The effects of various wetting conditions and aperture sizes on water flow and slip in a parallel‐walled fracture were investigated. Water flow experiments showed that a larger slip occurred as the surface became more hydrophobic. For a creosote‐wetted surface of the fracture with an aperture of 508 μm, the increase in the water flow rate due to the slip was as much as 10.0% compared to that in a water‐wetted surface. Similarly to a water‐wetted surface, no slip took place at a gasoline‐wetted surface, which was weakly hydrophobic. The slip lengths, a notional distance from the wall to a point inside the wall where fluid velocity extrapolates to zero, for light oil‐ and creosote‐wetted surfaces were constant over a range of flow velocities in the laminar flow regime. The study indicates that no slip boundary condition‐based equations are not adequate for quantifying water flow through NAPL‐wetted fractures.
A heterogeneous nature of rough-walled rock fractures complicates a recovery of DNAPL trapped in fractured rock aquifers, which forms a persistent plume within the fractured rocks and present a long-term source of contamination. Experimental studies were conducted to suggest a criterion for the physical displacement of DNAPL from rough-walled fractures in the context of capillary number (N ca ), a dimensionless number representing the ratio of the viscous to capillary forces. A series of experiments using water, surfactant solution and dense fluid were conducted in the range of capillary number from 2.29 × 10 -4 to 3.41 × 10 -2 . The experimental results suggested that a higher capillary number than 1 × 10 -2 be required for a near complete DNAPL removal (more than 95% of initial saturation) from rough-walled fractures. For capillary number on the order of 10 -3 , DNAPL can be mobilized or recovered to some degree. For the capillary number below 1 × 10 -3 , any kind of remedial fluids would have no effect on physical displacement. It is suggested that remedial fluid utilizing physical displacement be formulated to comply with N ca > 1 × 10 -2 to maximize a complete physical removal and the fluid utilizing chemical solubilization or reaction do with N ca < 1 × 10 -3 to minimize unwanted migration.
Alignment tolerance for EO/IR airborne camera using common optic is an important factor in stabilization accuracy and geo-pointing accuracy. Before airborne camera is mounted on the aircraft, defining alignment tolerance and verification of it is essential in production as well as research and development. In this paper we establish basic concept on the definition and elements of alignment tolerance for airborne camera and propose how to measure each of those elements. Components and the measurement sequence of alignment tolerance are as follows: 1) tolerance of alignment between EO and IR LOS. 2) tolerance of sensor alignment. 3) tolerance of position reporting accuracy. 4) tolerance of mount alignment
Unsaturated hydraulic conductivity of the bentonite-buffer was evaluated using the relative humidity data. The method for calculating unsaturated hydraulic conductivity was deduced from the general analytical equation representing the movement of water in unsaturated media, which was applied to the experimental results of water infiltration tests for identifying the behavior of unsaturated hydraulic conductivity according to the water saturation. Unlike the saturated condition, the hydraulic gradient and water flux were irregularly changed, and the unsaturated hydraulic conductivity was increased with increasing the experimental time. Swelling of bentonite grains due to the water absorption increased the volume and size of pore within bentonite, resulting in the increase of water velocity and unsaturated hydraulic conductivity. This result suggested the necessity of further investigation on the correlation between the swelling degree of bentonite-buffer and unsaturated hydraulic conductivity. The method used in this study can be useful technique for evaluating long-term hydraulic performance of bentonite-buffer in the radioactive waste disposal system.
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