Scientific and Technical Aerospace Reports Volume 39 April 6, 2001

the first time, non-intrusive, high-accuracy dynamic measurement of velocity gradient and vorticity. The direct, non-contact measurement
of the velocity gradients and vorticity will lead to analysis of turbulent flow physics and combustion phenomena.
Author (revised)
Microgravity; Fluid Dynamics; Fluid Mechanics; Laser Beams; Laser Doppler Velocimeters; Nonintrusive Measurement; Velocity
Distribution; Velocity Measurement
20010024970 Tufts Univ., Dept. of Mechanical Engineering, Medford, MA USA
Decoupling the Roles of Inertia and Gravity on Particle Dispersion
Groszmann, D., Tufts Univ., USA; Rogers, C., Tufts Univ., USA; Proceedings of the Fifth Microgravity Fluid Physics and Transport
Phenomena Conference; December 2000, pp. 1298-1306; In English; See also 20010024890; No Copyright; Avail: CASI;
A02, Hardcopy; A10, Microfiche
The motion of solid particles in a turbulent flow field is dictated by their response to inertial and gravitational forces. Gravity
plays the dominant role in this motion by pulling the particles through adjacent regions of fluid turbulence, masking the inertial
effects. by examining the dispersion of solid particles in a turbulent flow in the absence of gravity, we can improve our understanding
of the mechanisms responsible for particle motion and develop new models for these effects. In this paper we present the particle
dispersion experiments conducted on NASA’s KC-135 Reduced-Gravity Aircraft, which generates microgravity conditions
for 20 seconds. The turbulent flow field was generated in a closed Lexan box measuring 30.5 cm x 30.5 cm x 30.5 cm by 8 small
fans mounted in the corners. Laser Doppler velocimetry measurements inside the box were used to characterize the flow parameters
before conducting the microgravity experiments. The measurements show the turbulence to be nearly isotropic, having an
isotropy ratio of 0.97, with up to two orders of magnitude in turbulent scales and with a near-zero mean flow in the center region.
to cover a broad range of flow regimes of interest, particles with Stokes numbers of about 0.1, 1, and 10 were released in the turbulence
box and the particle motion in two and three dimensions were measured. The two-dimensional measurements were made
by recording and measuring particle concentrations in a 4 cm thick light sheet that highlighted a plane in the flow. Results show
preferential concentration of particles with a Stokes number of about unity in microgravity conditions but with no preferential
concentration in Earth’s gravity, suggesting that particle dispersion has a strong dependence on gravitational forces. Figure 1a
shows a sample video image highlighting the preferential concentration of 300-350 micron glass particles. Figure 1b compares
the average minimum distance between particles (DP) with DNS results. Three-dimensional measurements of particle motion
were made using a three-camera (monochrome 60 Hz) stereo imaging system with a particle-tracking algorithm. Standard
photogrammetric techniques were used to determine the particle location in three-dimensional space from the calibrated camera
images. to simplify the camera recording process, the monochrome images from each of the three cameras were encoded in red,
green, and blue, combined into one color image, and recorded digitally on a DV recorder. An included figure shows a portion of
a sample image with all three-camera views of 600-700 micron glass particles superimposed. A single particle is highlighted in
each of the three camera views (or color planes). The epipolar geometry constraint was used to identify matching particles from
the three different views and these are shown for one particle in the image. Once a particle’s position is determined in each of the
three camera views, its coordinates in three-dimensional space are determined from the camera calibration parameters. Using
velocity and acceleration constraints, particles in a sequence of frames can be matched resulting in particle tracks. A sample track
in three-dimensional space for a 600-700 micron glass particle is shown. Quantitative three-dimensional particle dispersion results
together with our previous work in preferential concentration will provide additional insight into the mechanisms of particle-laden
turbulent flows. We can compare the dispersion rates of different Stokes number particles in zero g. In addition, we are continuing
work with the turbulence box, using a microcontroller to adjust the speeds of individual fans in an attempt to improve the isotropy
of the turbulence.
Author (revised)
Gravitation; Gravitational Effects; Inertia; Microgravity; Turbulence Effects; Particles; Turbulent Flow
20010024971 University of Southern California, Dept. of Aerospace and Mechanical Engineering, Los Angeles, CA USA
Ground Based Studies of Thermocapillary Flows in Levitated Laser-Heated Drops
Sadhal, S. S., University of Southern California, USA; Rednikov, A., University of Southern California, USA; Ohsaka, K., University
of Southern California, USA; Proceedings of the Fifth Microgravity Fluid Physics and Transport Phenomena Conference;
December 2000, pp. 1307-1321; In English; See also 20010024890; No Copyright; Avail: CASI; A03, Hardcopy; A10, Microfiche
The IFFD (Internal Flows in Free Drops) investigation were carried out on STS-95 produced good video images with optimal
resolution of the internal tracer particles will allow the accurate measurement of the internal motion of the liquid. The first demonstration
of non-contact fissioning of a single drop into two parts was obtained with a static sound field. In addition, the new technique
for the accurate, acoustically-assisted drop deployment in microgravity has also been verified together with the feasibility
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