In Memoriam: Emmanuel Partheniades

Emmanuel Partheniades, recognized by all in the know about the scour of clayey sediment beds by flowing water, passed on October 31, 2019 in Gainesville, Florida, just short of his ninety-third birthday. As one of the only two students of Professor Hans Albert Einstein at University of California, Berkeley (UC Berkeley), who worked on the physics of movement of flocculated fine-grained particles, Partheniades and the other student, the late Ray B. Krone, were pioneers in the US in introducing phenomenological interpretations of the mechanics of cohesive sediment transport, until then mainly reliant on empirical formulations.

At the time of his death a professor emeritus at the University of Florida, Partheniades was born in Athens, Greece on November 3, 1926. During his teen years his education was interrupted by the war in Europe, and he finally received his undergraduate degree in civil engineering at the age of 25 from the Technical University of Athens in 1952. This was followed by Masters (1955) and Ph.D. (1962) degrees, both in civil engineering, from UC Berkeley. From 1952 to 1954, and again during 1955–1959, he worked in structures, irrigation, and soil mechanics with various engineering firms in Greece, and in the San Francisco Bay area including Dames and Moore. That experience convinced him that academics was his calling; he never again worked or consulted on engineering projects outside university-based research.

His first teaching assignment was at Cal State San Jose in 1963, and in 1964 he went to Massachusetts Institute of Technology (MIT) as a postdoctoral fellow under Professor John F. Kennedy in civil engineering. Following a professorial position at the State University of New York in 1966, he joined University of Florida in 1968 as professor in the Department of Coastal and Oceanographic Engineering. After a 10-year hiatus (1973–1983) during which he returned to Greece as Chair of Hydraulic Structures at the University of Thessaloniki, he returned to University of Florida, this time joining the Department of Engineering Sciences, later renamed Aerospace and Mechanical Engineering. In the US he was a member of ASCE and served as an academic consultant and lecturer in, among other countries, Venezuela, Paraguay, Argentina, Portugal, India, and Canada.

Partheniades was fond of European history, especially the war years, and was passionate about operas and classical music in general. A purist, even in the age of YouTube, he preferred to listen to his own vintage records of arias by famous sopranos. He met his Peruvian wife Dora Gutierrez, who shared many of his interests, while he was a student at UC Berkeley and she, also a Berkeley graduate, was employed on the campus. He was deeply devoted to her and to his faith, and was active in the Greek community of Gainesville. He greatly enjoyed traveling and narrating his experiences to his friends and colleagues. Following his wife’s death 2014 he withdrew from most academic interests and limited his travel shuttling between his home in Gainesville and one in Thessaloniki, which commanded a view of Mount Olympus. He left behind his elder sister in Athens as the only close survivor.

Partheniades’ most noteworthy contribution to cohesive sediment transport was his journal article in 1965 on the erosion of soft beds of flocculated mud collected from San Francisco Bay. He prepared two types of beds in a hydraulic flume, one consisting of natural well-mixed mud placed on the flume bottom and another prepared by depositing suspended mud. As a result of these procedures the cohesive resistance of the placed bed to erosion was independent of depth within the bed whereas that of the deposited bed increased with depth. Under turbulent flow it was found that the erosion flux at the surface of the placed bed remained independent of time, while that of the deposited bed decreased until almost no erosion occurred after several hours. From these observations he concluded that unlike in the case of a sand bed subjected to steady flow, at the surface of which erosion and deposition fluxes quickly become equal after the onset of a test, when a cohesive bed erodes no redeposition occurs regardless of the method of bed preparation. According to him this behavior could be explained by reinterpreting one part of Einstein’s stochastic development of the well-known bedload function describing erosion only, while discarding the other part representing deposition.

The 1965 summary article was somewhat unusually published with Partheniades as the sole author as, according to his own narrative, Einstein withheld his approval to be include as a coauthor because he firmly believed that somehow deposition had to be included in the analysis. Subsequent works on cohesive sediment erosion have revealed that both Partheniades and Einstein had gotten some assumptions in the assessment of erosion right while others were contradictory. As it turns out cohesive sediment transport cannot be described without considering the dynamics of floc growth and breakup of depositing and eroding flocs, and erosion is a more complex phenomenon than captured in the Partheniades formula.

The 1965 formula did not receive as much recognition as it deserved. Instead, about a decade later a linear, empirical version named the Partheniades equation by a student of Krone became well-known because it was simple to use even though it had little theoretical underpinning. While lively and even humorous in company, Partheniades could be feisty and judgmental about his academic beliefs, and was wont to object to anyone misrepresenting anything related to his work. However, once he came to know that an erosion formula, even though quite different from his own physics-based equation, was named after him, he remained reticent about whether he had any contributive share in the development of the eponymous formula.

His first 5-year stay at the University of Florida was also the most productive period during which he introduced and taught a sequence of three graduate courses on estuarine transport processes and constructed a wind flume as well as an annular rotating flume meant to study cohesive sediment deposition in water. This latter flume was a larger version of a similar apparatus built earlier at the Parsons Lab at MIT, a brainchild of Professor Kennedy with input from Partheniades. Its somewhat complex design and operating procedure were meant to avoid the problem in typical flow-recirculating flumes in which suspended flocs reaching the downstream end of the flume are chewed up by high shear rates in the return flow pump. The Florida version was peculiar in the sense that its use required students to climb up a ladder with a platform that looked a bit like one used to get into a small aircraft. This nuance came about as follows. As part of instructions to the lab machinist, Partheniades handed the design blueprint of the MIT annular flume, indicating that it had to be doubled in size. As it wasn’t clear what that meant the machinist doubled all the dimensions including the height of the metal framework supporting the flume. Within years such flumes appeared elsewhere, especially in the Far East, that were nearly identical copies also designed with similar ladders, perhaps because it was thought that there was some underlying scientific purpose. As the MIT flume was soon demolished, the one in Florida became the Model-T that was replicated in several other countries with suitable modifications and sophisticated instrumentation for operation and measurement. It also found popular application in studies involving mud with biota.

At the University of Florida, Partheniades guided two doctoral theses, one in estuarine cohesive sediment transport and another in salinity intrusion, and in 2009 published a monograph summarizing his lifelong work. Conservative in thinking, harking back on science as practiced until about mid-twentieth century, he was a champion of basic laboratory work but remained apprehensive about field work and especially numerical modeling as a research tool. After his return to Gainesville in 1983 he largely eschewed experimental work in favor of teaching statics, dynamics, and fluid mechanics. His decades of professional tenure coincided with the growth of cohesive sediment transport as a major subarea of hydraulics.