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 M35: Energy: Applications |
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Chair: Mark Calaf, University of Utah Room: 2001A |
Tuesday, November 25, 2014 8:00AM - 8:13AM |
M35.00001: A two-dimensional potential flow model of the interaction of a vortex ring passing over a flexible plate for energy harvesting applications JiaCheng Hu, Sean Peterson Recent advancements in highly deformable smart materials have lead to increasing interest in small-scale energy harvesting research for powering low consumption electronic devices. One such recent experimental study by Goushcha et al. (APL, 2014) explored energy harvesting from a passing vortex ring by a cantilevered smart material plate oriented parallel to, and offset from, the path of the ring in an otherwise quiescent fluid. The present study focuses on modeling this experimental study using potential flow. The problem is modeled in two dimensions with the vortex ring represented as a pair of counter-rotating free vortices. Vortex parameters are determined to match convection speed of the ring and its pressure loading on the beam. The plateis approximated as a Kirchhoff-Love plate, and represented as a finite length vortex sheet in the fluid domain. The analytical model matches the experimentally measured strain at the clamped end of the beam well, suggesting that the model can be used as a tool to optimize this energy harvesting configuration. Results of a parametric study will be presented, as well as a discussion of the range of parameters for which the model is a good representation of the physical system. [Preview Abstract] |
Tuesday, November 25, 2014 8:13AM - 8:26AM |
M35.00002: CFD Aided Design and Optimization of Francis Turbine Runners Fatma Ayancik, Gizem Demirel, Kutay Celebioglu, Erdem Acar, Selin Aradag Francis turbines are commonly used for hydroelectric power plants with their wide range of flow rate and head values. They are composed of five main components and they generate energy with the help of the runner connected to the generator. Therefore, runner is the most important part of a Francis turbine. All components of turbines are linked and they are designed to maximize the turbine efficiency. The dimensions of the runner vary depending on the design discharge, head and the speed of the rotor of the generators. In this study, a design methodology is developed to design turbine runners with the help of computational fluid dynamics and is applied to the runner design of three different hydroelectric power plant turbines. Multi objective design optimization is also performed and the response surfaces are investigated to obtain maximum turbine efficiency and cavitation free design. [Preview Abstract] |
Tuesday, November 25, 2014 8:26AM - 8:39AM |
M35.00003: The effectiveness of a heated air curtain Daria Frank Air curtains are high-velocity plane turbulent jets which are installed in the doorway in order to reduce the heat and the mass exchange between two environments. The air curtain effectiveness $E$ is defined as the fraction of the exchange flow prevented by the air curtain compared to the open-door situation. In the present study, we investigate the effects of an opposing buoyancy force on the air curtain effectiveness. Such an opposing buoyancy force arises for example if a downwards blowing air curtain is heated. We conducted small-scale experiments using water as the working fluid with density differences created by salt and sugar. The effectiveness of a downwards blowing air curtain was measured for situations in which the initial density of the air curtain was less than both the indoor and the outdoor fluid density, which corresponds to the case of a heated air curtain. We compare the effectiveness of the heated air curtain to the case of the neutrally buoyant air curtain. It is found that the effectiveness starts to decrease if the air curtain is heated beyond a critical temperature. Furthermore, we propose a theoretical model to describe the dynamics of the buoyant air curtain. Numerical results obtained from solving this model corroborate our experimental findings. [Preview Abstract] |
Tuesday, November 25, 2014 8:39AM - 8:52AM |
M35.00004: Optimization of Transient Heat Exchanger Performance for Improved Energy Efficiency Gabriela Bran Anleu, Pirouz Kavehpour, Adrienne Lavine, Richard Wirz Heat exchangers are used in a multitude of applications within systems for energy generation, energy conversion, or energy storage. Many of these systems (e.g. solar power plants) function under transient conditions, but the design of the heat exchangers is typically optimized assuming steady state conditions. There is a potential for significant energy savings if the transient behavior of the heat exchanger is taken into account in designing the heat exchanger by optimizing its operating conditions in relation to the transient behavior of the overall system. The physics of the transient behavior of a heat exchanger needs to be understood to provide design parameters for transient heat exchangers to deliver energy savings. A numerical model was used to determine the optimized mass flow rates thermal properties for a thermal energy storage system. The transient behavior is strongly linked to the dimensionless parameters relating fluid properties, the mass flow rates, and the temperature of the fluids at the inlet of each stream. Smart metals, or advanced heat exchanger surface geometries and methods of construction will be used to meet the three goals mentioned before: 1) energy and cost reduction, 2) size reduction, and 3) optimal performance for all modes of operation. [Preview Abstract] |
Tuesday, November 25, 2014 8:52AM - 9:05AM |
M35.00005: Numerical study of finned heat pipe-assisted latent heat thermal energy storage system Saeed Tiari, Songgang Qiu, Mahboobe Mahdavi In the present study the thermal characteristics of a finned heat pipe-assisted latent heat thermal energy storage system are investigated numerically. A transient two dimensional finite volume based model employing enthalpy-porosity technique is implemented to analyze the performance of a thermal energy storage unit with square container and high melting temperature phase change material. The effects of heat pipe spacing, fin length and numbers as well as the influence of natural convection on the thermal response of the thermal energy storage unit have been studied. The obtained results reveal that the natural convection has considerable effect on the melting process of the phase change material. Increasing the number of heat pipes leads to the increase of melting rate and the decrease of base wall temperature. Also, the increase of fin length results in the decrease of temperature difference within the phase change material in the container, providing more uniform temperature distribution. Furthermore, it is showed that the number of fins does not affect the performance of the system considerably. [Preview Abstract] |
