Roughness Effects on Wall-Bounded Turbulent Flows
Karen A. Flack
Department of Mechanical Engineering
United States Naval Academy, Annapolis, MD USA
The importance of surface roughness is well known for wall-bounded flows. Roughness typically increases drag in turbulent boundary layers due to pressure forces on the roughness elements. While rough-wall flows are ubiquitous in engineering practice, the issues of modeling the roughness in computations and accurately predicting the increase in frictional drag remain elusive goals. In this talk, the effect of roughness on the mean flow, turbulence statistics, and turbulence structure will be discussed. In particular, rough-wall flows will be examined in light of Townsend’s Reynolds number similarity hypothesis, which states that the turbulent motions in the outer layer are independent of surface roughness when the Reynolds number is sufficiently high. Many results over a range of roughness types lend support to Townsend’s hypothesis. However, it has been shown that two-dimensional roughness can have a significant impact on the outer layer turbulence, even when the roughness height is very small compared to the boundary layer thickness. Additionally, the presentation will include recent work on the estimation of frictional drag due to surface roughness. Detailed experiments have been performed in the transitionally rough and fully rough regimes. This research is part of an effort to determine the relevant predictive scales based solely on the roughness topography.
Karen A. Flack is a professor of Mechanical Engineering at the United States Naval Academy in Annapolis, Maryland. She received a bachelor’s degree from Rice University, a master’s degree from the University of California, Berkeley and a Ph.D. from Stanford University, all in Mechanical Engineering. Professor Flack teaches courses in thermodynamics, fluid mechanics, heat transfer, as well as wind and tidal power. Her research focuses on turbulent boundary layer physics with a concentration on rough wall boundary layers and frictional drag prediction. Recent work also includes performance characteristics of tidal turbines in unsteady flow conditions. She is chair of the American Physics Society, Division of Fluid Dynamics Outreach and Mentoring committee and on the editorial board of the International Journal of Heat and Fluid Flow. She is the recipient of the ASME award for best research paper in the Journal of Fluids Engineering, a Pi Tau Sigma teaching award and a United States government meritorious service medal.
Research and Development in Homecare Robotics
Clarence W. de Silva
Department of Mechanical Engineering
University of British Columbia, Vancouver, BC
This talk will address several important aspects of research and development in homecare robotics. Particular attention will be given to
two specific domains of application: autonomous robots that provide basic assistance to the elderly and the disabled in a home setting (e.g., serving food and medicine, cleaning, bathing,
and providing assistance for mobility); teleoperation of a robot from a hospital control room to provide first aid while the traditional emergency help is forthcoming. The vast majority
of the elderly and the disabled prefer to maintain independent households. The Canadian government annually spends about $ 9 billion on disability related matters. A significant fraction of
this cost goes into homecare and related expenses. The percentage of disabled adults among the population in Canada is estimated at 10%. The cost of basic care for a disabled person at
home is about $10,000/month, not factoring in special health needs. In this context, the benefits of homecare robotics are tremendous. In particular, the quality of life of the elderly and
the disabled will improve, allowing them more flexibility and comfort, in the presence of round-the-clock and reliable care. Also, other members of the household will have increased
freedom and peace of mind to pursue their normal activities including employment and education. Furthermore, the government spending will be more uniform, fair, and cost effective.
In the anticipated robotic homecare scenario, one or more robots will be available with their local sensors and a range of networked global sensors in the home environment. Adequate robotic intelligence is crucial for autonomous operation while haptic feedback is important in teleoperation. Sensory, mobility, grasping, manipulation, and control capabilities are needed for both categories of operation. The needed basic technologies of robotics, networked communication, control, and teleoperation are sufficiently mature and are available at reasonable cost. Further development is needed in assistive technologies, specialized end-effector devices, and haptics. The talk will particularly highlight key technologies of object identification and localization, detection and evaluation of abnormal motions in humans, robotic navigation in the presence of static and dynamic obstacles, grasping and manipulation, networked intelligent sensor fusion and feedback, impedance control in haptic teleoperation, and stabile operation, which are pertinent in the two application domains.
