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Journal articles on the topic 'Eppler'

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Published: 4 June 2021

Last updated: 27 January 2023

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Aguilar, Jonathan, Laura Isabel Velásquez, Ainhoa Rubio Clemente, and Edwin Chica. "Numerical analysis on the use of multi-element blades in a horizontal-axis hydrokinetic turbine." Journal of Mechanical Engineering and Sciences 14, no. 4 (2020): 7328–47. http://dx.doi.org/10.15282/jmes.14.4.2020.02.0576.

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The blades of a hydrokinetic turbine have a great impact on its performance due to they are the elements responsible for capturing the kinetic energy from water and transform it into rotational mechanical energy. In this work, numerical analyses on the performance of a multi-element blade section were developed. The lift and drag coefficients (CL and CD, respectively) of the hydrofoils with traditional and multi-element configurations were studied. For this purpose, 2D numerical analyses were conducted by using JavaFoil code. S805, S822, Eppler 420, Eppler 421, Eppler 422, Eppler 423, Eppler 857, Wortmann FX 74-CL5-140, Wortmann FX 74-CL5-140 MOD, Douglas/Liebeck LA203A, Selig S1210, Selig S1223 and UI-1720 profiles were tested. The results indicated that the Eppler 420 multi-element hydrofoil provided high efficiency to the turbine. This was attributed to its higher relationship between the maximum CL and CD (CLmax /CD), which was equal to 47.77, compared to that of the Selig S1223 profile (39.59) and other hydrofoils studied. Therefore, the final optimized blade section selected was an Eppler 420 multi-element hydrofoil with a flap chord length of 70% of that of the main profile. The hydrodynamic and structural designs of the optimized blade section were validated with detailed 3D numerical models, through ANSYs Fluent software. The fluid and structural domains were connected using one-way coupling. The influence of the blade geometry and the operational parameters on the stresses supported by the blades were found by analyzing the fluid-structure interaction. From the numerical analyses conducted, it was observed that the blades did not exhibit structural fails. In this regard, the multi-element hydrofoil might be used for the design of a horizontal-axis hydrokinetic turbine with a high efficiency.

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Siddiqi, Z., and JW Lee. "A computational fluid dynamics investigation of subsonic wing designs for unmanned aerial vehicle application." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 15 (2019): 5543–52. http://dx.doi.org/10.1177/0954410019852553.

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The wing of an unmanned aerial vehicle, RQ-7 Shadow, is modified to study the changes in the aerodynamics of the wing. The main focus is to investigate the effects of changing the components of wing design when the aircraft climbs and accelerates. These component modifications included changing the airfoil, planform, aspect ratio, and adding a winglet. Another objective is to study the efficacy of employing high-lift airfoils like the EPPLER 559 for subsonic unmanned aerial vehicle applications. For this, five wing designs are considered in this paper. Computational fluid dynamics simulations using ANSYS FLUENT® are conducted for each wing design. The C L /C D ratios for all the wings are calculated at increasing angles of attack (simulating Climbing) and increasing speed (simulating Acceleration). Compared to the NACA 4415 airfoil, which is utilized by the RQ-7 Shadow, the EPPLER 559 provides an increase in lift at the low angles of attack, but yields less of these benefits as the angle of attack increases. The tapered planform significantly reduces the high drag associated with the EPPLER 559 airfoil. The generation of higher lift forces with lower drag is further achieved by increasing the aspect ratio and through the addition of a winglet. When compared to the NACA 4415 airfoil, it is concluded that the EPPLER 559 airfoil is a viable candidate for subsonic unmanned aerial vehicle applications only when the components of wing design are altered. The performance of the wings that employ the EPPLER 559 airfoil improves when the planform is changed from rectangular to tapered, when the aspect ratio is increased and when a winglet is added.

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Cheng, H. K. "Airfoil Design and Data (Richard Eppler)." SIAM Review 34, no. 2 (1992): 331–33. http://dx.doi.org/10.1137/1034070.

