Academic literature on the topic 'COMSOL Thin-Film Flow module'
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Journal articles on the topic "COMSOL Thin-Film Flow module"
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Alvarado-Rolon, O., R. Natividad, R. Romero, L. Hurtado, and A. Ramírez-Serrano. "Modelling and Simulation of the Radiant Field in an Annular Heterogeneous Photoreactor Using a Four-Flux Model." International Journal of Photoenergy 2018 (2018): 1–16. http://dx.doi.org/10.1155/2018/1678385.
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This work focuses on modeling and simulating the absorption and scattering of radiation in a photocatalytic annular reactor. To achieve so, a model based on four fluxes (FFM) of radiation in cylindrical coordinates to describe the radiant field is assessed. This model allows calculating the local volumetric rate energy absorption (LVREA) profiles when the reaction space of the reactors is not a thin film. The obtained results were compared to radiation experimental data from other authors and with the results obtained by discrete ordinate method (DOM) carried out with the Heat Transfer Module of Comsol Multiphysics® 4.4. The FFM showed a good agreement with the results of Monte Carlo method (MC) and the six-flux model (SFM). Through this model, the LVREA is obtained, which is an important parameter to establish the reaction rate equation. In this study, the photocatalytic oxidation of benzyl alcohol to benzaldehyde was carried out, and the kinetic equation for this process was obtained. To perform the simulation, the commercial software COMSOL Multiphysics v. 4.4 was employed.
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Tappura, Kirsi, and Kaarle Jaakkola. "A Thin-Film Thermoelectric Generator for Large-Area Applications." Proceedings 2, no. 13 (December 10, 2018): 779. http://dx.doi.org/10.3390/proceedings2130779.
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A thin-film thermoelectric generator (TEG) applying a novel folded design where both the heat flux and current flow are in the plane of the thin-film is presented. The performance of the first fabricated devices is demonstrated and the results compared with the computational ones. The produced power is analyzed against the power requirements of a wireless sensor node and it is shown that a thermoelectric module of the area of <1 m2 consisting of the novel TEG units is able to power a wireless sensor node of various sensors applicable e.g., to environmental monitoring of a building. The integration of energy-autonomous sensors for multifunctional smart windows providing the required temperature gradient is anticipated.
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Esman, A. K., G. L. Zykov, V. A. Potachits, and V. K. Kuleshov. "Simulation of Thin-Film Solar Cells with a CuInSe2 Chalcopyrite Structure." ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 63, no. 1 (February 7, 2020): 5–13. http://dx.doi.org/10.21122/1029-7448-2020-63-1-5-13.
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By using numerical simulation, the operating temperatures of a thin-film solar cell based on CuInSe2 have been determined and the solar radiation density values, at which stabilization of the temperature operating conditions of the thin-film solar cell is not required, have been optimized. The maximum possible efficiency value of ~14.8 % is achieved under actual operating conditions, and is maintained by the incoming thermal energy as both emitted in this cell and infrared radiation of the sun and the environment. A model of the proposed thin-film solar cell was implemented in the COMSOL Multiphysics program environment with the use of the Heat Transfer Module. The operating temperatures of the solar cell without thermal stabilization under conditions of the diurnal and seasonal variations of both the ambient temperature and the power density of the AM1.5 solar spectrum have been determined. The maximum value of this power density was varied from 1.0 to 500 kW/m2 when using concentrators. The obtained values of operating temperatures of the thin-film solar cell were used to determine its main parameters in the SCAPS-1D program. The graphs of the operating temperature, efficiency and fill factor of the thin-film solar cell versus the solar radiation density are provided. It is shown that in order to obtain the highest possible efficiency of a solar cell, it is necessary to use concentrated solar radiation with a power density, the maximum value of which should be 8 kW/m2 in July and 10 kW/m2 in January. In the case of lower and higher values of power density, an appropriate thermal stabilization of the cell under consideration is necessary. The dependencies of efficiency, fill factor and open-circuit voltage versus the stabilization temperature of the solar cell, temperature gradients at the interfaces of the thermoelectric layer were also calculated. It is shown that by choosing optimal values of the thermal stabilization, the efficiency of the proposed solar cell may be about 15 % or more.
