topic for their senior laboratory class and contributed useful data"; he continued to educate himself and in doing so, educated his students.

Because the houses are widely dispersed and located at different elevations below the spring, the system must be constructed in such a way that when a faucet is opened in one of the uppermost houses, lower houses are still supplied. Ensuring that water flows on demand when any of these faucets is opened at random leads to a problem in optimal design. Corcos collaborated with colleagues in Europe and Latin America to develop the algorithm and computer program needed to solve it. In 2015, this work was recognized by an award to APLV from the International Development Bank. It also led to his final publication (F. Babonneau, G. M. Corcos, L. Drouet and J.-P. Vial, NeatWork: A Tool for the Design of Gravity Driven Water Distribution Systems for Poor Rural Communities. INFORMS J. Appl. Analytics, 49, 2: 129-136 (2019)).

Gilles Corcos is survived by his brother Alain; by daughters Ana, Laura and Nadija, and their mother; by his second wife Anne Bleecker Corcos; and by the memory of his habit of whistling chamber music to himself as he walked the corridor of Etcheverry Hall.

Stephen Morris
Charlie Huizenga
John Neu