HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Heinse, R. Articles by Or, D. Search for Related Content PubMed Articles by Heinse, R. Articles by Or, D. GeoRef GeoRef Citation Agricola Articles by Heinse, R. Articles by Or, D. Related Collections Macroporous/Aggregated Media Variably Saturated Fluid Flow Soil Physics

Measurements and Modeling of Variable Gravity Effects on Water Distribution and Flow in Unsaturated Porous Media

^a Dep. of Plants, Soils and Climate, Utah State Univ., Logan, UT 84322-4820
^b Universities Space Research Assoc., Mail Code EC3, NASA/JSC, Houston, TX 77058
^c Dep. of Soil, Water & Environmental Science, The Univ. of Arizona, Tucson, AZ 85721
^d Lab. of Soil and Environmental Physics, Ecole Polytechnique Fédérale de Lausanne, Switzerland

View larger version (15K): [in this window] [in a new window]   FIG. 1. Steady-state water retention curves measured in 1 g for porous ceramic aggregates (a) Profile (0.25–1 mm), (b) Mix (0.25–2 mm), and (c) Turface (1–2 mm). Solid lines represent the van Genuchten water retention model (Eq. [2]) fitted to six replicate measurements of drainage (•) and wetting () for processes within interaggregate pores. Dashed and dotted lines indicate the 95% confidence interval for the fitted retention curves.

View larger version (37K): [in this window] [in a new window]   FIG. 2. (a) 1-cm water retention cell with pressure transducer connected to a porous cup embedded in, and in hydraulic contact with, the porous media. The porous cup was connected to a syringe pump that provided metered water addition and removal. (b) 2-cm water retention cell with (1) water inlet connected to sintered porous plate, (2) water outlet, pressure transducer ports, and centered time domain reflectometer (TDR) probe. (c) 4-cm water retention cell showing the vertical location of the two TDR probes. (d) 7-cm cell showing the pressure transducer positions and water inlet/outlet.

View larger version (62K): [in this window] [in a new window]   FIG. 3. Saturated hydraulic conductivity cells showing the pressure transducer locations. The water inlet was connected to a syringe pump for constant water fluxes using a bidirectional feed. The water outlet was connected to a collapsible reservoir.

View larger version (19K): [in this window] [in a new window]   FIG. 4. Hypothetical diagram of the equilibrium distribution of water content and matric potentials in a 4-cm-tall sample of porous ceramic aggregate Turface subjected to (a) Earth's gravity, (b) 1.8 g, and (c) 0 g. The average matric potential (i.e., at the midpoint) is constant at –4 cm. The shaded area shows regions of validity for water content and potentials where the gravitational force scales the hydrostatic equilibrium distribution.

View larger version (16K): [in this window] [in a new window]   FIG. 5. (a) Dependence of static Bond numbers Bos on the normalized gravity force considering the pore scale and system/sample scale influence of gravity vs. capillarity. Solid lines represent porous ceramic aggregate Turface; dashed lines represent Profile. (b) Characteristic time scales for cell heights of 1 and 7 cm after Eq. [6], respectively.

View larger version (35K): [in this window] [in a new window]   FIG. 6. Measured and modeled matric potentials as a response to variable gravity in the 7-cm cell for porous ceramic aggregate Profile. Figures on the left side (b–e) show measured matric potentials for three observation heights at z = 1, 3, and 5 cm (Fig. 2) as a function of time for different water contents , where (a) depicts the gravitational acceleration and change in aircraft cabin pressure for plot (b). Figures on the right side compare measured (lines) and simulated (symbols) matric potentials in microgravity following hypergravity (g–j). In (f), measured normalized gravitational accelerations are depicted for measurements shown in (g).

View larger version (24K): [in this window] [in a new window]   FIG. 7. Comparison of quasi-steady-state microgravity (µg) drainage and wetting water retention and steady-state 1-g porous media water retention for Profile, Turface, and a mixture of these obtained in the 1-cm cell. The solid lines are predicted 1-g retention curves (upper = drainage, lower = wetting). Dashed or dotted lines indicate the 95% confidence interval for the 1-g retention curves. Indicated water contents are shown as average sample values determined from pumping volumes. Matric potentials were measured at z = 0.5 cm.

View larger version (26K): [in this window] [in a new window]   FIG. 8. Comparison of quasi-steady-state microgravity drainage and wetting water retention data with steady-state 1-g porous media water retention curves for Turface. In (a) measurements in a 2- cm-tall sample with water contents shown as average sample values determined from pumped volumes are shown. Matric potentials were measured at z = 0.5 and 1 cm. Measurements using a 4-cm-tall sample with water contents shown as TDR measurements are depicted in (b) and (c), where water contents were measured at z = 1 cm (bottom) and z = 3 cm (top), respectively. The solid lines are predicted 1-g retention curves (upper = drainage, lower = wetting). Dashed or dotted lines indicate the 95% confidence interval for the 1-g retention curves.

View larger version (25K): [in this window] [in a new window]   FIG. 9. Dynamic matric potential-water content response measured in Turface in the 4-cm cell during two consecutive parabolas at two vertical locations (z = 1 and 3 cm, bottom and top, respectively). Five mL of water was added in the 1.8-g period in-between the parabolas with a syringe pump. Solid lines indicate the 1-g wetting and drainage water retention curves. Dotted lines indicate scaled water response curves for 1.8-g. Solid symbols (•) indicate 1.8-g, and open-faced symbols () indicate microgravity-measured data.

View larger version (25K): [in this window] [in a new window]   FIG. 10. Saturated-flow pressure gradients as a function of hydraulic flux for glass beads (GB), Profile, and Turface measured in variable gravity. Error bars indicate the standard deviation, while solid lines denote the mean saturated hydraulic conductivity.