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Esman, A. K., V. K. Kuleshov, V. A. Potachits, and G. L. Zykov. "Simulation of Tandem Thin-Film Solar Cell on the Basis of CuInSe2." ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 61, no. 5 (October 4, 2018): 385–95. http://dx.doi.org/10.21122/1029-7448-2018-61-5-385-395.
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CuInSe2 thin-film solar cells are promising materials for photovoltaic devices. One of the main tasks of researchers is to find ways to increase the solar cells efficiency. In this paper we propose an original structure of a thin-film solar cell based on a tandem connection of a photoelectric converter and a thermoelectric layer based on CuInSe2. The photoelectric converter consists of CuInSe2 and CdS layers. A 3D model of the proposed thin-film solar cell was implemented in the COMSOL Multiphysics environment with using the Heat Transfer module. The simulation was carried out taking into account the diurnal and seasonal variations of both the ambient temperature and the power density of the AM1.5 solar spectrum for the geographical coordinates of Minsk. The solar radiation power density of about 500 kW/m2 can be achieved by using concentrators. The temperature pattern and temperature gradients are calculated in each layer of the solar cell without and with the temperature stabilization of the substrate back side as well as without and with the thermal insulation of the substrate ends. Graphs of the temperature gradients of the thermoelectric layer and the temperature variations of the photoelectric converter of the solar cell are given. As a result of the simulation, it is shown how the uneven heating of both the surface of a thin-film solar cell and its layers occur under conditions of diurnal and seasonal variations of both the ambient temperature and the solar radiation power density. Under concentrated solar radiation exposure, the photoelectric converter surface can be heated up to 700 °C without temperature stabilization of the solar cell substrate. The operating temperature of the photoelectric converter was maintained at no more than 2.35 °C in January and at no more than 14.23 °C in July due to the temperature stabilization of the substrate back side of the proposed device. This made it possible to achieve an increase in the output power of the solar cell both by summing the photoand thermoelectric output voltages and by the concentration of solar radiation.
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Hernández Sebastián, Natiely, Noé Villa Villaseñor, Francisco-Javier Renero-Carrillo, Daniela Díaz Alonso, and Wilfrido Calleja Arriaga. "Design of a Fully Integrated Inductive Coupling System: A Discrete Approach Towards Sensing Ventricular Pressure." Sensors 20, no. 5 (March 10, 2020): 1525. http://dx.doi.org/10.3390/s20051525.
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In this paper, an alternative strategy for the design of a bidirectional inductive power transfer (IPT) module, intended for the continuous monitoring of cardiac pressure, is presented. This new integrated implantable medical device (IMD) was designed including a precise ventricular pressure sensor, where the available implanting room is restricted to a 1.8 × 1.8 cm2 area. This work considers a robust magnetic coupling between an external reading coil and the implantable module: a three-dimensional inductor and a touch mode capacitive pressure sensor (TMCPS) set. In this approach, the coupling modules were modelled as RCL circuits tuned at a 13.56 MHz frequency. The analytical design was validated by means of Comsol Multiphysics, CoventorWare, and ANSYS HFSS software tools. A power transmission efficiency (PTE) of 94% was achieved through a 3.5 cm-thick biological tissue, based on high magnitudes for the inductance (L) and quality factor (Q) components. A specific absorption rate (SAR) of less than 1.6 W/Kg was attained, which suggests that this IPT system can be implemented in a safe way, according to IEEE C95.1 safety guidelines. The set of inductor and capacitor integrated arrays were designed over a very thin polyimide film, where the 3D coil was 18 mm in diameter and approximately 50% reduced in size, considering any conventional counterpart. Finally, this new approach for the IMD was under development using low-cost thin film manufacturing technologies for flexible electronics. Meanwhile, as an alternative test, this novel system was fabricated using a discrete printed circuit board (PCB) approach, where preliminary electromagnetic characterization demonstrates the viability of this bidirectional IPT design.
