Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Fluid Dynamics
Volume 56, Number 18
Sunday–Tuesday, November 20–22, 2011; Baltimore, Maryland
Session H9: Industrial Applications |
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Chair: Hamid Rahai, California State University, Long Beach Room: 312 |
Monday, November 21, 2011 10:30AM - 10:43AM |
H9.00001: Investigations of the Effects of Distortion on Trajectory of Diesel Particulate Matter (PM) Hamid Rahai Exposures to diesel PM within urban areas have resulted in elevated respiratory illnesses and risk of premature cardiac death. The present investigation is part of our continuous efforts to understand the relationship between diesel exhausts concentrations and local urban aerodynamics, in metropolitan areas where significant diesel vehicle activities are present. Wind tunnel experiments and field tests were performed to understand the effects of distortion caused by building structures on trajectory of the diesel PM, emitted from diesel engine exhausts in cross flows. Our previous similar investigations without distortion have shown a linear decay in PM concentration with a 10 percent slope. However, when the structures were present, PM concentration increased significantly up to 1d upstream of the object, before it decreases due to the blockage effect. A mathematical correlation based on experimental data has been proposed to estimate the concentration of the diesel PM with respect to the wind velocity at different distances upstream of the objects. [Preview Abstract] |
Monday, November 21, 2011 10:43AM - 10:56AM |
H9.00002: Feature formation in the planar-flow melt spinning of metals linked to meniscus unpinning Anthony Altieri, Paul Steen In the planar-flow melt spinning of metals (PFMS), liquid metal is brought into contact with a cold, rotating wheel and thin ribbon is spun off. A unique characteristic of the PFMS process is the narrow gap region between the nozzle, where liquid metal is introduced, and the wheel, which allows for the formation of a liquid ``puddle'' held in place by surface tension. The flow behavior in the puddle can have a dramatic effect on the appearance of the thin ribbon product. In particular, thickness depressions which span the width of the ribbon appear periodically under certain casting conditions. These features are related to puddle vibrations of the air-liquid meniscus which forms upstream of the fluid inlet. A lower frequency (1 kHz) feature previously has been related to Rayleigh oscillations of a drop. We report that a higher frequency (10 kHz) feature, also dependent on Rayleigh oscillations, depends additionally on the translation speed of the substrate, as seen by correlation. This difference is related to meniscus pinning/unpinning and flow structures within the puddle. A model of fluid flow which connects these two features and a discussion of these differences will be presented. [Preview Abstract] |
Monday, November 21, 2011 10:56AM - 11:09AM |
H9.00003: Design and characterization of an aerodynamic shoe sampling system for screening trace explosive materials Matthew Staymates, Greg Gillen, Jessica Grandner, Stefan Lukow As part of an ongoing effort with the Transportation Security Laboratory, the National Institute of Standards and Technology has been developing a prototype shoe sampling system that relies on aerodynamic sampling as the primary mechanism for liberating, transporting, and collecting explosive contamination. This presentation will focus on the fluid dynamics associated with the current prototype design. This design includes several air jets and air blades that are used to dislodge particles from target areas of a shoe. A large blower then draws air and liberated particles into a collection device at several hundred liters per second. Experiments that utilize optical particle counting techniques have shown that the applied shear forces from these jets are capable of liberating particles efficiently from shoe surfaces. Results from real-world contamination testing also support the effectiveness of air jet impingement in this prototype. Many examples of flow visualization will be shown. The issues associated with air spillage, particle release efficiency, and particle transport will also be discussed. [Preview Abstract] |
Monday, November 21, 2011 11:09AM - 11:22AM |