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Yass, Muhammad A. R., Saadi Turied Kurdi, and Mahmood Abdulzahra Shkara. "Integration of Optimum Power for Wind Turbine Blade at Different Cross Section." Journal of University of Babylon for Engineering Sciences 26, no. 7 (2018): 124–49. http://dx.doi.org/10.29196/jubes.v26i7.1498.

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This research analysis and optimizes the main wind horizontal turbine blade parameters for high-performance altitude with variable pitch blade angle for different blade cross-section unsymmetrical airfoil NACA 4412 and unsymmetrical airfoil supercritical Eppler 417. For deep specification, some wind horizontal turbine parameters kept constant through the proses method to integrate the highest behavior of windmill turbine power coefficient. The procedure analysis with FORTRAN.90 code ,then compare with German code and then optimized using Schmitz and Betz method for blade chord and lift to drag for blade pitch angle. From theoretical results discussion, important conclusions figured; also a recommendation for further work was suggested. Best optimization methods were Schmitz chord optimization and Lift/Drag twist optimization which increases the Cp 10.3% for Eppler 4417 and 9.5% for NACA 4412.All results were tabulated and plotted for all optimization results

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Liebeck, R. H. "Book Reviews: Airfoil Design and Data- Richard Eppler." AIAA Journal 31, no. 1 (1993): 217. http://dx.doi.org/10.2514/3.49012.

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Setyo Hariyadi, S. P., Sutardi, Wawan Aries Widodo, Muhammad Anis Mustaghfirin, and Arifandi Rachmadiyan. "Numerical study of flow characteristics on wing airfoil eppler 562 with whitcomb winglet variations." MATEC Web of Conferences 204 (2018): 04009. http://dx.doi.org/10.1051/matecconf/201820404009.

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Winglet is a tool used to improve the efficiency of aircraft and UAV performance by preventing fluid flow jump from lower surface to upper surface at wingtip. The addition of this winglet resulted in improved lift and reduction of drag force from the aircraft wing or UAV. From Whitcomb's research, it was found that the use of winglet on a full size airplane can increase fuel efficiency by 7%. The research led to the idea of conducting research on fluid flow characteristics on the UAV wing with the Eppler 562 airfoil combined with the whitcomb winglet. This numerical study was conducted using the Computational Fluid Dynamics (CFD) method based on the advantages of using this simulation that can review the fluid flow in macroscopic way. This study is provide accurate fluid flow visualization results and can improve the performance of the wings when compared with wings without winglet (plain wing). Wing with the Eppler 562 airfoil combined with the whitcomb winglet results reduction in rotating motion that makes velocity components as opposed to lift.

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A. R. Yass, Muhammad, Raghad Majeed Rasheed, and Amer Hamad Muhiesen. "Contribution of lift-to-drag ratio on power coefficient of HAWT blade for different cross-sections." Open Engineering 12, no. 1 (2022): 716–28. http://dx.doi.org/10.1515/eng-2022-0324.

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Abstract The aim of this study is to integrate the best lift-to-drag ratio zone to chief the highest power coefficient for horizontal axis wind turbine (HAWT) blade. Different cross-section, symmetrical, unsymmetrical, and supercritical airfoils (NACA 0012, NACA 4412, and Eppler 417) are used. FORTRAN code (f.90) was built to calculate aerodynamic data and the power coefficient based on Blade Element Momentum theory. This article deals selection of the most effective zone from the lift-to-drag ratio versus blade radius curve that gives the best incidence angle distribution. The results show a good performance that leads to approximated equal lift-to-drag distribution along the blade radius that indicates the highest power coefficient of at least 15% increases. The highest values of the power coefficient of NACA 0012, NACA 4412, and Eppler 417 were 0.476, 0.4966, and 0.482, respectively. The lift-to-drag ratio distribution zones were the most specific method of generating the maximum power coefficient for the HAWT blade. Important results and conclusion were found for further blade design.

