土木工程与力学学院暨西部灾害与环境力学教育部重点实验室学术报告——Dr.GregoryLawrence教授

　　应土木工程与力学学院、西部灾害与环境力学教育部重点实验室邀请，THE UNIVERSITY OF BRITISH COLUMBIA Dr. Gregory Lawrence教授于2018年7月16-23日来我校进行学术交流并做学术报告，欢迎广大师生参加。

 

 

 

Shear instabilities are an important cause of turbulence and mixing in geophysical fluid flows.  In many circumstances the destabilising effect of shear is in competition with the stabilising effect of buoyancy caused by density stratification.  Results of studies of density stratified shear flows in nature, in the laboratory, and using direct numerical simulation (DNS) will be presented.  The focus will be on the importance the relative position and shape of the vertical velocity profile with respect to a sharp density interface.  If velocity profile is sharp and aligned vertically with the density interface the Kelvin-Helmoltz instability evolves; if the velocity profile is diffuse and aligned with the density interface the symmetric Holmboe instability evolves; if the velocity profile is diffuse and displaced vertically from the density interface the asymmetric Holmboe instability evolves.  The evolution of these instabilities and the degree of mixing that they cause will be explored.

 

In many parts of the world the overall water quality in lakes and reservoirs is deteriorating to the point where economic systems and human health are impaired.  The scope of these problems and the methods employed in attempts to overcome them are many and varied.  I will attempt to describe an eclectic mix of remediation strategies for lakes located primarily in Canada.  Examples that I will address include: the oxygenation of the north basin of Amisk Lake, together with an explanation of the unexpected “leakage” into the south basin; the design of a diffuser to inject supersaturated water from a Speece Cone into the hypolimnion of Newman Lake; the rapid artificial circulation of Colomac Zone 2 Pit-lake to remove cyanide and ammonia; the use of a solar-powered circulation device to maintain an ice-free patch to prevent winterkill in Menzies Lake; the application of ammonium phosphate to the epilimnia of Kootenay and Arrow Lakes  to stimulate productivity and to halt a precipitous decline in endangered salmon populations; the siting of a prospective selective withdrawal intake in Coquitlam Reservoir to minimize turbidity; the hypolimnetic withdrawal of phosphorus laden water from a dredged hole in Chain Lake, together with replenishment with fresh water diverted from a nearby creek, to control eutrophication; the impact of internal wave damping in an unlogged reservoir on the reliability of a proposed low level cold water release from the Nechako Reservoir; the impact of reservoir operations on productivity in Kinbasket and Revelstoke Reservoirs; and the use of a water cap to “treat” hundreds of millions of cubic meters of tailings from the oil sands industry.

 

Dr. Lawrence has over 40 years of Civil Engineering experience as a public servant, researcher, consultant and professor.  His career has encompassed all aspects of Hydrotechnical Engineering, with particular emphasis on practical aspects of the dynamics of density stratified flows and physical limnology, including: the analysis of pollutant discharge problems; dynamics of lakes and water filled mine pits; flow instabilities, turbulence, chaos and mixing in density stratified flows; selective withdrawal from stratified reservoirs; internal hydraulics; lake fertilization and rehabilitation; and sediment resuspension in tailings ponds.  More recently, he has investigated the potential of in-stream tidal power and an analogy between open channel hydraulics and the physics of black-holes.

Dr. Lawrence’s expertise has been recognized at all levels.  He won the 1985 Straub award for the best Ph.D. thesis worldwide in Hydraulic Engineering or a closely related field.  He hosted the 5th International Symposium on Stratified Flows in 2000, and held the Canada Research Chair in Environmental Fluid Mechanics from 2001 until 2015.  Dr. Lawrence served on the Board of Governors of the University of British Columbia from 2001 – 2008.  Dr. Lawrence is a Fellow of the Canadian Academy of Engineering and the Canadian Society for Civil Engineering.  His awards include the Hans Albert Einstein Memorial Prize, the Lorenz G. Straub award and the Camille Dagenais award.