H9.00004: Numerical simulation of a cross flow Marine Hydrokinetic turbine. Taylor Hall, Alberto Aliseda In the search for alternative sources of energy, the kinetic energy of water currents in oceans, rivers and estuaries is being explored as predictable and environmentally benign. We are investigating the flow past a cross flow turbine in which a helical blade under hydrodynamic forces turns around a shaft perpendicular to the free stream. This type of turbine, while very different from the classical horizontal axis turbine commonly used in the wind energy field, presents advantages for stacking in very narrow constricted channels where the water currents are consistently high and therefore turbine installation may be economically feasible. We use a model of a helical four-bladed turbine in cross flow to investigate the efficiency of the energy capture and the dynamics of the turbulent wake. Scale model experiments in a flume are used to validate the numerical results on a stationary configuration as an initial step towards creating an accurate numerical model of the turbine. The simulation of the rotating turbine provides a full perspective on the effect of angular position on flow detachment and vortex shedding from the blade, as well as on the fluctuations of the shaft torque produced (a problematic feature of this type of turbine). The results are analyzed in terms of hydrodynamic optimization of the blade and its structural loading. [Preview Abstract] |
Monday, November 21, 2011 11:22AM - 11:35AM |
H9.00005: Investigation of Helical Cross-Flow Axis Hydrokinetic Turbines, Including Effects of Waves and Turbulence Peter Bachant, Martin Wosnik A new test bed for hydrokinetic turbines was used to evaluate different cross-flow axis turbines, and investigate effects of waves and turbulence. Turbine thrust (drag) and mechanical power were measured in a tow tank with cross section 3.7 x 2.4m at speeds of 0.6-1.5 m/s for a Gorlov Helical Turbine (GHT) and a Lucid spherical helical turbine (LST). GHT performance was also measured in progressive waves of various periods, grid turbulence, and in a cylinder wake. Overall, the GHT performs with higher power and thrust coefficients than the LST. A 2nd law, or kinetic exergy efficiency, defined as the fraction of kinetic energy removed from the flow that is converted to usable shaft work, was measured. The distribution of energy into shaft work and turbulent kinetic energy in the wake can affect environmental transport processes and performance of turbines arrays. Progressive waves generally enhance performance of the GHT, but can lead to stall at higher tip speed ratios compared to the steady case. Grid turbulence delays dynamic stall and enables operation at lower tip speed ratios, while not decreasing maximum power coefficient. Performance in a cylinder wake is highly dependent on the cylinder's cross-stream location, ranging from benign to detrimental. The experimental observations provide insight into the physical principles of operation of cross-flow axis turbines. [Preview Abstract] |
Monday, November 21, 2011 11:35AM - 11:48AM |
H9.00006: Applying Turbulence Models to Hydroturbine Flows: A Sensitivity Analysis Using the GAMM Francis Turbine Bryan Lewis, John Cimbala, Alex Wouden Turbulence models are generally developed to study common academic geometries, such as flat plates and channels. Creating quality computational grids for such geometries is trivial, and allows stringent requirements to be met for boundary layer grid refinement. However, engineering applications, such as flow through hydroturbines, require the analysis of complex, highly curved geometries. To produce body-fitted grids for such geometries, the mesh quality requirements must be relaxed. Relaxing these requirements, along with the complexity of rotating flows, forces turbulence models to be employed beyond their developed scope. This study explores the solution sensitivity to boundary layer grid quality for various turbulence models and boundary conditions currently implemented in OpenFOAM. The following models are resented: k-omega, k-omega SST, k-epsilon, realizable k-epsilon, and RNG k-epsilon. Standard wall functions, adaptive wall functions, and sub-grid integration are compared using various grid refinements. The chosen geometry is the GAMM Francis Turbine because experimental data and comparison computational results are available for this turbine. [Preview Abstract] |
Monday, November 21, 2011 11:48AM - 12:01PM |