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Kumar, Nallapaneni Manoj, Umashankar Subramaniam, Mobi Mathew, A. Ajitha, and Dhafer J. Almakhles. "Exergy analysis of thin-film solar PV module in ground-mount, floating and submerged installation methods." Case Studies in Thermal Engineering 21 (October 2020): 100686. http://dx.doi.org/10.1016/j.csite.2020.100686.
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Lu, Hsueh-Tsung, Yutao Qin, and Yogesh Gianchandani. "A Microvalve Module with High Chemical Inertness and Embedded Flow Heating for Microscale Gas Chromatography." Sensors 21, no. 2 (January 18, 2021): 632. http://dx.doi.org/10.3390/s21020632.
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This paper reports a multi-valve module with high chemical inertness and embedded flow heating for microscale gas chromatography (µGC) systems. The multi-valve module incorporates a monolithically microfabricated die stack, polyimide valve membranes, and solenoid actuators. The design incorporates three valves within a single module of volume 30.2 cm3, which is suitable for the small form factor of µGC systems. The die stack uses fused silica wafers and polyimide valve membranes that enhance chemical inertness. The monolithic die stack requires only three lithographic masks to pattern fluidic microchannels, valve seats, and thin-film metal heaters and thermistors. The performance of fabricated multi-valve modules is compared to a commercial valve in tests using multiple volatile organic compounds, including alkanes, alcohols, ketones, aromatic hydrocarbons, and phosphonates. The valves show almost no distortion of chromatographic peaks. The experimentally measured ratio of flow conductance is 3.46 × 103, with 4.15 sccm/kPa in the open state and 0.0012 sccm/kPa in the closed state. The response time is <120 ms.
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Pa, P. S. "A Reclamation System via a Pins-Module Tool for Touch Sensing Material Surfaces." Applied Mechanics and Materials 372 (August 2013): 321–24. http://dx.doi.org/10.4028/www.scientific.net/amm.372.321.
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This study demonstrates a designed pins-module tool and a precise reclamation system using a micro electroremoval process for sensing material of tin-doped indium oxide thin-films dissolved from a surface of polyethylene terephthalate of touch-panel. In the current experiment, a higher dissolution rate of the defective tin-doped indium oxide corresponds to high rotational speed of the cylinders tool with large flow rate of the electrolyte. A small diameter of the anode or a small diameter of the cathode combined with enough electric power, results in fast dissolution. The removal rate of tin-doped indium oxide thin-film is improved by decreasing the cylinders number. Importantly, the performance of a designed pins-module tool was found to be more effective in the micro electroremoval process. It requires only a short period of time to dissolve the nanostructured of tin-doped indium oxide easily and cleanly.
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Shinde, Anil B., and Prashant M. Pawar. "Effect of partial grooving on the performance of hydrodynamic journal bearing." Industrial Lubrication and Tribology 69, no. 4 (July 10, 2017): 574–84. http://dx.doi.org/10.1108/ilt-06-2016-0124.
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Purpose This study aims to improve the performance of hydrodynamic journal bearings through partial grooving on the bearing surface. Design/methodology/approach Bearing performance analysis is numerically carried out using the thin film flow physics of COMSOL Multiphysics 5.0 software. Initially, the static performance analysis is carried out for hydrodynamic journal bearing system with smooth surface, and the results of the same are validated with results from the literature. In the later part of the paper, the partial rectangular shape micro-textures are modeled on bearing surface. The effects of partial groove pattern on the bearing performance parameters, namely, fluid film pressure, load carrying capacity, frictional power loss and frictional torque, are studied in detail. Findings The numerical results show that the values of maximum fluid film pressure, load carrying capacity, frictional power loss and frictional torque are considerably improved due to deterministic micro-textures. Bearing surface with partial groove along 90°-180° region results in 81.9 per cent improvement in maximum fluid film pressure and 75.9 per cent improvement in load carrying capacity as compared with smooth surface of journal bearing, with no increase in frictional power loss and frictional torque. Maximum decrease in frictional power loss and frictional torque is observed for partially grooving along 90°-360° region. The simulations are supported by proof-of-concept experimentation. Originality/value This study is useful in the appropriate selection of groove parameters on bearing surface to the bearing performance characteristics.
