Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session S09: Industrial Applications: General |
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Chair: Dana Grecov, University of British Columbia Room: 213 |
Tuesday, November 26, 2019 10:31AM - 10:44AM |
S09.00001: Aerodynamic Performance of a Rim Driven Thruster Maxwell Kogler, Conor Pace, Hasan Raza, Michael Vu, Oleg Goushcha Rim driven thruster consists of a fan actuated into a rotational motion by a mechanism located at its outer radius, rather than by a centerline shaft as seen in conventional fan designs. Such configuration eliminates a need for a centerline hub containing driving mechanism, allowing for an undisturbed core flow of fluid through the centerline region of the fan. In this study we present a rim driven thruster actuated by an interaction between electric and magnetic fields, similar to the brushless motor with entire fan and supporting structure resembling rotor and stator, respectfully. This thruster operates in air and can be used as a propulsion system in airplanes. The aerodynamic performance was evaluated experimentally by measuring upstream and downstream velocity fields and thrust forces at various flight conditions. Results from the experiments are compared to the predictions made by the Blade Element Theory. [Preview Abstract] |
Tuesday, November 26, 2019 10:44AM - 10:57AM |
S09.00002: Effect of surface roughness on numerical modeling of full-scale self-propulsion Henrik Mikkelsen, Jens Honore Walther When predicting the full-scale performance of a vessel, the resistance from surface roughness is important, since it can account for up to $15\, \%$ of the total resistance for a newly built vessel. We compare full-scale computational fluid dynamics (CFD) simulations with speed trial measurement from six sister ro-ro vessels. The study includes extensive validation and verification of both resistance, open-water and self-propulsion simulations. Full-scale resistance and open water as well as model scale self-propulsion simulations show good agreement with towing tank measurements and predictions. However, the full-scale self-propulsion simulations using the traditional approach of including the roughness estimated by the empirical formula of Townsin significantly underestimates the power from the speed trials. By including the effect of hull and propeller roughness directly into the CFD simulation, by modifying the wall functions, the discrepancy between CFD and speed trial measurements now reach an acceptable level. As a result, full-scale CFD simulations is becoming a viable and accurate alternative to transitional towing tank experiments. [Preview Abstract] |
Tuesday, November 26, 2019 10:57AM - 11:10AM |
S09.00003: Thermal mapping of Hollow Cathodes to model the thermal loads of Iodine Ion Propulsion Paul Winner Iodine possesses desirable qualities that could make it a potential fuel of choice in future space missions requiring ion propulsion, potentially replacing Xenon; if the thruster can have similar endurance despite Iodine's corrosiveness. A computer-aided design model of a hollow cathode with a Lanthanum Hexaboride insert was created in Solidworks, using its thermal load simulator to generate an approximate temperature model of it in operation. Data was then collected to refine the model by getting temperature readings of a hollow cathode in operation by attaching type K thermocouples to the outside and inside of the hollow cathode and firing it in a vacuum chamber. Differences between the thermal model and the experimental data will be discussed in addition to the assumptions made within the thermal model. Based on the data, the hollow cathode is far below expected temperatures, though there are several sources of error to explain this discrepancy. [Preview Abstract] |
Tuesday, November 26, 2019 11:10AM - 11:23AM |
S09.00004: Electrohydrodynamics of charge-injecting high-voltage electrodes Xuewei Zhang In liquid dielectrics, initiation of electrical breakdown usually takes place at the electrode/liquid interface under a much lower electric field than that required by molecular ionization, even if the material is highly purified. One of the main causes is the fact that there exist micro-protrusions and micro-pores on the electrode surface. Smart use of charge injection to improve electrical breakdown strength has been demonstrated in previous works. The objective of this paper is to propose and numerically study a new design of charge injecting electrodes inspired by inkjet printer. In a needle-plane configuration, the needle electrode is hollow and has microchannels connecting its interior to the outside, both filled with the same dielectric liquid. The highly inhomogeneous electric field has electrostriction effect, creating a low-pressure region at the needle tip. The pressure difference across the microchannels will drive liquid flow from inside the electrode to the outside. During this, the liquid jets will be electrified and carrying the charge with the same sign as the electrode (homocharge). We build the electrohydrodynamic model and develop a numerical program to simulate this process. The steady-state simulation results confirm that the hollow electrode with microchannels can effectively inject homocharges which enhance the electrical conductivity and lower the electric field in the region near the electrode surface. [Preview Abstract] |