H9.00007: Numerical Simulations of Marine Hydrokinetic (MHK) Turbines Using the Blade Element Momentum Theory Teymour Javaherchi, Oskar Thulin, Alberto Aliseda Energy extraction from the available kinetic energy in tidal currents via Marine Hydrokinetic (MHK) turbines has recently attracted scientists' attention as a highly predictable source of renewable energy. The strongest tidal resources have a concentrated nature that require close turbine spacing in a farm of MHK turbines. This tight spacing, however, will lead to interaction of the downstream turbines with the turbulent wake generated by upstream turbines. This interaction can significantly reduce the power generated and possibly result in structural failure before the expected service life is completed. Development of a numerical methodology to study the turbine-wake interaction can provide a tool for optimization of turbine spacing to maximize the power generated in turbine arrays. In this work, we will present numerical simulations of the flow field in a farm of horizontal axis MHK turbines using the Blade Element Momentum Theory (BEMT). We compare the value of integral variables (i.e. efficiency, power, torque and etc.) calculated for each turbine in the farm for different arrangements with varying streamwise and lateral offsets between turbines. We find that BEMT provides accurate estimates of turbine efficiency under uniform flow conditions, but overpredicts the efficiency of downstream turbines when they are strongly affected by the wakes. [Preview Abstract] |
Monday, November 21, 2011 12:01PM - 12:14PM |
H9.00008: Injection pumps William Schultz, Bosuk Han, Eric Johnsen Injection pumps are simple devices with no moving parts but with complex flow including free-shear and boundary layers combined with shocks and possible multiphase flow. In spite of this, they are susceptible to simple control volume analyses. Here, we examine the extent to which these analyses represent optimal performance for a steam injector. We develop performance measures for 2D RANS computations and experiments. [Preview Abstract] |
Monday, November 21, 2011 12:14PM - 12:27PM |
H9.00009: Spray Characterization of Gas-to-Liquid Synthetic Jet Fuels Kumaran Kannaiyan, Reza Sadr In the recent years, development of alternative jet fuels is gaining importance owing to the demand for cleaner combustion. In addition to having energy density that matches those of conventional fuels, alternate jet fuels need to possess vital qualities such as rapid atomization and vaporization, quick re-ignition at high altitude, less emission, and poses ease of handling. The fuel preparatory steps (atomization and vaporization) and mixing in a combustion chamber play a crucial role on the subsequent combustion and emission characteristics. Gas-to-Liquid (GTL) synthetic jet fuel obtained from Fischer-Tropsch synthesis has grabbed the global attention due to its cleaner combustion characteristics as a result of the absence of aromatics and sulphur. As a part of an on-going joint effort between Texas A{\&}M at Qatar (TAMUQ), Rolls-Royce (UK), and German Aerospace Laboratory (DLR), a spray characterization experimental facility is set up at TAMUQ to study the spray characteristics of GTL fuel and highlights the influence of change in fuel composition on the spray characteristics. In this work, spray characteristics such as droplet size, velocity, and distribution of different GTL fuel blends is investigated and compared with the spray characteristics of conventional JetA1 fuel. [Preview Abstract] |
Monday, November 21, 2011 12:27PM - 12:40PM |
H9.00010: Removal of resist film from wafer surface by steam-water mixture jet Takashi Mashiko, Toshiyuki Sanada, Itsuo Nishiyama, Hideo Horibe We have shown that the steam-water mixture jet, a two-fluid jet with its carrier gas being steam, exhibits high cleaning performance when sprayed onto a target. This is a promising technique which requires only simple apparatus and little or no chemicals, but the cleaning mechanism remains unknown. We have conducted a series of experiments to elucidate the mechanism and learn how to meet given industrial requirements (e.g., set parameters for desired detergency). In our recent experiment, we adopted a resist-coated silicon wafer as the target and evaluated the jet performance of resist removal from the wafer. The removal performance proved to be a decreasing function of the resist hardness and of the resist-wafer adhesivity, and an increasing function of the jet duration. These results suggest that the resist removal by the steam-water mixture jet mainly consists of physical processes (e.g., peel-off process), in contrast to the traditional resist-removal techniques utilizing chemical reactions. [Preview Abstract] |
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