Code UG Weekly Notes 5-16-02

Physical Sciences Division
Weekly Highlights for Week Ending 5/16/2002

*** Indicates item is appropriate for the HQ senior staff and may appear
on the OBPR Web site: http://spaceresearch.nasa.gov

EDUCATION and OUTREACH

NCMR EDUCATIONAL OUTREACH – SPACE DAY AT THE AKRON AT THE INVENTOR’S HALL OF FAME: May marks a busy month for the K-12 Educational Outreach program in public and school outreach. NCMR’s Carol Hodanbosi and sabbatical teacher Ann Schwartz accompanied Microgravity division scientist Dennis Stoker and Outreach Manager Ihor Kyrik to the Space Day Event in Akron at the Inventor’s Hall of Fame at the beginning of the month. At this event open, visitors watched demonstrations using the mini drop tower and had over 600 pictures taken in an Space Day astronaut scene.

AMUSEMENT PARK PHYSICS TIME: NCMR and the Microgravity Division personnel will be on hand to link microgravity to Amusement Park Physics at Cedar Point and Six Flags. Amusement Park Physics Days will be held at Cedar Point on May 10 and at Six Flags on May 17 and 22. This year 10 middle school educators from all over Ohio are participating in the NCMR Amusement Park Physics pilot program. They will take a field trip to Cedar Point, Six Flags, Kennywood, and Kings Island to use the pilot program ride worksheets at theses parks to measure ride velocities and accelerations. The outreach team will make classroom visits to witness how the pilot pre-trip materials are working with the students before the field trip.

NATIONAL WINNERS OF THE PRESIDENTIAL AWARD FOR EXCELLENCE IN MATH AND SCIENCE: On May 29th, NCMR Curriculum Developer Carol Hodanbosi will serve as a committee member to review the applications and send recommendations to the National Science Foundation to select National Winners of the Presidential Award for Excellence in Math and Science. This effort is sponsored by the Ohio Department of Education.

EXPEDITION 4 ACTIVITY FOOTAGE FROM THE INTERNATIONAL SPACE STATION: Raw footage of NCMR educational activities from Expedition 4 is due to arrive back at Glenn Research Center by the end of May. Astronauts performed and videotaped three microgravity activities in February of 2002 and have just returned with the raw footage. This footage will be edited and dubbed with voice overs to be used in educational workshops and as a web resource for teachers.

ISS FLIGHT PROGRAM

MICROGRAVITY RESEARCH PROGRAM OFFICE (MRPO) PAYLOAD OPERATIONS STATUS ON THE INTERNATIONAL SPACE STATION (ISS) 8A STAGE: Physical Sciences payloads have successfully completed Week#21 of Increment 4/8A Stage, and have entered into Week#22. All payloads are performing nominally at this moment. Troubleshooting for SAMS, the acceleration measurement system, was finally successful in binging it back to functioning state. Preparations are now in progress to ready new payloads for ascent on Flight UF2, scheduled for launch on 5/30/02.

GLOVEBOX INTEGRATED MICROGRAVITY ISOLATION TECHNOLOGY (g-LIMIT): The flight unit for the g-LIMIT experiment passed a major milestone with the successful completion of the system bench functional tests. In addition, the project was notified that the current system Electromagnetic Interference (EMI) exceedances measured during development tests can be waived by the International Space Station (ISS) EMI/Electromagnetic Compatibility (EMC) Panel. These two proceedings clear the way for the completion of the g-LIMIT verification activity, beginning with EMI verification tests this week. The g-LIMIT project is planning to the ISS-11A flight (10/6/02, STS-105, Endeavor), as a first priority candidate, currently below the line for manifesting.

RADIATIVE ENHANCEMENT EFFECTS ON FLAME SPREAD (REEFS): Prof. P. Ronney from University of Southern California investigates flame spread over flat solid fuel beds as a useful means of understanding more complex, two-phase, non-premixed flames, such as those found in fires in enclosures, e.g., manned spacecraft and terrestrial buildings. The goal of this work is to extend previous studies by employing µg experiments with emphasis on the atmospheres and flow environments likely to be present in fires which might occur at µg. During the 2.2-second drop tower and KC-135 tests at GRC, the PI introduced the use of foam fuels for flame spread experiments over thermally-thick fuels to obtain large spread rates compared to dense fuels such as PMMA. This enables meaningful results to be obtained even in 2.2-second drop tower experiments. Thick-fuel flame spread experiments using foam fuels revealed that in contrast to conventional understanding; steady spread can occur over thick fuels in quiescent microgravity environments, especially when a radiatively active diluent gas such as CO2 is employed, as the PI had hypothesized. As with thin fuels, the spread rates at microgravity can exceed those at earth gravity when a radiatively active diluent gas is used. This was shown to be due to radiative transfer from the flame to the fuel surface that can lead to steady spread even when conductive heat transfer from the flame to the fuel bed is negligible. These results are particularly noteworthy considering that the International Space Station employs CO2 fire extinguishers; these results suggest that helium may be a better extinguishing agent on both mass and mole bases at microgravity even though CO2 is much better on a mole basis at earth gravity.