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Maklakov, D. V., and A. N. Uglov. "On the maximum drag of a curved plate in flow with a wake." European Journal of Applied Mathematics 6, no. 5 (1995): 517–27. http://dx.doi.org/10.1017/s0956792500002011.

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In this work exact upper bounds of the drag force are found for curved plates of fixed total arc-length in flow with a wake, which forms according to the Joukowsky-Roshko-Eppler model. The shapes of maximum drag are determined in an explicit analytical form and can be interpreted as those of ideal parachutes.

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Amromin, E. L. "Scale Effect of Cavitation Inception on a 2D Eppler Hydrofoil." Journal of Fluids Engineering 124, no. 1 (2001): 186–93. http://dx.doi.org/10.1115/1.1427689.

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Cavitation inception on an E817 hydrofoil issued from an inverse calculus for ideal fluid has been numerically analyzed for speeds and scales inherent to both model test and full-scale marine conditions. The computations have been carried out with account to the Reynolds number effect on hydrofoil lift and combined effect of the Reynolds number and Weber number on the equilibrium of sheet cavities in the hydrofoil boundary layer. Different levels of scale effects for cavitation inception on suction and pressure sides of E817 hydrofoil are shown. Comparison with the scale effect of cavitation inception on conventional NACA-0012 hydrofoil has helped to explain this difference. Issues in blade design with sections similar to E817 are discussed.

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Vaziri, Nima, Ming-Jyh Chern, and Tzyy-Leng Horng. "Simulation of dynamic stall using direct-forcing immersed boundary method at low Reynolds number." Aircraft Engineering and Aerospace Technology 90, no. 5 (2018): 869–76. http://dx.doi.org/10.1108/aeat-05-2017-0128.

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Purpose The purpose of this study is simulation of dynamic stall behavior around the Eppler 387 airfoil in the low Reynolds number flow with a direct-forcing immersed boundary (DFIB) numerical model. Design/methodology/approach A ray-casting method is used to define the airfoil geometry. The governing continuity and Navier–Stokes momentum equations and boundary conditions are solved using the DFIB method. Findings The purposed method is validated against numerical results from alternative schemes and experimental data on static and oscillating airfoil. A base flow regime and different vortices patterns are observed, in accordance with other previously published investigations. Also, the effects of the reduced frequency, the pitch oscillation amplitude and the Reynolds number are studied. The results show that the reduced frequency has a major effect on the flow field and the force coefficients of the airfoil. On the other hand, the Reynolds number of the flow has a little effect on the dynamic stall characteristics of the airfoil at least in the laminar range. Practical implications It is demonstrated that the DFIB model provides an accurate representation of dynamic stall phenomenon. Originality/value The results show that the dynamic stall behavior around the Eppler 387 is different than the general dynamic stall behavior understanding in the shedding phase.

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Chandra, Sushil, and Rajan Tyagi. "Study of Eppler 423 Airfoil with Gurney Flap and Vortex Generators." Advances in Aerospace Science and Technology 05, no. 01 (2020): 1–19. http://dx.doi.org/10.4236/aast.2020.51001.

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Diego, Betancur, Ardila Gonzalo, and Chica Lenin. "Design and hydrodynamic analysis of horizontal-axis hydrokinetic turbines with three different hydrofoils by CFD." Journal of Applied Engineering Science 18, no. 4 (2020): 529–36. http://dx.doi.org/10.5937/jaes0-25273.