Tuesday, November 26, 2019 11:23AM - 11:36AM |
S09.00005: Modelling Purification of Flue Gas in Porous Catalytic Media Kristian Kiradjiev, Chris Breward, Ian Griffiths, Donald Schwendeman, Uwe Beuscher, Vasudevan Venkateshwaran In this talk, we present a mathematical model for flue-gas purification in a porous filter with catalyst. In particular, we consider a device that converts gaseous sulphur dioxide into liquid sulphuric acid which accumulates, causing clogging. Using the theory of homogenisation, we develop a multiscale model that takes into account local properties of the filter to describe the overall device operation. We explore the effect of changing various dimensionless parameters on the filter efficiency. We also consider asymptotic reductions to the full system and compare them with full numerical solutions. [Preview Abstract] |
Tuesday, November 26, 2019 11:36AM - 11:49AM |
S09.00006: Enhancement of convective cooling in solar photovoltaics Marc Calaf, Brooke Stanislawski, Todd Harman, Raul B. Cal At present, most research on solar photovoltaics (PV) is focused on improving cell efficiency at 25\textordmasculine C, where most world-record efficiencies have been measured, and which neglects the fact that in outdoor conditions the air temperature grows significantly higher. Reduction of undesirable thermal effects can be achieved by either decreasing heat generation at the cell level or by increasing heat dissipation. Here, heat dissipation is exploited through enhanced convection, which has remained fairly unexplored. It is now well-accepted that solar module temperature increases lead to undesired power losses. The rate of efficiency decrease per degree of temperature rise is quantified by the ``temperature coefficient.'' For a silicon cell, the efficiency of the cell drops by about 0.4{\%} with the increase of every one degree Celsius above 25\textordmasculine C, and solar modules in real atmospheric conditions can typically operate at upwards of 25\textordmasculine C above the ambient temperature. While ongoing efforts continue to reduce the thermal losses at the source, manipulation the operating temperatures of solar PV modules is sought out within large-scale solar farms by developing new solar farm arrangements that boost the convective heat transfer between the modules and the atmospheric flow. For this purpose, large-eddy simulations of realistic solar PV farms are conducted, where results will illustrate whether there exists any preferential solar farm arrangement for enhanced cooling and hence increased solar PV efficiency. [Preview Abstract] |
Tuesday, November 26, 2019 11:49AM - 12:02PM |
S09.00007: Effect of moving ground and rotating wheels on the flow over a high speed passenger train Mohammad Asif Sultan, Dibyendu Konar, Subhransu Roy High speed passenger trains are gradually coming up successfully as a mode of modern transportation. The impact of moving ground and rotating wheels on the flow around a high speed train has been numerically investigated. A Reynolds number of 1.85x10$^{\mathrm{6}}$ based on the air flow velocity and height of the train is used in the CFD modelling using \textit{k-epsilon} turbulence model. The total aerodynamic drag were calculated for the three cases: stationary ground, moving ground, moving ground with rotating wheels. Moving ground boundary condition is found to eliminate the boundary layer near the ground which affects the flow beneath the train and changes the pressure distribution. The rotating wheel boundary condition tends to increase the velocity of flow in the bogie region. With moving ground, there is 10.2{\%} increment in the total drag which further increases by 1{\%} when rotating wheels are considered. The simulations show that bogies also have a major contribution on the total drag. It is around 15.2{\%} with stationary ground, increases to 22.8{\%} while ground is moving and finally attains 25.1{\%} when the most realistic case of both moving ground and wheel rotation is considered. [Preview Abstract] |
Tuesday, November 26, 2019 12:02PM - 12:15PM |
S09.00008: Enhanced Power for a New Design of Savonius Rotors Abdelkader Filali, Omar Matar, Hamza Semmari, Adel Boumaaraf, Khaoula Zitouni, Lyes Khezzar The present work involves the investigation and improvement of the performance of a vertical Savonius rotor. This study is based on numerical simulation of the aerodynamic behaviour of different proposed rotor designs. An exhaustive literature review allowed us to identify the influential parameters and helped us to conclude that the power of the Savonius rotor can be significantly improved by a careful and judicious choice of these parameters. The numerical approach was first validated with experimental and numerical studies previously published in the literature for the case of a semi-circular blade rotor (conventional). Then, an improvement process based on the modification of the blades profile to an elliptical shape was adopted. A second improvement of the Savonius rotor is conducted by introducing new air collectors of different aerodynamic profiles referred to here as `Model I’ and `Model II’. All these geometrical considerations and propositions have made it possible to define an optimal geometrical configuration. [Preview Abstract] |
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