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Menzler, N. H., F. Han, T. van Gestel, W. Schafbauer, F. Schulze-Küppers, S. Uhlenbruck, W. A. Meulenberg, and H. P. Buchkremer. "Development of Thin-Film Manufacturing Technologies for Solid Oxide Fuel Cells and Gas Separation Membranes." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2012, CICMT (September 1, 2012): 000277–80. http://dx.doi.org/10.4071/cicmt-2012-wa12.
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The development of solid oxide fuel cells (SOFCs) and gas separation membranes for fossil (fuel?) power plants has previously suffered from cost issues like the manufacturing of the core components including i) the ceramic fuel cell and ii) the ceramic membrane, and from insufficient power density (current density or flow rate) on the stack, module or system level. Forschungszentrum Jülich has been working on SOFC development for 20 years, and on membrane development for 6 years. Both energy-related applications are based on similar materials systems, similar micro-structural features (porous-dense, coarse-fine), comparable application parameters (e.g. high temperature) and are manufactured with similar technologies. In the past the focus laid mostly on basic materials research and proving the functionality of the membranes or fuel cells. Meanwhile, one key topic has been the application of low-cost thin-film high-throughput manufacturing technologies. This includes the fabrication of the supports (mostly tape-casting), the coating with functional layers by ceramics technologies (screen printing, roll coating) and the reduction of sintering steps and temperatures. Additionally special thin-film technologies like sol-gel technique and electron beam evaporation / sputtering have also been applied for functional layers, depending on the functional necessities. The presentation gives an overview regarding the state-of-the-art in SOFC and gas separation membrane development at Forschungszentrum Jülich with an emphasis on the manufacturing technologies, resulting in optimized layer micro-structures and thickness. Additionally it summarizes the electrochemical and permeation data obtained so far.
Dissertations / Theses on the topic "COMSOL Thin-Film Flow module"
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Brhlík, Rostislav. "MKP simulace elastohydrodynamického kontaktu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231788.
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This diploma thesis deals with an application of the finite element method on elastohydrodynamic (EHD) lubrication simulations. Commercially available software COMSOL is used for the computation, while two different modules for modeling EHD lubrication are described in a detail. Firstly, a new approach using the module Thin-Film Flow is developed, considering and describing some limitations of this approach. This is the very first published work dealing complex with EHD simulation in Thin-Film Flow module. In the second part of the thesis, there was created a model of line contact using the module for the introduction of partial differential equations (PDE). The model is partially verified with available works for different values of the input parameters. Subsequently, the velocity effect of the contact surfaces on the pressure and the lubricant thickness in contact is analyzed. Finally, the last part is examines the influence of the values of some parameters on the final value of the contact pressure and the lubricant thickness, as well as on numerical stability of the entire model.
Conference papers on the topic "COMSOL Thin-Film Flow module"
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Abyaneh, M. H. J., and M. H. Saidi. "Velocity Distributions in (r,θ) Directions for Laminar Flow of a Film Around Horizontal Circular Tube." In ASME 2006 2nd Joint U.S.-European Fluids Engineering Summer Meeting Collocated With the 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/fedsm2006-98087.
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Velocity distributions in (r,θ) directions are evaluated by solving simultaneous simplified Navier-Stokes equations (NSE) and continuity equation (CE) in polar coordinate. The analysis is based on steady state laminar flow of thin falling liquid film on a horizontal circular tube, for cases in which traction on the film surface is considered negligible. It is a common geometry for part of engineering problems such as evaporator, condenser, absorber, generator of absorption chillers and other similar units in mechanical and chemical engineering. Knowledge of the velocity profiles is usually needed for: 1- solving governing energy and species equations 2- estimating the average and film surface velocity, and 3- evaluating film thickness distribution and its gradient. Two models of velocity distributions are considered, namely actual model and simplified model. Models are compared not only with each other but also with semi actual model in (x,y) coordinate given in the literatures. The average and film surface velocity profiles and film thickness distribution for these models have been shown in various conditions. The results clearly show that the larger flow rates and/or smaller tube diameter increases the calculation error.
