Infiltration into inclined fibrous sheets

The flow from line and point sources through an inclined fibrous sheet is studied experimentally and theoretically for wicking from a saturated region and flow from a constant-flux source. Wicking from a saturated line generates a wetted region whose length grows diffusively, linearly or tends to a constant, depending on whether the sheet is horizontal or inclined downwards or upwards. A constant-flux line source generates a wetted region which ultimately grows linearly with time, and is characterized by a capillary fringe whose thickness depends on the relative strength of the source, gravitational and capillary forces. Good quantitative agreement is observed between experiments and similarity solutions.Capillary-driven and constant-flux source flows issuing from a point on a horizontal sheet generate a wetted patch whose radius grows diffusively in time. The flow is characterized by the relative strength of the source and spreading induced by the action of capillary forces, gamma. As gamma increases, the fraction of the wetted region which is saturated increases. Wicking from a saturated point corresponds to gamma = gamma(c), and spreads at a slower rate than from a line source. For gamma < gamma(c), the flow is partially saturated everywhere. Good agreement is observed between measured moisture profiles, rates of spreading, and similarity solutions.Numerical solutions are developed for point sources on inclined sheets. The moisture profile is characterized by a steady region circumscribed by a narrow boundary layer across which the moisture content rapidly changes. An approximate analytical solution describes the increase in the size of the wetted region with time and source strength; these conclusions are confirmed by numerical calculations. Experimental measurements of the downslope length are observed to be slightly in excess of theoretical predictions, though the dependence on time, inclination and flow rate obtained theoretically is confirmed. Experimental measurements of cross-slope width are in agreement with numerical results and solutions for short and long times. The affect of a percolation threshold is observed to ultimately arrest cross-slope transport, placing a limitation on the long-time analysis

A comparison of the observed behaviors with the expressed opinions of a group of pediatric nurses toward mothers who live in the hospital with their children.

Thesis (M.S.)--Boston Universit

Analysis of Fiber UV Degradation Through an Environmental Chamber

Environmentally degraded fibers could impact multiple aspects of a fiber comparison, considering that collected weathered fabrics/fibers may express an altered chemical structure and/or colorimetric property compared to their unexposed counterparts. Depending on the amount of degradation the evidence has suffered, it could be challenging for forensic scientists to make conclusions from their comparative analyses. Observations presented in this study were orchestrated to test the possible outcomes that sunlight has on fabric-based materials. Photodegradation of fabrics was investigated through the use of an environmental chamber for a duration of six weeks, which would be equivalent to three months of real-world UV exposure. Red and blue fabrics of 100% polyester, nylon, and cotton were tested; purity and identity of each sample were confirmed by polarized light microscopy and Fourier-transform infrared spectroscopy. Colorimetric properties were analyzed through fluorescence microscopy. Accelerated weathering was accomplished in an environmental chamber, fabrics were subjected to repeated cycles—two hours at an irradiance of 0.25 w/m2, two hours at 0.47 w/m2, four hours at 0.68 w/m2, two hours at 0.47 w/m2, and lastly two hours at 0.25 w/m2—of UV light (340nm) for 1,008 hours. Relative humidity (\u3c 25%), air temperature (25°C), and black panel temperature (35°C) were programmed to be held constant for the whole duration of the experiment. All exposed fibers either lost all pigment completely or were a faded variation of the original dyed color. Fluorescence microscopic analysis of the blue and red nylon fibers, as well as the red polyester fibers, all revealed substantially varied results between the UV-degraded and their counterparts. In addition, UV-exposed synthetic fibers were found to be more textured, which could have resulted from a reaction between the light and the particles of TiO2 and polymer. This observation should be further studied. Overall, results presented within this study suggest that the UV-exposed fiber would be assumed as a different fiber when compared to its counterpart. Considering that this study mimicked the methods commonly performed by forensic personnel, this conclusion presents a threat for cases with evidentiary fiber samples from both indoor and outdoor conditions.https://scholarscompass.vcu.edu/uresposters/1451/thumbnail.jp