SCIENCE HIGHLIGHTS

COMBUSTION SCIENCE:

SPECIES CONCENTRATION MEASUREMENTS USING DIODE LASER SPECTROSCOPY IN A REACTING VORTEX RING USING THE NOVEL ITAC METHOD: This is a Graduate Student Researchers Program award, with the student J. Mullin under the direction of Prof. Werner Dahm of the University of Michigan, and is a collaborative effort with Southwest Sciences. This effort will combine experimental diode laser measurements with the recently developed Iterative Temperature with Assumed Chemistry (ITAC) method by Southwest Sciences. This approach will extend the utility of the diagnostic method by allowing multiple species to be determined using a simpler hardware from measurement of a single species when equilibrium chemistry can be assumed, and from two species (one major and one minor) when non-equilibrium models are more appropriate. The diagnostic method will be applied to the study of vortex ring diffusion flames. These flames incorporate many of the phenomena of turbulent combustion including vorticity, entrainment and mixing, strain and non-equilibrium phenomena, diffusion and differential-diffusion, and partial premixing and diluent effects, in a configuration that is more reproducible than most turbulent systems. In this reporting period, the graduate student calculated state relationships for major species and temperature using CEA code with several chemical kinetics mechanisms, specifically GRI-Mech versions 1.2, 2.11, and 3.0, and SD-Mech. He also calculated major and some minor species using the OPPDIF code with the same four kinetics mechanisms, at two different strain rates. As expected, in all calculations, the differences among the different versions of GRI-Mech were minor, as the reaction list is mostly the same with a few additional reactions. In changing from CEA to OPPDIF, many of the gross features remain qualitatively similar; however, the temperature relation shows an inflection point in the CEA calculation which is smoothed out in the OPPDIF calculation. O2 and CH4 calculations were qualitatively similar though quantitatively different in the two approaches. H2O and CO2 calculations differed substantially and their behavior was noticeably different even in the qualitative shape of the curves. With the OPPDIF codes, calculations of OH, CO, and NO differ substantially from those done with CEA, and within OPPDIF, the SD-Mech gave different results for these species than the three GRI-Mech calculations. These sets of calculations will provide direction for future measurements as several species are sensitive to the different modes of calculation and direct measurement will help determine the best codes for this system.

FLUID PHYSICS:

THE EFFECTS OF THERMAL MODULATION UPON THE ONSET OF MARANGONI BENARD CONVECTION:
Fluid Physics PI Prof. R. Kelly (University of California, Los Angeles) and his ream have investigated the effects of thermal modulation with time on the thermocapillary instability of a thin horizontal fluid layer with a deformable free surface on the basis of linear stability theory. First, a sinusoidal heating with a mean component is applied at the lower wall, corresponding to boundary conditions either in the form of prescribed temperature or heat flux. For finite-wavelength convection the thermal modulation exerts a strong effect, giving rise to a family of looped regions of instability corresponding to alternating synchronous or subharmonic responses. In the case of prescribed heat flux, the critical curve consists of significantly fewer loops than in the case of prescribed temperature. Thermal modulation with moderate modulation amplitude tends to stabilize the mean basic state, and optimal values of frequency and amplitude of modulation are determined to yield maximum stabilization. However, large-amplitude modulation can be destabilizing. A basic state with zero mean is then considered and the critical Marangoni number is obtained as a function of frequency. The effects of modulation are also investigated in the long-wavelength limit. For the case of prescribed temperature, the modulation does not affect the onset of the long-wavelength mode associated with the mean basic state and a purely oscillating basic state is always stable with respect to long-wavelength disturbances. For the case of prescribed heat flux both at the wall and free surface, by contrast, thermal modulation exerts a significant effect on the onset of convection from a mean basic state and long-wavelength convection can occur even for a purely oscillating basic state. The modulation can be stabilizing or destabilizing, depending on the frequency. [A. C. Or and R. E. Kelly, "The effects of thermal modulation upon the onset of Marangoni Benard convection," J. Fluid Mech. (2002), vol. 456, pp. 161-182, 2002.]

