Friday, November 6 • 2:30 PM – PWEB, Rm. 175

Analysis of Convection in the Presence of Apparent Slip

Marc Hodes

Associate Professor of Mechanical Engineering Tufts University, Medford, Massachusetts

Abstract: A liquid flowing over a structured surface in the form of, e.g., ridges parallel to the flow, may be suspended in the unwetted (Cassie) state. I will introduce the physical principles and micro/nanotechnology that are exploited to trap a liquid in this state, where the no-slip boundary condition does not apply. This complicates the solution of the Stokes (or Navier-Stokes) equations for the velocity profile as it imposes different types of boundary conditions along the solid-liquid interface and the liquid-gas interface (meniscus). The vast majority of previous research on such flows considered them adiabatic. We study them in the presence of heat transfer, where the thermal energy equation is too subjected to non-standard boundary conditions. We have solved a variety of diffusive “inner” problems in the vicinity of the structures, where a boundary condition that the flow or temperature field is 1-dimensional infinitely far away from the structures may be imposed. These yield expressions for the apparent hydrodynamic and thermal slip lengths that manifest themselves as Robin boundary conditions on the outer problems that span the whole domain, e.g., a parallel plate channel. Additionally, in the outer thermal problems, advection must be considered. I will present our conformal map and convolution theory-based analytical solution to an inner thermal problem that captures the effects of evaporation and condensation along menisci. Then, I will discuss our analytical results for the Nusselt number (Nu) governing an outer thermal problem where arbitrary and asymmetric hydrodynamic and thermal (apparent) slip are imposed on a thermally-developing Couette flow. Nu is in the form of Airy and exponential function-containing infinite series, where the first term corresponds to the thermally-developed flow limit. Lastly, I will discuss our present work on the effects of thermocapillary stress and meniscus curvature on both types of apparent slip lengths.

Biographical Sketch: Marc Hodes received his M.S. in Mechanical Engineering from the University of Minnesota, where he performed research on dielectric liquid cooling of microelectronics. In 1998, he received his Ph.D. in Mechanical Engineering from the Massachusetts Institute of Technology, where his research addressed salt deposition (fouling) in supercritical water oxidation reactors used for the destruction of hazardous organic wastes. After holding a succession of appointments from Postdoctoral Member of Technical Staff to Manager over a 10 year period at Bell Labs, he joined the Mechanical Engineering Department at Tufts University in the Fall of 2008 as an Associate Professor. Professor Hodes’ research interests are in heat and mass transfer and, over the course of his career, four thematic areas have been addressed, i.e., 1) the thermal management of electronics, 2) mass transfer in supercritical fluids, 3) analysis of thermoelectric modules and 4) analysis of convection in the presence of apparent slip. Current research is in two areas. First, analytical solutions for apparent hydrodynamic and thermal slip lengths for liquid flows over diabatic structured surfaces that capture the effects of curvature, thermocapillary stress or evaporation and condensation at menisci are being developed. Secondly, enhanced aircooled heat sinks are being developed by deriving semi-analytical optimization formula for longitudinal-fin geometry heat sinks that capture the effects of non-uniform heat transfer coefficients and by developing manufacturing methods for novel “three-dimensional” geometries. Students conducting research with Professor Hodes enroll in part of all of his 4 course sequence of undergraduate fluid mechanics, undergraduate heat transfer, thermal management of electronics and graduate heat transfer. Since joining Tufts University in the fall of 2008 Professor Hodes’ research has been supported by the Department of Energy, NSF, DARPA, Science Foundation Ireland, the Wittich Energy Sustainability Research Initiation Fund, Tufts University and domestic and foreign industrial partners.

For additional information, please contact Prof. Michael T. Pettes at (860) 486-2855, pettes@engr.uconn.edu or Laurie Hockla at (860) 486-2189, hockla@engr.uconn.edu

Friday, October 30 • 2:30 PM – PWEB, Rm. 175

The Science and Engineering of Developing Reliable Electronic Systems

Prof. Abhijit Dasgupta Jeong H. Kim

Professor of Mechanical Engineering Center for Advanced Life Cycle Engineering (CALCE)

University of Maryland, College Park, MD 20742

Abstract: This presentation will focus on some of the interesting lessons learned at the CALCE Center over the past 30 years in the science and technology of material aging mechanisms and system degradation modes in complex electronic systems. Modern engineering systems are becoming extremely electronics-rich where the electronics are intrinsically multi-functional systems with highly multi-physics aging and degradation mechanisms under complex life-cycle environmental and operational stress combinations. At the same time, ever-increasing demands for miniaturization have extended the degradation physics into the nano-to-micro length scales, requiring rigorous multi-scale approaches. A few interesting examples of such multi-physics multi-scale degradation mechanisms include creep-fatigue in high-temperature interconnect metal alloys, ‘cold-welding’ in gold-gold interconnects by solid-state diffusion, leakage currents due to the electro-chemistry of dendritic growth in metallization, and dielectric breakdown due to quantum tunneling effects. This pressure for miniaturization, combined with the need for increased functionality and increased affordability, have placed tremendous pressure on the science and technology of achieving and assuring reliability in complex electronic systems. Conducting this type of application-driven fundamental and applied research in a university setting, within the context of graduate thesis and dissertation research, poses unique challenges and imparts special training and skills to the student researchers, to equip them for a very diverse employment landscape. An overview and a few selected examples will be provided during this presentation, with particular emphasis on important lessons that graduate students can take away on how to prepare for the modern-day multi-disciplinary work-place and research environment.