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The conversion of kinetic energy that comes from low-head water currents to electrical energy has gained importance in recent years due to its low environmental and social impact. Horizontal axis hydrokinetic turbines are one of the most used devices for the conversion of this type of energy [1], being an emerging technology more studies are required to improve the understanding and functioning of these devices. In this context, the hydrodynamic study to obtain the characteristic curves of the turbines are fundamental. This article presents the design and hydrodynamic analysis for three horizontal axis tri-blade hydrokinetic turbine rotors with commercial profiles (NACA 4412, EPPLER E817 and NRELS802). The Blade Element Momentum (BEM) was used to design three rotors. The DesignModeler, Meshing and CFX modules from the ANSYS® commercial package were used to discretize the control volumes and configure the numerical study. In addition, Grid Convergence Index (GCI) analysis was performed to evaluate the precision of the results. The computational fluid dynamics (CFD) was used to observe the behavior of the fluid by varying the speed of rotation of the turbines from 0.1 rad s-1 to 40 rad s-1, obtaining power coefficient of 0.390 to 0.435. For a maximum shaft power of 105W. In addition, it is evident that for the same conditions the rotor designed with the EPPLER E817 profile presents better performance than built with the NACA4412 and NREL S802.

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Astolfi, J. A., P. Dorange, J. Y. Billard, and I. Cid Tomas. "An Experimental Investigation of Cavitation Inception and Development on a Two-Dimensional Eppler Hydrofoil." Journal of Fluids Engineering 122, no. 1 (1999): 164–73. http://dx.doi.org/10.1115/1.483239.

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Cavitation inception and development on a two-dimensional foil with an Eppler E817 cross section issued from an inverse calculus have been experimentally investigated. The foil is theoretically designed to have a wide cavitation-free bucket allowing a large range of cavitation-free angle of incidence (Eppler, R., 1990, Airfoil Design and Data, Springer-Verlag, Berlin). The inception cavitation numbers, the noise level, the velocity distribution, the minimum pressure coefficient, the cavitation patterns (bubble, leading edge “band type” cavitation, attached sheet cavity), together with the sheet cavity length have been experimentally determined. Effects on the velocity field have been studied too with a slightly developed cavitation. For angles of incidence larger than 1 deg, a great difference exists between the inception cavitation number and the theoretical minimum pressure coefficient. However it is in agreement with the measured one obtained from velocity measurements (for 0 deg<α<6 deg). Discrepancy between theory and experiment on scale models is generally attributed to a flow separation at the leading edge. Although there are some indications of a separated flow at the leading edge, the velocity measurements do not show reverse flow with clearly detected negative velocities excepted for a large angle of incidence equal to 10 deg. Concerning sheet cavity development, the length cavity is found to scale as [σ/2α−αiσ]−m with m close to 2, for length cavities that do not exceed half the foil chord and for σ/2α−αiσ larger than about 30. [S0098-2202(00)00201-7]

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Fodi, Rodrigo Pellegrini, Lucas Leandro Simmermam, and Luciano de Souza Ribeiro Bueno. "Determinação da sustentação gerada pelo aerofólio EPPLER-423 através de método numérico-teórico e experimental." Brazilian Journal of Development 8, no. 11 (2022): 72440–45. http://dx.doi.org/10.34117/bjdv8n11-110.

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O estudo dos fluidos é sustentado por um compromisso entre teoria e experimentação. No entanto, o uso de simplificações, eventualmente, distancia os resultados teóricos da realidade. Tais discordâncias, podem ser reduzidas mediante execução de ensaios experimentais, ou CFD. Este estudo tem como objetivo, determinar a força de sustentação do perfil alar Eppler – 423, para pequenos ângulos de ataque em diferentes velocidades de escoamento, através de experimento prático e método numérico-teórico. Os principais resultados da pesquisa demonstram que o modelo numérico-teórico alcançou valores próximos dos experimentais para o ângulo de 10°. Simultaneamente, para baixas velocidades, as demais inclinações testadas ressaltaram uma boa concordância entre os dois métodos abordados.

