Bulletin of the American Physical Society
67th Annual Meeting of the APS Division of Fluid Dynamics
Volume 59, Number 20
Sunday–Tuesday, November 23–25, 2014; San Francisco, California
Session A24: Industrial Applications I |
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Chair: Michele Guala, University of Minnesota Room: 2003 |
Sunday, November 23, 2014 8:00AM - 8:13AM |
A24.00001: Study of Hydrokinetic Turbine Arrays with Large Eddy Simulation Danny Sale, Alberto Aliseda Marine renewable energy is advancing towards commercialization, including electrical power generation from ocean, river, and tidal currents. The focus of this work is to develop numerical simulations capable of predicting the power generation potential of hydrokinetic turbine arrays--this includes analysis of unsteady and averaged flow fields, turbulence statistics, and unsteady loadings on turbine rotors and support structures due to interaction with rotor wakes and ambient turbulence. The governing equations of large-eddy-simulation (LES) are solved using a finite-volume method, and the presence of turbine blades are approximated by the actuator-line method in which hydrodynamic forces are projected to the flow field as a body force. The actuator-line approach captures helical wake formation including vortex shedding from individual blades, and the effects of drag and vorticity generation from the rough seabed surface are accounted for by wall-models. This LES framework was used to replicate a previous flume experiment consisting of three hydrokinetic turbines tested under various operating conditions and array layouts. Predictions of the power generation, velocity deficit and turbulence statistics in the wakes are compared between the LES and experimental datasets. [Preview Abstract] |
Sunday, November 23, 2014 8:13AM - 8:26AM |
A24.00002: Wingtip Devices for Marine Hydrokinetic Turbines Ivaylo Nedyalkov, Jesse Shull, Ian Gagnon, John Brindley, Martin Wosnik Wingtip devices have become widely used in aircraft and wind turbine applications. There are only a few examples of their usage on Marine Hydrokinetic Turbines (MHK), which have only recently been developed to utility scale. Novel wingtip devices were designed for use specifically in marine applications, to reduce wingtip vortex induced drag and with the additional considerations for suppressing tip vortex cavitation and avoiding significant bio-fouling. A reference foil, a generic wingtip, and new wingtip designs were studied numerically using OpenFOAM, and some of the wingtips (including the reference foil and the generic wingtip) were studied experimentally in the University of New Hampshire High-Speed Water Tunnel. The experimental test bed was designed specifically for this study and can accommodate various wingtips which extend to the center of the tunnel. Lift and drag were measured for different angles of attack and cavitation inception was studied. Additionally, pressure was recorded at 4 locations on each tip. The pressure ports were also used for mass injection studies. [Preview Abstract] |
Sunday, November 23, 2014 8:26AM - 8:39AM |
A24.00003: Inducer Performance with Varying Inlet Blade Angles with a Stability Control Device Ryan Lundgreen, Daniel Maynes, Kerry Oliphant, Steve Gorrell High suction performance pumps use an inducer as the first stage of the pump to limit the amount of cavitation within the rest of the machine. Suction performance improves significantly when inducers are operated at low flow coefficients. Small blade angles are required at low flow coefficients to maintain a stable operation, however, they are more prone to cavitation blockage and are less robust structurally. It has been shown that a stability control device has a significant stabilizing effect on the flow through an inducer, particularly at low flow coefficients. A local increase in the mass flow rate at the leading edge of the inducer allows the blade to operate at the design flow coefficient regardless of the mass flow rate through the machine. This allows inducers with a greater inlet blade angle, which are less prone to cavitation blockage and can be more structurally robust, to maintain stable operation at low flow coefficients. Numerical simulations were conducted on four different inducers that implemented the stability control device, with inlet blade angles ranging from 7 to 14 degrees. Analysis from the results has led to significant insights into how changes in the inlet blade angle affect the physics and performance of the stability control device. [Preview Abstract] |
Sunday, November 23, 2014 8:39AM - 8:52AM |
A24.00004: Effects of the geometry of the exit of a tube in an oscillating flow Elia Echeverr\'Ia, Carlos M\'alaga, Steven Czitrom, Arturo Olvera, Catalina Stern The problem of optimizing the performance of a wave-driven seawater pump --comprising a resonant duct and an exhaust duct joined by a variable volume air-compression chamber-- it is explored by studying oscillating flows at the exit of a tube. It is known that the performance of this pump depends on the geometry of the mouth of its intake tube. An inspection of the integral expression of the Navier-Stokes equation along a central streamline of this flow shows that changing the shape of the tube's mouth modifies only the inertia and energy losses terms because both depend on the flow field at the chosen streamline. These changes must be such that the integral relation is preserved. Therefore, by measuring the inertial term (known as added mass), the term for losses can be measured indirectly. We developed a method to measure the added mass for oscillating flows in tubes with different mouth shapes and compared these measurements with those obtained for a model of the flow through the pump. Our results suggest a way to find a criterion for choosing the geometry of the mouth of the tubes in order to minimize dissipation and improve efficiency of the pump. [Preview Abstract] |