Biographical Sketch: Dr. Abhijit Dasgupta, Jeong H. Kim Professor of Mechanical Engineering, has been teaching at University of Maryland since he obtained his Ph.D. in Theoretical & Applied Mechanics from the University of Illinois in Urbana-Champaign in 1988. His expertise is in the multi-physics, multi-scale constitutive behavior and damage mechanics of engineered materials, for applications in reliability assessment, for real-time health monitoring, and for accelerated stress testing of electronic/photonic systems, ‘smart’ structures, MEMS, and nanoscale structures. This research is funded by an international consortium of leading electronics manufacturers as well as by government funding agencies as NSF, ARL and ARO. He is an ASME Fellow and the current Chair of the Electronic and Photonics Packaging Division of ASME.
For additional information, please contact Prof. Xinyu Zhao at (860) 486-0241, xinyuz@engr.uconn.edu or Laurie Hockla at (860) 486-2189, hockla@engr.uconn.edu

Friday, October 23 • 2:30 PM – PWEB, Rm. 175

A Quest for the Ideal Solution in engineering design. Five challenges of BTIPS.

Dr. Zbigniew M. Bzymek, University of Connecticut, Mechanical Engineering

Abstract: The nature of engineering is problem solving. The process starts with the problem definition and is followed by the search of a solution that satisfies the most requirements. Such a solution is an End Solution of the process and it changes into an Ideal Solution which determines the success of the design. So the starting point of the design process is the conceptual solution. Finding the right conceptual solution determines the success of the product. If the concept is not right, even the most sophisticated geometry and the most precise analyses will not lead to a successful product. Evident concepts are not hard to find. The real challenge occurs when engineers have to solve the problem with conflicting constraints that are described by antonyms as for example: “is there and is not there”, “close and far”, “hard and soft” and so on. BTIPS – a Brief Theory of Inventive Problem Solving is a method of conceptual design that is helpful in solving such conflicting constraints. BTIPS originated from Altshuller’s TRIZ1 and Invention Machine TIPS2 . It was developed from these two methods at the University Connecticut by introducing abbreviations, changes and additions based on the newest theoretical and practical achievements of Science and Technology. BTIPS was developed mainly for teaching but it is powerful enough to be applied in engineering practice. BTIPS, similar to IM TIPS, contains three modules: Principles, Effects and Prediction. During the research at UConn three were new principles were added to the PRINCIPLES module, several effects to the EFFECTS module and virtual elements to the PREDICTION module. In the solution process algorithm improvements of the sequence of modules was introduced. To confirm the Ideal Solution two tests of the End Solution were established. Five challenges were also added. as the introduction to BTIPS. The five challenges are: “Solve Impossible”,” Isolate Properly”, “Choose the Right Solution Tool”:”Separate Functions” and “Point the Ideal Solution”. Overcoming all five challenges would allow the designer to accomplish the Quest for the Ideal Solution. TRIZ1 – /ˈtriːz/; Russian: теория решения изобретательских задач, teoriya resheniya izobretatelskikh zadach, literally: “theory of solving of inventive problems”); TIPS2 – Theory of Inventive Problem Solving.

Biographical Sketch: Zbigniew M. Bzymek, Ph.D., Associate Professor of Mechanical Engineering at UConn is a contributor to Design Theory, Designer and Constructor of Structures, Researcher and Educator of Engineers. He has received PhD in 1968, M.Sc. from Warsaw University of Technology in 1959 and M.Sc. from University of Michigan, Ann Arbor, Michigan in 1961. As a result of extensive research in Poland he put together several packages of computer programs for stress and deflection analysis of structures. He has published the first book in Polish on computer analysis of structures (translated to Hungarian), which also was one of the first in Eastern Europe. He has delivered over 50 invited lectures and seminars on the design and CAD of structures at universities, at computational centers as well as in design and consulting offices in Poland, Hungary, Czechoslovakia, Soviet Union, Germany, UK, US, China, Australia, Dubai, Mexico and Canada. He modernized the CAD and Manufacturing Automation courses taught at UConn and developed a CAD &CAM Laboratory – one of the most unique and significant on the East coast. For contribution to computer multicolor, multi-thickness line drawing he was awarded the title of Computer Graphics Pioneer in the United States. He has contributed to the conceptual design by introducing several principles. Together with his students he has received several recognitions and industrial design awards as well as the Second National ASME Design Award. He has published over 150 articles, conference papers, books and chapters. His conference papers were presented in the US, Canada, Japan, Australia, Mexico, New Britain, Poland and other European countries. He is an Associate Member of Engineering Committee of the Polish Academy of Science and Member of the New York Academy of Science. He has been awarded an ASME medal and is an ASME Fellow.

For additional information, please contact Prof. Xinyu Zhao at (860) 486-0241, xinyuz@engr.uconn.edu or Laurie Hockla at (860) 486-2189, hockla@engr.uconn.edu