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Souza, Ramon Jorge de, Reuben Bezerra Barbosa, Augusto Cézar de Aquino Cabral, and Sandra Maria dos Santos. "Avaliação da Qualidade das Informações disponibilizadas no Portal da Transparência do Estado do Ceará." Encontros Bibli: revista eletrônica de biblioteconomia e ciência da informação 24, no. 54 (2019): 91–104. http://dx.doi.org/10.5007/1518-2924.2019v24n54p91.

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O objetivo deste artigo é analisar a qualidade das informações disponibilizadas no Portal da Transparência do Estado do Ceará. Para tanto, foi realizada uma pesquisa quantitativa e descritiva, com base em um levantamento com os analistas, técnicos e auxiliares de controle externo do Tribunal de Contas do Estado do Ceará para avaliar a percepção destes acerca das quatro dimensões e dezesseis atributos de qualidade definidos no modelo de avaliação de Eppler (2006). Os resultados demonstram que o Portal da Transparência apresenta informações de alta relevância e alta adequação. Conclui-se que o Portal da Transparência destaca-se quanto ao atendimento dos atributos relacionados à clareza, aplicabilidade, correção, atualidade, oportunidade e velocidade e apresenta falhas quanto ao atributo de rastreabilidade.

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Suranto Putro, Setyo Hariyadi, Sutardi Sutardi, Wawan Aries Widodo, and Bambang Juni Pitoyo. "Comparative Study Aerodynamics Effects of Wingtip Fence Winglet on Fix Wing Airfoil Eppler E562." WARTA ARDHIA 45, no. 2 (2021): 67. http://dx.doi.org/10.25104/wa.v45i2.356.67-76.

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Wings on airplanes and Unmanned Aerial Vehicles (UAVs) have a very important role in the formation of lift forces. This is because most of the lifting force arises on the wing. Therefore, aircraft designers pay great attention to wing modification. Today's aircraft designers tend to provide geometric modifications displayed in computational applications so that visualization of fluid flow can appear clearly. By increasing the lift as high as possible on the wing and lowering the drag as low as possible, it is expected that high aerodynamic efficiency will be achieved in air transportation. This research was done numerically by using the turbulence model k-ω SST. Reynolds number in this research was 2,34 x 104 with the angle of attacks are 0o, 2o, 4o, 6o, 8o, 10o, 12o, 15o, 17o and 19o. The model specimen is wing airfoil Eppler 562 with winglets. Two types of wingtips are used: forward and rearward wingtip fence. From this study, it was found that the wingtip fence reduced the strength of vorticity magnitude on the x-axis and z-axis compared to plain wings. With the addition of a wingtip fence, it has a significant effect on the shape of the vorticity magnitude behind the wing. This indicates a decrease in induced drag on the wing which has a wingtip fence.

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REDCAY, ANNA. "Dependent States: The Child's Part in Nineteenth-Century American Culture by Karen Sánchez-Eppler." Critical Quarterly 51, no. 1 (2009): 139–46. http://dx.doi.org/10.1111/j.1467-8705.2009.01841.x.

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Elimelech, Y., R. Arieli, and G. Iosilevskii. "Flow over NACA-0009 and Eppler-61 Airfoils at Reynolds Numbers 5000 and 60,000." AIAA Journal 45, no. 10 (2007): 2414–21. http://dx.doi.org/10.2514/1.22376.

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Jackson, Kathy Merlock. "Dependent States: The Child's Part in Nineteenth-Century American Culture by Karen Sánchez-Eppler." Journal of American Culture 30, no. 1 (2007): 122–23. http://dx.doi.org/10.1111/j.1542-734x.2007.00479.x.

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Levin, Matthew. "Sarah Eppler Janda. Prairie Power: Student Activism, Counterculture, and Backlash in Oklahoma, 1962–1972." American Historical Review 124, no. 2 (2019): 707–8. http://dx.doi.org/10.1093/ahr/rhz136.