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Sakurai, Daisuke, Norihito Tsukahara, Kazuhiro Nishikawa, Takashi Akiguchi, Kazuto Nishida, Takaya Kobayashi, and Mari Saito. "Development of Film Module With Embedded Actives." In ASME 2003 International Electronic Packaging Technical Conference and Exhibition. ASMEDC, 2003. http://dx.doi.org/10.1115/ipack2003-35162.
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Since electric products need more effective features in terms of being compact, small, thin and highly performant, a new concept to create the advanced JISSO is required. We have invented the film module manufacturing process, in which the semiconductor is embedded into the thermo-elastic film and wired directly to exposed bumps. In this device, the fundamental process which is the embedded semiconductor into the thermoplastic film PETG, has been developed. This process is essential for the embedded active components film. This technique can be applied to packaging, memory cards, smart cards, flexible multi layer film and so on. The embedding process has the following problems; 1) Stud bumps on the IC may not appear on the surface of the film, 2) Voids may appear in the film during a high temperature press, 3) ICs may crack under high pressure. Subsequently, we solved the thermoplastic film’s flow process during the heat compression process using the rigid-plastic FEM (Finite Element method) analysis. We solved the resin temperature and load during the heat pressing process. It was discovered that ICs (0.18mm) could embed into the PETG film (0.2mm) within 13s. Finally, we applied this embedding process with the contactless IC card, which achieved a distance of calls of 100mm.
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Tichy, John, and Benyebka Bou-Sai¨d. "The PTT Model in Hip Joint Replacement: Shock Loading." In World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-63979.
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The Phan-Thien Tanner (PTT) model is one of the most widely used rheological models. It can properly describe all the common characteristics of viscoelastic non-Newtonian fluids. Synovial fluid of human joints, which also lubricates artificial joints, is well known to be highly viscoelastic. Thus it is reasonable to attempt to describe such joint behavior using non-Newtonian flow models. Modeling the geometry of the total hip replacement, the PTT model is applied in spherical coordinates to a thin confined fluid film. As an illustrative problem, the case of a sudden impulsive start of simple squeezing motion is solved, similar to landing on one’s feet after a vertical jump. The phenomena of shear thinning, stress relaxation, and stress overshoot are all exhibited.
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Pautsch, Adam G., and Timothy A. Shedd. "The Effects of Nozzle Configuration and Coolant Flow Rate on Spray Evaporative Cooling in a Multi-Chip Module Using FC-72." In ASME 2003 International Electronic Packaging Technical Conference and Exhibition. ASMEDC, 2003. http://dx.doi.org/10.1115/ipack2003-35227.
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With the power levels of computers constantly rising, the cooling of the die is becoming more challenging. One method of heat removal that can handle high heat fluxes and is still compact in size is Spray Evaporative Cooling (SEC). SEC, in this instance, uses arrays of nozzles to deliver a fluorinert cooling fluid, FC-72, to the die surface, and in the right conditions, a thin liquid film will form. This thin film allows for very high heat removal. Saturating the FC-72 with nitrogen enhances the effect. The characteristics of the spray greatly affect the behavior of the film. The critical heat flux (CHF), heat transfer coefficient of the system, and the variation in temperature on the die surface are important characteristics of an SEC system that must be considered. This study presents results of experiments performed to determine the effect of the number of spray nozzles on these quantities.
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Bacci, Alessandro, and Bruno Facchini. "Turbulence Modeling for the Numerical Simulation of Film and Effusion Cooling Flows." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27182.
