Physical Sciences Division
Weekly Highlights for Week Ending 10/10/2001
*** Indicates item is appropriate for the HQ senior staff and may appear on the OBPR Web site: http://spaceresearch.nasa.gov
*** WOLFGANG KETTERLE WINS 2001 NOBEL PRIZE FOR PHYSICS: Fundamental Physics principal investigator Wolfgang Ketterle of MIT has been named one of three recipients of the 2001 Nobel prize in physics. Along with Eric Cornell and Carl Wieman of JILA and NIST, Ketterle was cited " for the achievement of Bose-Einstein condensation in dilute gases of alkali atoms, and for early fundamental studies of the properties of the condensates." NASA and JPL join with the physics community in congratulating Wolfgang on this well-deserved award. http://www.nobelprizes.com/
COMBUSTION INVESTIGATOR INDUCTED INTO US NATIONAL ACADEMY OF ENGINEERING: Combustion co-I Prof. Felix Weinberg was inducted into the US National Academy of Engineering last week. He is co-I on a ground-based combustion grant entitled, "Applications of Electric Field in Microgravity Combustion"; the PI is Prof. Derek Dunn-Rankin of University of California at Irvine. Prof. Weinberg of Imperial College has authored a book on "Optics and Flames" and done novel research both in this diagnostics area and in the use of electric and magnetic field effects in flames.
EDUCATION and OUTREACH
FEATURE ARTICLE ON THE MICROGRAVITY FLUID PHYSICS PROGRAM PUBLISHED IN AEROSPACE AMERICA: "Going with the flow: Microgravity fluid physics" is the title of an article published in the October 2001 issue of the AIAA magazine, Aerospace America, Vol. 39, No. 10, pg. 20-22.. The authors are Bhim Singh and Fred Kohl from NASA Glenn and Iwan Alexander from Case Western Reserve University and the National Center for Microgravity Research on Fluids and Combustion. This article is the fourth in a series that has already featured Combustion Science, Fundamental Physics and Materials Science. The article included descriptions of past highlights from the Fluid Physics discipline program and the promise of future results from the ISS.
ISS FLIGHT PROGRAM
PHYSICS OF COLLOIDS IN SPACE (PCS) ON ISS: During EXPPCS' 84 hours of operations over the last week, the focus of the research shifted away from the AB6 and AB13 samples to detailed characterizations of the Colloid-Polymer Gel and Colloidal Glass samples. Each sample was mixed and a variety of measurements were performed to watch the beginning of the structuring processes in these samples. These samples behave quite differently and scatter light quite differently from the binary colloidal crystals that have been extensively studied recently. As a result, both operators and experiment specifiers made small mistakes in configuring some of the experiments. Operations are now on track, but the glass sample will be remixed during the next week to recover some lost data.
REQUIREMENTS DEFINITION REVIEW HELD AT GRC: Requirements Definition Review (RDR) for the Fluid Physics flight definition experiment "Microscale Hydrodynamics near Moving Contact Lines" was held at GRC on 10/2/01. The moving contact line is a key problem in the understanding and predictive modeling of a host of technologically important processes. Some of these occur in a terrestrial environment; such as oil recovery, the manufacturing of advanced composite materials, and chemical and biological processing in microfluidic devices employing new "Lab-on-a-Chip" technologies. Dr. Gerald Pitalo, Fluid Physics Enterprise Scientist at NASA HQ Code U convened the review. Prof. Stephen Garoff (Carnegie Mellon) is the PI and Dr. Enrique Rame (NCMRFC/GRC) is teh Co-I. This experiment is designed for ISS. Dr. David Jacqmin (GRC) is the Project Scientist and Amy Jankovsky (GRC) is the Project Manager.
UNSTEADY MULTIDIMENSIONAL NUMERICAL SIMULATIONS OF FLAME-VORTEX INTERACTIONS IN MICROGRAVITY: This research, being led by Dr. G. Patnaik at the Naval Research Labs, studies flame-vortex interactions (FVI), which play an important role in the propagation and extinguishment of turbulent flames. Most studies of FVI ignore the effects of gravity, however, recent microgravity experiments show that a reduction in gravity can significantly alter the structure of the flame produced by the FVI. There are a number of plausible and often conflicting explanations for these differences. A richer understanding of FVI is possible if the numerical simulations closely complement laboratory experiments. In this study, detailed time-dependent, multi-dimensional numerical simulations are used to investigate the relative importance of the processes occurring in the flame-vortex interactions in normal and reduced gravity. Towards that end, a flame from a small kernel at one end of a tube filled with the premixed lean methane-air mixture is initiated. The flame begins to propagate toward the closed end. At a certain time, a vortex of sufficient strength is created within the tube and moves towards the oncoming flame. The ensuing interaction causes a pocket of flame to be pinched off. This calculation has been carried out for -1g, zero g and +1g (-1g corresponds to downward propagation, +1g to upward). It is clear that gravity affects the flame shape even prior to the interaction with the vortex. The interaction itself in the three cases has both differences and similarities. Several interesting questions arise: Are the differences due to the variations in flame shape, or are they due to gravity, though gravity itself has determined the flame shape? The influence of flame shape and gravity needs to be sorted out in order to understand what the basic role of buoyancy is.