Numerical study of flow through and around a circular array of cylinders

This paper describes a study of the local and global effect of an isolated group of cylinders on an incident uniform flow. Using high resolution two-dimensional computations, we analysed the flow through and around a localised circular array of cylinders, where the ratio of array diameter (D-G) to cylinder diameter (D) is 21. The number of cylinders varied from N-C = 7 to 133, and they were arranged in a series of concentric rings to allow even distribution within the array with an average void fraction phi = N-C(D/DG)(2), which varied from 0.016 to 0.30. The characteristic Reynolds number of the array was Re-G = 2100. A range of diagnostic tools were applied, including the lift/drag forces on each cylinder (and the whole array), Eulerian and Lagrangian average velocity within the array, and the decay of maximum vorticity with distance downstream. To interpret the flow field, we used vorticity and the dimensionless form of the second invariant of the velocity gradient tensor. A mathematical model, based on representing the bodies as point forces, sources and dipoles, was applied to interpret the results. Three distinct flow regimes were identified. For low void fractions (phi 0.15), the array generates a wake in a similar way to a solid body of the same scale. For low void fraction arrays, the mathematical model provides a reasonable assessment of the forces on individual bodies within the array, the Eulerian mean velocity and the upstream velocity field. While it broadly captures the change in the rate of decay of the maximum vorticity magnitude Omega(max) downstream, the magnitude is underpredicted

An integrated study of parallel valveless micropumps

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.We describe an analytical, computational and experimental study of parallel valveless micropumps. A one dimensional model of a parallel micropump is presented and compared with available experimental data. The model confirms the linear decrease of the volume flux with pressure rise which is consistent with the experiments. The computational study showed a similar linear decrease but highlighted the effect of turbulence closures on the rectified mean flow, with the experimental data sitting between the turbulent and laminar closure regimes. The experimental study confirmed the importance of the displacement distance of fluid through the nozzle compared to nozzle length in the setting whether the flow regime is streaming or rectified. General conclusions are made about how to improve the pumping efficiency of micropumps.This study is supported by the Dorothy Hodgkin Postgraduate Award (DHPA) of the Engineering and Physical Sciences Research Council (EPSRC) of United Kingdom and Ebara Research Co. Ltd of Japan

Arrival direction distribution of cosmic rays of energy 10 (18) eV

The Haverah Park air-shower experiment recorded over 8500 events with primary energy 10 to the 18th power eV between 1963 and 1983. An analysis of these events for anisotropies in celestial and galactic coordinates is reported. No very striking anisotropies are observed

Injection of gaseous hydrogen into a natural gas pipeline

The injection of pure hydrogen at a T-junction into a horizontal pipe carrying natural gas is analysed computationally to understand the influence of blending and pipe geometry (diameter ratio, various 90° orientations) on mixing, for a target of 4.8–20% volume fraction hydrogen blend. The strongly inhomogeneous distribution of hydrogen within the pipe flow and on the pipe walls could indicate the location of potential pipe material degradation including embrittlement effects. The low molecular mass of hydrogen reduces the penetration of a side-branch flow and increases the buoyancy forces leading to stratification with high hydrogen concentrations on the upper pipe surface, downstream of the branch. Top-side injection leads to the hydrogen concentration remaining >40% for up to 8 pipe diameters from the injection point for volumetric dilutions ( D) less than 30%. Under-side injection promotes mixing within the flow interior and reduces wall concentration at the lower surface, compared to top-side injection. The practical implications for these results, in terms of mixing requirements and the contrasting constraint of codes of practice and energy demands, are discussed

Somali Bibliography --2012

A bibliography of resources arranged alphabetically and published before 2012

Somali Bibliography by Keyword --2012

A bibliography of resources organized by topical keyword and published before 2012