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RANS simulations are known to suffer from serious deficiencies in the prediction of jet in a crossflow (JCF) because of the high complexity of this kind of flow. Particularly, the coherent structures resulting from the interaction of the two flow streams are characterized by a highly unsteady and anisotropic behavior which hardly stresses the hypotheses underling common eddy viscosity models (EVMs). Direct numerical simulation (DNS) and large eddy simulation (LES) methodologies are still excessively computationally intensive to be used as ordinary design tools. Therefore, the development of reliable RANS turbulence models for film cooling flows deserved a great deal of attention from the gas turbine community. Computations presented in this work were carried out using a modified k-ε turbulence model specifically designed for film cooling flows. The model, due to Lakehal et al., is based on the usage of an anisotropic eddy viscosity. The model has been implemented in the framework of a CFD commercial package through the user subroutine features. Computational model is developed following the suggestions of Walters and Leylek concerning the correct representation of the problem geometry and the location of the boundary conditions. The predictive capabilities of the model concerning the ability to capture the main flow structures as well as heat transfer features are investigated. Comparison of computed adiabatic effectiveness profiles with experimental measurements is provided in order to quantitatively validate the model. Results obtained with standard EVMs, particularly a two layer standard k-ε model, are also shown in order to reveal the improvements in the predictive capabilities resulting from the modified models.
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Zhu, Rui, Terrence W. Simon, and Gongnan Xie. "Numerical Predictions of Flow Structures and Film Cooling Effectiveness Values of a Turbine Vane: Effects of Secondary Holes." In ASME 2019 Heat Transfer Summer Conference collocated with the ASME 2019 13th International Conference on Energy Sustainability. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ht2019-3401.
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Abstract In modern gas turbines, film cooling is the most common and efficient way to provide thermal protection for hot components. Secondary holes to a primary film cooling hole are used to improve film cooling performance by creating anti-kidney vortices, a technique that has been well documented using flat plate models. This study aims to evaluate the effects of secondary holes on film cooling effectiveness over an airfoil. The film cooling performance and flow fields of a row of primary holes with secondary holes on the pressure side and suction side of a C3X vane are numerically investigated and compared with the results of a single row of cylindrical holes and two rows of staggered cylindrical holes. Cases with different blowing ratios are analyzed. It is shown from the simulation that film cooling effectiveness of primary holes with secondary holes is much better than with a single row of cylindrical holes, and slightly better than with two rows of staggered holes on both pressure side and suction side, with the same amount of coolant usage and blowing ratio. The enhancement is higher on the pressure side than on the suction side. The results show that adding secondary holes can enhance film cooling effectiveness by creating anti-kidney vortices, which will weaken jet lift-off from the primary holes caused by the kidney vortex pair, especially at higher blowing ratios. In addition, film coverage of primary holes with secondary holes is wider and persists further downstream than for a single row of cylindrical holes.
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Antunes, Manoella M., Cristiane Cozin, Fausto A. A. Barbuto, Rigoberto E. M. Morales, and Hendy T. Rodrigues. "Analysis of Slug Frequency Correlations for Two-Phase Gas-Liquid Horizontal Slug Flow." In ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fedsm2014-21672.
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Multiphase flows in pipelines show several flow patterns depending on the industrial applications where they appear. In oil and gas production, typical flow rates, geometries and the physical properties of the phases make slug flow to be the most common of all patterns. This kind of flow is characterized by an intermittent succession of an aerated liquid slug region and a long, turbulent gas bubble surrounded by a liquid film. Due to its complexity, slug flow modelling has been a challenge to many researchers over the last four decades. Presently, steady-state one-dimensional models based on the unit cell concept and more accurate physical representations based on either two-fluid or slug tracking models embedding transient flow capabilities are available. These models require closure relationships for predicting flow parameters. In the present work, a literature review on frequency correlations is presented. An analysis of the performance of those correlations with experimental data for horizontal slug flows was carried out and its results are presented.
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Milani, Pedro M., Julia Ling, Gonzalo Saez-Mischlich, Julien Bodart, and John K. Eaton. "A Machine Learning Approach for Determining the Turbulent Diffusivity in Film Cooling Flows." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-63299.