Sunday, November 23, 2014 8:52AM - 9:05AM |
A24.00005: A Method for Turbocharging Four-Stroke Single Cylinder Engines Michael Buchman, Amos Winter Turbocharging is not conventionally used with single cylinder engines due to the timing mismatch between when the turbo is powered and when it can deliver air to the cylinder. The proposed solution involves a fixed, pressurized volume -- which we call an air capacitor -- on the intake side of the engine between the turbocharger and intake valves. The capacitor acts as a buffer and would be implemented as a new style of intake manifold with a larger volume than traditional systems. This talk will present the flow analysis used to determine the optimal size for the capacitor, which was found to be four to five times the engine capacity, as well as its anticipated contributions to engine performance. For a capacitor sized for a one-liter engine, the time to reach operating pressure was found to be approximately two seconds, which would be acceptable for slowly accelerating applications and steady state applications. The air density increase that could be achieved, compared to ambient air, was found to vary between fifty percent for adiabatic compression and no heat transfer from the capacitor, to eighty percent for perfect heat transfer. These increases in density are proportional to, to first order, the anticipated power increases that could be realized. [Preview Abstract] |
Sunday, November 23, 2014 9:05AM - 9:18AM |
A24.00006: A Novel Pressure Compensating Valve for Low-Cost Drip Irrigation Amos Winter, Alexander Wiens Nearly one billion people are currently living as subsistence farmers in the developing world. Irrigation could drastically increase quality of life for these individuals by enabling them to grow more and higher value crops. However, current irrigation technologies are too costly for this economic sector, particularly in off-grid applications. The cost of an off-grid irrigation system is primarily driven by the power required to pump the water at a relatively high pressure (> 1 bar). We propose a novel pressure compensating drip emitter design which allows these systems to operate at 1/10 the pressure of current products, making them economically viable in developing markets. Our proposed solution is inspired by the resonating nozzle of a deflating balloon. We use a reduced order model to understand the physical principles which drive the cyclic collapse of the balloon nozzle. This knowledge is applied to propose a pressure compensating drip emitter consisting of a simple compliant tube in series with a rigid conical diffuser. A scaling analysis is performed to determine the ideal geometry of the system and the model is applied to demonstrate that the proposed design is capable of pressure compensation in the required operation range. Preliminary experiments are presented. [Preview Abstract] |
Sunday, November 23, 2014 9:18AM - 9:31AM |
A24.00007: ABSTRACT WITHDRAWN |
Sunday, November 23, 2014 9:31AM - 9:44AM |
A24.00008: Airborne Detection and Tracking of Geologic Leakage Sites Jamey Jacob, Rakshit Allamraju, Allan Axelrod, Calvin Brown, Girish Chowdhary, Taylor Mitchell Safe storage of CO$_2$ to reduce greenhouse gas emissions without adversely affecting energy use or hindering economic growth requires development of monitoring technology that is capable of validating storage permanence while ensuring the integrity of sequestration operations. Soil gas monitoring has difficulty accurately distinguishing gas flux signals related to leakage from those associated with meteorologically driven changes of soil moisture and temperature. Integrated ground and airborne monitoring systems are being deployed capable of directly detecting CO$_2$ concentration in storage sites. Two complimentary approaches to detecting leaks in the carbon sequestration fields are presented. The first approach focuses on reducing the requisite network communication for fusing individual Gaussian Process (GP) CO$_2$ sensing models into a global GP CO$_2$ model. The GP fusion approach learns how to optimally allocate the static and mobile sensors. The second approach leverages a hierarchical GP-Sigmoidal Gaussian Cox Process for airborne predictive mission planning to optimally reducing the entropy of the global CO$_2$ model. Results from the approaches will be presented. [Preview Abstract] |
Sunday, November 23, 2014 9:44AM - 9:57AM |
A24.00009: 3D Finite Element Formulation of Nonlinear Partial-slip Condition on Curved Geometries Onkar Sahni, Farhad Behafarid, Lauren Fovargue For many fluid flow problems, the behavior of the fluid at the physical boundaries doesn't adhere to the traditional no-slip condition or perfect-slip law and exhibits a partial slip. This partial-slip behavior can be nonlinear. Additionally for real geometries of interest, physical boundaries are composed of arbitrary 3D curved surfaces. In this study we focus on a finite-element formulation that includes 3D nonlinear partial-slip condition on general curved surfaces. Using this formulation, we perform finite-element analysis of flow problems with such a nonlinear boundary condition. We present convergence studies on canonical problems and also include cases with complex curved surfaces. [Preview Abstract] |
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