HR: 1340h
AN: H53E-1471    [Abstracts]
TI: Numerical Modeling of Unsaturated Flows in Variable Gravity During Parabolic Flight
AU: * Jones, S B
EM: scott.jones@usu.edu
AF: Utah State University, Dept. Plants, Soils and Climate, Logan, UT 84322-4820, United States
AU: Heinse, R
EM: heinse@cc.usu.edu
AF: Utah State University, Dept. Plants, Soils and Climate, Logan, UT 84322-4820, United States
AU: \v{S}imunek, J
EM: jiri.simunek@ucr.edu
AF: University of California, Riverside, Department of Environmental Sciences, Riverside, CA 92521, United States
AU: Tuller, M
EM: mtuller@cals.arizona.edu
AF: The University of Arizona, Department of Soil, Water & Environmental Science, Tucson, AZ 85721, United States
AU: Or, D
EM: dani.or@epfl.ch
AF: Ecole Polytechnique Federale de Lausanne, Laboratory of Soil and Environmental Physics, Lausanne, 1015, Switzerland
AB: Parabolic flight experiments were conducted to study effects of reduced gravity on multiphase fluid distribution and transport. Notwithstanding the limited duration of microgravity (~20 s), measurements of porous-media fluid behavior have been successful in demonstrating significant differences between μ- and 1-g. Further understanding of reduced gravity effects can be gained through numerical modeling of hydrodynamic data. The gravitational acceleration during parabolic flight cycles between hypergravity (1.8-g) and microgravity (~10^-6-g). Impacts of variable gravity on measurements focusing on the microgravity portion of the flight were ambiguous and difficult to interpret. One-dimensional numerical modeling using the Richards equation with a variable gravity term was compared with matric potential and water content measurements obtained during several parabolic flights. Introducing a time-dependent variable gravity term facilitated modeling of the hypergravity phase, which extends to 1.8-g and precedes each microgravity cycle. This ‘complete' treatment of flight data allowed more accurate modeling of secondary water retention scanning curves. This is important because during parabolic flight, wetting and draining processes occur simultaneously in different volumes of the porous medium. Both baked clay aggregates and glass beads were packed into containers with heights varying from 1 to 7 cm. Hydrostatic and matric potentials were measured using micro-tensiometers and water content was determined either volumetrically or using TDR. Hydrus-1D was used to model the hydrodynamics with time- dependent gravity input in sub-second increments of time. Our results suggest that the impact of a preceding hypergravity-phase on microgravity hydrodynamics during parabolic flight should not be ignored and requires due attention for adequate modeling of matric potential and water content measurements in porous media.
DE: 1847 Modeling
DE: 1865 Soils (0486)
DE: 1866 Soil moisture
DE: 1875 Vadose zone
DE: 1899 General or miscellaneous
SC: Hydrology [H]
MN: 2007 Fall Meeting