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In film cooling flows, it is important to know the temperature distribution resulting from the interaction between a hot main flow and a cooler jet. However, current Reynolds-averaged Navier-Stokes (RANS) models yield poor temperature predictions. A novel approach for RANS modeling of the turbulent heat flux is proposed, in which the simple gradient diffusion hypothesis (GDH) is assumed and a machine learning algorithm is used to infer an improved turbulent diffusivity field. This approach is implemented using three distinct data sets: two are used to train the model and the third is used for validation. The results show that the proposed method produces significant improvement compared to the common RANS closure, especially in the prediction of film cooling effectiveness.
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Poitras, Ge´rard J., Laurent-E. Brizzi, and Yves Gagnon. "Flow Over Model Buildings With Sloped Roofs." In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45518.
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The flow field around model buildings with different sloped roofs was investigated using Particle Image Velocimetry (PIV). The flow around model buildings having flat roofs was studied by many authors. Although buildings with sloped roofs are the most common type of low rise buildings, the flow around these buildings are not well known. Most of the studies for these types of buildings were made for the determination of surface pressures. The aim of this study is to highlight the fundamental differences between flat roofs and sloped roofs for three-dimensional obstacle flows. The experiments were performed in a wind tunnel having a cross section of 300 mm × 400 mm. All the models were 30 mm high (vertical wall) and were placed in a thin turbulent boundary layer. Three Reynolds numbers, based on the height of the obstacle, were used (12000, 22 000, 32 000). Furthermore, the quantitative data is analyzed and statistical results describing the mean and fluctuating velocity fields are presented. Finally, the surface pressures on the median plane were studied in order to correlate these pressures with the flow topology of different sloped roofs. It was found that upstream of the obstacle, the flow topology for the model having sloped roofs was similar to that of a flat roof apart from an increase in size of the well-known horseshoe vortex. However, the flow topology is not the same over different roofs, on the sides of the models and immediately downstream of the models. For the Reynolds number studied, there are no coherent flow structures over the upstream sloped roofs while an arch vortex is created on the sides of the models. This arch vortex is similar to the arch vortex that is created over a flat roof. An arch vortex is also present downstream of the models. The lower part of this vortex is similar to the one created for a flat roof. However, the upper part of the arch vortex starts from the tip of the roof and continues downstream and has an ellipse shape. This vortex also increases in size with the slope of the roof.
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San Andre´s, Luis, and Adolfo Delgado. "A Novel Bulk-Flow Model for Improved Predictions of Force Coefficients in Grooved Oil Seals Operating Eccentrically." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45274.
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Oil seals in centrifugal compressors reduce leakage of the process gas into the support bearings and ambient. Under certain operating conditions of speed and pressure, oil seals lock, becoming a source of hydrodynamic instability due to excessively large cross coupled stiffness coefficients. It is a common practice to machine circumferential grooves, breaking the seal land, to isolate shear flow induced film pressures in contiguous lands, and hence reducing the seal cross coupled stiffnesses. Published tests results for oil seal rings shows that an inner land groove, shallow or deep, does not actually reduce the cross-stiffnesses as much as conventional models predict. In addition, the tested grooved oil seals evidenced large added mass coefficients; while predictive models, based on classical lubrication theory, neglect fluid inertia effects. This paper introduces a bulk-flow model for groove oil seals operating eccentrically and its solution via the finite element method. The analysis relies on an effective groove depth, different from the physical depth, which delimits the upper boundary for the squeeze film flow. Predictions of rotordynamic force coefficients are compared to published experimental force coefficients for a smooth land seal and a seal with a single inner groove with depth equaling 15 times the land clearance. The test data represent operation at 10 krpm and 70 bar supply pressure, and four journal eccentricity ratios (e/c = 0, 0.3, 0.5, 0.7). Predictions from the current model agree with the test data for operation at the lowest eccentricities (e/c = 0.3); discrepancies increasing at larger journal eccentricities. The new flow model is a significant improvement towards the accurate estimation of grooved seal cross-coupled stiffnesses and added mass coefficients; the later previously ignored or largely under predicted.