DETERMINATION OF COOL FLAME QUENCHING DISTANCES AT MICROGRAVITY: This research is being conducted by Dr. H. Pearlman from the University of Southern California. Quenching due to conduction heat loss has received much attention as it pertains to hot flames, yet little attention has been given to cool flame quenching. It is generally presumed that cool flame quenching distances are larger than those associated with hot flames, however this presumption has never been put to a rigorous test. This study has two objectives, (1) to isolate the role of conduction heat loss on cool flame quenching, and (2) to determine if cool flames can propagate through hot flame quenching distances (and vice versa) for conditions that support both flame types. To wards this end, a new vessel for studying cool flame quenching distances has been fabricated. It consists of a gradually tapered quartz tube. The near future plan is to first use this vessel in the lab for measuring quenching distances associated with cool flames of butane and propane (diluted) with oxygen, and subsequently, compare the results to experiments on the KC-135 airplane.
THEORY PROPOSED TO EXPLAIN VOIDS IN DUSTY PLASMAS: Fluid Physics PI Prof. J. Goree (U. of Iowa) and colleagues have proposed a theory describing the formation of voids in dusty plasmas, which are laboratory plasmas containing micron-scale particles. A dust void, i.e., the dust-free region in a dusty plasma, results from the balance of the electrostatic and plasma (such as the ion drag) forces acting on a dust particle. The properties of dust voids depend on the ratio of the void size to the mean free path of plasma ions colliding with neutral species of a weakly ionized plasma. For many plasma-processing and plasma-crystal experiments, the size of the void is much larger than the ion-neutral mean free path. The researchers present theory and numerical results for such a collisional case including the situations in which the plasma is quasineutral in the void region or the plasma quasineutrality is violated, as well as the case in which the ion ram pressure is insignificant. Dusty plasma research is a rapidly growing field with applications ranging from fundamental studies of freezing and melting phase transitions to the formation of stars to the control of contamination in the processing of semiconductor devices. This work is reported in the following paper:
V.N. Tsytovich, S.V. Vladimirov, G.E. Morfill, and J. Goree,"Theory of collision-dominated dust voids in plasmas," Physical Review E Vol. 63, pp. 056609-1 056609-11 2001.
SUMO PAPER PRESENTED AT RELATIVITY CONFERENCE: John Lipa of Stanford University reports that Dr. J. Nissen presented an invited talk on the SUMO flight experiment program at the 2nd CPT and Lorentz Invariance Conference in Bloomington, Indiana in August. The conference focused on potential departures from the Standard Model of matter, some of which can be tested with precision clocks like SUMO. It is expected that SUMO will be able to make a number of unique contributions in this area, in addition to the more direct tests of relativity theory initially planned for the experiment. Calculations on SUMO's sensitivities are in progress at Indiana University.
RICE GROUP PUBLISHES PAPER IN PHYSICAL REVIEW: The authors describe their observations of a light-induced frequency shift in the single-photonphotoassociative spectra of magnetically trapped, quantum degenerate Li-7. The shift is a manifestation of the coupling between the threshold continuum scattering states and discrete bound levels in the excited-state molecular potential induced by the photoassociation laser. The frequency shift is observed to be linear in the laser intensity with a measured proportionality constant that is in good agreement with theoretical predictions. The frequency shift has important implications for a scheme to alter the interactions between atoms in a Bose-Einstein condensate using photoassociation resonances.
Randy Hulet of Rice University reports that the following paper has been accepted for publication in Physical Review A: "Photoassociative Frequency Shift in a Quantum Degenerate Gas", by J. M. Gerton, B. J. Frew, and R. G. Hulet
Additional meetings and symposia can be found at: http://microgravity.grc.nasa.gov/ugml/ugmltext.htm
September 19-20, 2001 Face-To-Face MRT Meeting, JSC
October 14-18, 2001, 17th Interdisciplinary Laser Science Conference, Long Beach Convention Center, Long Beach, CA
October 18, 2001, TeleConference MRT Meeting, 10:00am - 02:00pm CST
November 15, 2001, TeleConference MRT Meeting, 10:00am - 02:00pm CST
December 12-13, 2001, Face-To-Face MRT Meeting, MSFC