Tuesday, November 25, 2014 9:05AM - 9:18AM |
M35.00006: Low-dimensional model of mixing in a liquid metal battery Douglas Kelley Adding large-scale energy storage to Earth's electrical grids would accommodate demand variations, enhance grid stability, and enable broad deployment of wind and solar generation. Liquid metal batteries are currently being commercialized as a promising and economically viable technology for grid-scale storage. Mass transport by mixing in their all-liquid electrodes affects battery performance, so predicting flow from known operating conditions (battery current and temperature) would allow for improved battery design. But accurate numerical simulation of these turbulent, three-dimensional, multi-phase flows, including electromagnetic forces and phase change, is challenging and computationally expensive. I will discuss a method for using experimental measurements to construct a simplified low-dimensional model with the potential to predict flow and battery performance. Initial results will also be presented. [Preview Abstract] |
Tuesday, November 25, 2014 9:18AM - 9:31AM |
M35.00007: Hydrothermal Gasification for Waste to Energy Brenden Epps, Mark Laser, Yeunun Choo Hydrothermal gasification is a promising technology for harvesting energy from waste streams. Applications range from straightforward waste-to-energy conversion (e.g. municipal waste processing, industrial waste processing), to water purification (e.g. oil spill cleanup, wastewater treatment), to biofuel energy systems (e.g. using algae as feedstock). Products of the gasification process are electricity, bottled syngas (H2 + CO), sequestered CO2, clean water, and inorganic solids; further chemical reactions can be used to create biofuels such as ethanol and biodiesel. We present a comparison of gasification system architectures, focusing on efficiency and economic performance metrics. Various system architectures are modeled computationally, using a model developed by the coauthors. The physical model tracks the mass of each chemical species, as well as energy conversions and transfers throughout the gasification process. The generic system model includes the feedstock, gasification reactor, heat recovery system, pressure reducing mechanical expanders, and electricity generation system. Sensitivity analysis of system performance to various process parameters is presented. A discussion of the key technological barriers and necessary innovations is also presented. [Preview Abstract] |
Tuesday, November 25, 2014 9:31AM - 9:44AM |
M35.00008: Large eddy simulation of turbulent diffusion flame with hybrid fuel of CH4/H2 in various background conditions Sungmin Hong, Wook Lee, Han Ho Song, Seongwon Kang A turbulent diffusion flame with hybrid fuel of methane and hydrogen is analyzed to investigate the effects of operating conditions on flame shape, rate of fuel consumption and pollutant formation. Various combinations of operating parameter, i.e. hydrogen concentration, background pressure and temperature, are examined in relatively high pressure and temperature conditions that can be found at the end of compression stroke in an internal combustion engine. A flamelet-progress variable approach (FPVA) and a dynamic subgrid scale (SGS) model are used for large eddy simulation (LES). A comparison with previous experiments and simulations in the standard condition shows a good agreement in the statistics of flow fields and chemical compositions, as well as in the resultant trends by similar parametric studies. As a result, the effects of added hydrogen are found to be consistent for most of the chemical species in the range of background pressure and temperature conditions. However, the flow fields of some species such as OH, NO, CO at a higher pressure and temperature state show a behavior different from the standard condition. Finally, hydrogen addition is shown to improve flame stability which is measured by the pressure fluctuations in all the tested conditions. [Preview Abstract] |
Tuesday, November 25, 2014 9:44AM - 9:57AM |
M35.00009: A Non-linear Lifting Line Model for Design and Analysis of Trochoidal Propulsors Bernard Roesler, Brenden Epps Flapping wing propulsors may increase the propulsive efficiency of large shipping vessels. A comparison of the design of a notional propulsor for a large shipping vessel with (a) a conventional ducted propeller versus (b) a flapping wing propulsor is presented. Calculations for flapping wing propulsors are performed using an open-source MATLAB software suite developed by the authors, CyROD, implementing an unsteady lifting-line model with free vortex wake roll-up to study the non-linear effects of foil-wake, and foil-foil interactions. Improvements to the traditional lifting line theory are made using further discretization of the wake vortex ring spacing near the trailing edge. Considerations of packaging options for a flapping wing propulsor on a large shipping vessel are presented, and compared with those for a conventional ducted propeller. [Preview Abstract] |
Tuesday, November 25, 2014 9:57AM - 10:10AM |
M35.00010: An Experimental Investigation on the Wake Characteristics behind Dual-Rotor Wind Turbines Zhenyu Wang, Ahmet Ozbay, Wei Tian, Anupam Sharma, Hui Hu We report an experimental study to investigate the aeromechanics and wake characteristics of dual-rotor wind turbines (DRWTs) with co- and counter-rotating configurations, in comparison to those of a conventional single-rotor wind turbine (SRWT). The experiments were performed in a large-scale Aerodynamic/Atmospheric Boundary Layer (AABL) wind tunnel under neutral stability conditions. In addition to measuring the power output performance of DRWT and SRWT systems, static and dynamic wind loads acting on the SRWT and DRWT systems were also investigated. Furthermore, a high resolution PIV system was used for detailed wake flow field measurements (free-run and phase-locked) so as to quantify the characteristics of the turbulent turbine wake flow and to quantitatively visualize the transient behavior of the unsteady vortex structures in the wakes of DRWTs, in comparison with those behind a conventional SRWT systems. The detailed flow field measurements are correlated with the dynamic wind loads and power output measurements to elucidate underlying physics for higher total power yield and better durability of the wind turbines. [Preview Abstract] |
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