Seminars

Joint ME/IE 8773-8774 Seminar

Water Detrainment Across Settling Interfaces:
A New Horizon in the Modeling of Reservoir Sedimentation

by

Gary Parker , Professor, Civil Engineering
St. Anthony Falls Laboratory
University of Minnesota
Minneapolis, MN 55455

Wednesday, October 13, 2004
3:30-5:00 p.m.
Room 3-180 EE/CSci
Coffee and cookies will be available at 3:15 p.m. in room 3-176 EE/CSci before and after the seminar

Abstract:

While recent years have been characterized by rapid progress in many areas environmental fluid mechanics, the area of reservoir sedimentation is not one of them. Although increasing rates of reservoir sedimentation are causing major re-evaluations of the usefulness of dams, including considerations of dam removal, the technology for predicting sediment deposition in reservoirs remains stuck in the era of the empirical Brune trap efficiency curve. Sediment is deposited in reservoirs by fluvial deposition on the delta topset, avalanching on the delta foreset and by either plunging turbidity currents or rain from surface plumes in the bottomset. In many reservoirs the bulk of sedimentation is on the bottomset and consists of the finer sizes delivered by the river. It is this process that has proven most difficult to predict. Recent research in deep-sea sedimentation, however, offers a new concept with which to study the process. Plunging turbidity currents in reservoirs readily form muddy ponds below relatively sediment-free water. The interface between the muddy pond and sediment-free water above devolves into a settling interface, across which turbulence is damped by strong flow stratification. This interface is in many ways analogous to the meteorological interface that forms under conditions of atmospheric inversion. It differs from the atmospheric case, however, in that the agent of stratification is sediment, which falls under its own weight. In the absence of supply of sediment-laden water from upstream, the settling interface moves downward with the fall velocity of the sediment, so converting muddy water to clear water. In the presence of supply from upstream, the position of the interface can stabilize, with continuous detrainment of water across it. The position of this interface relative to the level from which water is vented from the reservoir controls the trap efficiency of the finer sediment entering the reservoir.

BIO — Professor Gary Parker joined the faculty of the University of Minnesota Department of Civil Engineering after receiving his Ph.D. from the same Department in 1974. Since 1985 he has been Professor at the St. Anthony Falls Laboratory, which he directed from 1995 to 1999. His research interests include river mechanics and morphology, river engineering, mechanics of two-phase solid-fluid flow, turbidity currents, oceanic sedimentation and submarine debris flows. He has published numerous refereed journal articles, two book chapters and an electronic book. Among the many awards that Professor Parker has received are the G.K. Warren Award from the National Academy of Sciences, the Hans Albert Einstein Award and the Huber Research Prize from the ASCE, and several best paper awards. He is a Fellow of the American Geophysical Union, an Institute of Technology Distinguished Professor, and has received the University of Minnesota Institute of Technology Outstanding Teacher Award.

Informal Faculty Luncheon: Wednesday, October 13, 2004, 12:00 noon. Meet in 1100 ME and walk to lunch with other faculty. Prof. Gary Parker will be able to attend.