THE EFFECTS OF THERMAL MODULATION UPON THE ONSET OF MARANGONI BENARD CONVECTION: Fluid Physics PI Prof. R. Kelly (University of California, Los Angeles) and his ream have investigated the effects of thermal modulation with time on the thermocapillary instability of a thin horizontal fluid layer with a deformable free surface on the basis of linear stability theory. First, a sinusoidal heating with a mean component is applied at the lower wall, corresponding to boundary conditions either in the form of prescribed temperature or heat flux. For finite-wavelength convection the thermal modulation exerts a strong effect, giving rise to a family of looped regions of instability corresponding to alternating synchronous or subharmonic responses. In the case of prescribed heat flux, the critical curve consists of significantly fewer loops than in the case of prescribed temperature. Thermal modulation with moderate modulation amplitude tends to stabilize the mean basic state, and optimal values of frequency and amplitude of modulation are determined to yield maximum stabilization. However, large-amplitude modulation can be destabilizing. A basic state with zero mean is then considered and the critical Marangoni number is obtained as a function of frequency. The effects of modulation are also investigated in the long-wavelength limit. For the case of prescribed temperature, the modulation does not affect the onset of the long-wavelength mode associated with the mean basic state and a purely oscillating basic state is always stable with respect to long-wavelength disturbances. For the case of prescribed heat flux both at the wall and free surface, by contrast, thermal modulation exerts a significant effect on the onset of convection from a mean basic state and long-wavelength convection can occur even for a purely oscillating basic state. The modulation can be stabilizing or destabilizing, depending on the frequency. [A. C. Or and R. E. Kelly, "The effects of thermal modulation upon the onset of Marangoni Benard convection," J. Fluid Mech. (2002), vol. 456, pp. 161-182, 2002.]

EXPERIMENTAL INVESTIGATION OF CONVECTIVE MELTING OF GRANULAR PACKED BED UNDER MICROGRAVITY: Fluid Physics HBCU PI Prof. Tao (Tennessee State University) conducted experimental investigations to improve the understanding of convective melting of packed solid particles in a fluid to study the melting characteristics of a packed bed by unmasking the buoyancy forces due to the density difference between the melt and solid particles. A close-loop apparatus, named the particle-melting-in-flow (PMF) module, is designed to allow a steady-state liquid flow at a specified temperature. The module is installed onboard NASA’s KC-135 reduced gravity aircraft using ice particles of desired sizes and water as the test media. Experimentally determined melting rates are presented as a function of upstream flow velocity, temperature and initial average particle size of the packed bed. It is found that the melting rate is influenced mainly by the ratio of the Reynolds number (Re, based on the initial particle diameter) to the square of the Froude number (Fr), and the Stefan number (Ste). In general, the dimensionless melting rate decreases as Re/Fr 2 increases and increases as Ste increases. With the absence of gravity, i.e., as the Froude number approaches infinity, a maximum melting rate can be achieved. The increase in the melting rate proportional to the Stefan number also becomes more pronounced under the zero gravity condition. The trend of average and local Nusselt number of the melting packed bed under microgravity, as a function of Reynolds number and Prandtl number, is discussed and compared with the case of nonmelting packed bed. [J. Jiang, Y. Hao, and Y.-X. Tao, "Experimental Investigation of Convective Melting of Granular Packed Bed Under Microgravity," Journal of Heat Transfer, Vol. 124, pp 516-24, June 2002.]

AVALANCHE DYNAMICS IN WET GRANULAR MATERIALS: Fluid Physics PI Prof. Peter Schiffer (Pennsylvania State University) and his team have studied the dynamics of avalanching wet granular media in a rotating drum apparatus. Quantitative measurements of the flow velocity and the granular flux during avalanches allow them to characterize novel avalanche types unique to wet media. They also explore the details of viscoplastic flow (observed at the highest liquid contents) in which there are lasting contacts during flow, leading to coherence across the entire sample. This coherence leads to a velocity independent flow depth at high rotation rates and novel robust pattern formation in the granular surface. Avalanches and landslides are among the most dramatic of natural catastrophes, and they also provide an evocative metaphor for wide range of propagating breakdown phenomena from impact ionization in semiconductors to magnetic vortex motion in superconductors .On the other hand, the existence of avalanches, i.e. the sudden collapse of the system previously frozen into high energy state, is fundamental manifestation of the metastable nature of granular materials.

UPCOMING EVENTS

Additional meetings and symposia can be found at: http://microgravity.grc.nasa.gov/ugml/ugmltext.htm

The MRPO Program Calendar can be found at:
http://webcal.msfc.nasa.gov/webevent.cgi?cmd=opencal&cal=cal85&