Clarence W. de Silva is a Professor of Mechanical Engineering and occupies the Tier 1 Canada Research Chair Professorship in Mechatronics & Industrial Automation at the University of British Columbia, Vancouver, Canada. A Professional Engineer (P.Eng.), he is also a Fellow of: ASME, IEEE, Canadian Academy of Engineering, and the Royal Society of Canada. He has received many awards includingthe Paynter Outstanding Investigator Award and the Takahashi Education Award of ASME Dynamic Systems and Control Division;Killam Research Prize;and Outstanding Engineering Educator Award of IEEE Canada. He has served as Editor/Associate Editor of 14 journals including ASME and IEEE transactions; and is the Editor-in-Chief of the International Journal of Control and Intelligent Systems. He received Ph.D. degrees from Massachusetts Institute of Technology, USA (1978) and the University of Cambridge, UK (1998), and an Honorary D.Eng. from the University of Waterloo (2008). He has authored 20 books and over 400 papers, half of which are in journals. The most recent books are: De Silva, C.W., Mechatronics—a Foundation Course, Taylor & Francis/CRC Press, Boca Raton, FL, 2010; De Silva, C.W., Modeling and Control of Engineering Systems, Taylor & Francis/CRC Press, Boca Raton, FL, 2009; De Silva, C.W., Vibration—Fundamentals and Practice, 2nd Edition, Taylor & Francis/CRC Press, Boca Raton, FL, 2007; and De Silva, C.W., SENSORS AND ACTUATORS—Control System Instrumentation, Taylor & Francis/CRC Press, Boca Raton, FL, 2007.
Soft active materials—when mechanics meets chemistry
Soft materials can mimic a salient feature of life: deformation in response to diverse stimuli. For example, an electric field can cause an elastomer to stretch several times its length. As another example, a change in pH can cause a gel to swell many times its volume. Long and flexible polymers can be covalently crosslinked to form a three-dimensional network, namely, an elastomer. The network can imbibe a solvent and swell, forming an elastomeric gel. Gels have many uses, including personal care, drug delivery, tissue engineering, microfluidic regulation, and oilfield management. Mixtures of macromolecular elastomers and mobile molecules also constitute most tissues of plants and animals. The amount of swelling can be large and reversible, regulated by environmental stimuli, such as force, electric field, pH, salinity, and light. This talk describes a theory that combines the mechanics of nonlinear fields and the chemistry of molecular mixtures. The theory is illustrated with examples of swelling-induced large deformation, contact, and bifurcation. The theory is further illustrated with recent experiments.
Zhigang Suo is Allen E. and Marilyn M. Puckett Professor of Mechanics and Materials at Harvard University. He earned a bachelor degree from Xi'an Jiaotong University in
1985, majoring in Engineering Mechanics. Upon earning a Ph.D. degree in Engineering Science from Harvard University, in 1989, Suo joined the faculty of the University of California at
Santa Barbara, and established a group studying the mechanics of materials and structures. The group moved to Princeton University in 1997 and to Harvard University in 2003.
Suo teaches courses in solid mechanics and applied mathematics. His research centers on the mechanical behavior of materials and structures. Basic processes include fracture, deformation, polarization, and diffusion, driven by various thermodynamic forces (e.g., stress, electric field, electron wind, chemical potential). Applications are concerned with microelectronics, large-area electronics, soft materials, and active materials.
With Teng Li, Suo co-founded iMechanica, the web of mechanics and mechanicians. He is a member of the Executive Committee (2005-2010) of the Applied Mechanics Division, of the American Society of Mechanical Engineers (ASME), and is a member at large of the US National Committee on Theoretical and Applied Mechanics (2006-1010).
Suo is a recipient of the Humboldt Research Award. He won the Pi Tau Sigma Gold Medal and the Special Achievement Award for Young Investigators in Applied Mechanics, both from ASME. He is a member of the US National Academy of Engineering.