Bubbly Shock Propagation and the Transition to Partial Cavity Shedding
Lorenz G. Straub Award Ceremony and Distinguished Seminar
Distinguished Straub Lecturer: Dr. Steven Ceccio, ABS Professor of Marine and Offshore Design and Performance and the Department Chair of Naval Architecture and Marine Engineering at the University of Michigan
Link to Video
https://umn.webex.com/umn/ldr.php?RCID=f7c21b9d1388ac9fd2ea69ee76f4a481
Join us at the St. Anthony Falls Laboratory for the presentation of the 2014 Lorenz G. Straub Award at a ceremony and distinguished lecture on Tuesday, October 11. The program will begin at 3:30 p.m. with the presentation of the award and presentations by both our awardee and our distinguished lecturer. Learn more below!
Lorenz G. Straub Award Recipient: Hang Wang, Postdoctoral Research Fellow, University of Queensland for his 2014 dissertation titled "Turbulence and Air Entrainment in Hydraulic Jumps" completed at the University of Queensland, Australia.
Abstract:
The thesis provides a comprehensive description of the turbulent two-phase flow in hydraulic jumps based upon physical modeling. Investigated flow properties ranged from free-surface dynamics, air entrainment and transport, to characteristic turbulent scales and bubble-turbulence interactions. The spatial distributions of two-phase flow properties and turbulent scales, as well as the effects of Froude and Reynolds numbers, revealed strong coupling between physical processes of air entrainment and turbulence development. Selecting the length of hydraulic jump roller as the characteristic length scale, the two-phase flow structures can be predicted based upon a semi-analytical model, with negligible viscous scale effects in terms of air entrainment flux. The turbulence properties and flow dynamics time scales, however, are subject to scale effects and can be only accurately measured at prototype conditions. The cutting-edge knowledge of hydraulic jump and such complex turbulent multiphase flows should provide solid justification for future theoretical and numerical studies that have a long way ahead.
Distinguished Straub Lecture
Bubbly Shock Propagation and the Transition to Partial Cavity Shedding
Steven Ceccio, ABS Professor of Marine and Offshore Design and Performance and the Department Chair of Naval Architecture and Marine Engineering at the University of Michigan
Abstract:
Using time resolved X-ray densitometry, time resolved 2-D void fraction flow fields for a variety of cavitating flows are examined. Results from the cavitating flows formed at the apex of a wedge, the flow over a hydrofoil, and the flow in the wake of a cylinder are presented. In these cavities are obtained to identify the mechanisms of transition from closed partial cavities to open cavities exhibiting periodic shedding of large gas pockets. From the void fraction field measurements, two distinct types of cavity shedding mechanisms are identified: shedding associated with a re-entrant jet in the cavity closure region that produces intermittent shedding of smaller scale cavities, and large scale, periodic cloud shedding caused by the formation of a condensation shock within the high void-fraction flow in the separated region of partial cavitation. A discussion of the observed occurrence and properties of the shock wave, and its role in causing periodic shedding is presented based on the one-dimensional model of shock propagation in bubbly mixtures and the relationship between the transition to strong shedding as a function of the Mach number of the bubbly flow in the cavity.
About the Straub Award:
Lorenz G. Straub, Professor of Civil Engineering, is considered the mastermind for making the idea of a hydraulic laboratory at the University of Minnesota and the St. Anthony Falls into a reality. Serving as the primary architect, Straub oversaw the construction of the laboratory using Works Progress Administration (WPA) funding from 1936 -1938. He served as SAFL's director until his death in 1963. The Lorenz G. Straub Award was established in his memory. The award, made annually, is for the author of an especially meritorious dissertation in the area of hydraulic engineering or a closely related area. In reflection of Straub's world-wide professional activities, recipients can be from any school throughout the world, which has an appropriate graduate degree program. The award consists of a medal and an honorarium.