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Samuthira Pandi, Jawahar Sivabharathy, and Sanjay Mittal. "Wake transitions and laminar separation bubble in the flow past an Eppler 61 airfoil." Physics of Fluids 31, no. 11 (2019): 114102. http://dx.doi.org/10.1063/1.5113823.

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Sa, Jeong Hwan, Soo Hyung Park, Chang Joo Kim, and Jung Keun Park. "Low-Reynolds number flow computation for eppler 387 wing using hybrid DES/transition model." Journal of Mechanical Science and Technology 29, no. 5 (2015): 1837–47. http://dx.doi.org/10.1007/s12206-015-0404-7.

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Ajalli, Fariba, Mahmoud Mani, and Mozhgan Gharakhanlou. "Wake Frequency Analysis of a Plunging Airfoil with Trailing-Edge Strips." Applied Mechanics and Materials 225 (November 2012): 3–7. http://dx.doi.org/10.4028/www.scientific.net/amm.225.3.

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Experimental measurements were conducted on a plunging Eppler 361 strip flapped airfoil to study wake structure in the wake. The heights of strip flap were 2.6% and 3.3% chord. The velocity in the wake was measured by hot-wire anemometry. It was found that the trailing-edge strip had different effects on the plunging wake profile during the oscillation cycle. At initial angle of 0 degree, the trailing-edge strip causes more velocity defect in the oscillation phases of 180º and 270º. At high initial angle 12 degrees, a significant decrease in value of velocity is found at 180º because of the leading edge vortex shedding. The power spectra of dominant frequencies were significantly increased by fitting the strip flap on the plunging airfoil.

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R., Anushka, Diksha Chaudary, Ravi Ranjan Singh, Satish Wadel S, P. A. Aswatha Narayana, and Ashish Kumar Gupta. "Numerical simulation of flow over EPPLER 387 at low Reynolds number and comparison with experiment." International Journal of Scientific and Research Publications (IJSRP) 9, no. 1 (2019): p8528. http://dx.doi.org/10.29322/ijsrp.9.01.2019.p8528.

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Hariyadi, Setyo, Sutardi Sutardi, Wawan Aries Widodo, and Bambang Juni Pitoyo. "Comparative Study of Forward Wingtip Fence and Rearward Wingtip Fence on Wing Airfoil Eppler E562." Journal of Energy, Mechanical, Material, and Manufacturing Engineering 5, no. 1 (2020): 25. http://dx.doi.org/10.22219/jemmme.v5i1.11968.

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The perfect wing is a dream that many airplanes has manufactured have been striving to achieve since the beginning of the airplane design. There are some aspect that most influence in aircraft design lift, drag, thrust, and weight. The combination of these aspects leads to a decrease in fuel consumption, which reduces pollution in our atmosphere and increase in economic revenue. One way to improve aircraft performance is to modify the tip of the wing geometry, which has become a common sight on today’s airplanes. With computational programs, the effects on drag due to wingtip devices can be previewed. This research was done numerically by using turbulence model k-ω SST. Reynolds number in this research was 2,34 x 10 4 with angle of attacks are 0o, 2o, 4o, 6o, 8o, 10o, 12o, 15o, 17o and 19o. The model specimen is wing airfoil Eppler 562 with winglets. Two types of wingtips are used: forward and rearward wingtip fence. From this study, it was found that wingtip fence reduced the strength of vorticity magnitude on the x axis compared to plain wings. The leakage of fluid flow effect at the leading edge corner of the wingtip, giving pressure gradient and slightly shifting towards the trailing edge. this occurs in the plain wing and rearward wingtip fence but does not occur in the forward wingtip fence..

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Smith, Sherry L. "Prairie Power: Student Activism, Counterculture, and Backlash in Oklahoma, 1962–1972 by Sarah Eppler Janda." Great Plains Quarterly 39, no. 2 (2019): 220–21. http://dx.doi.org/10.1353/gpq.2019.0033.

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Burroughs, Chelsea. "Prairie Power: Student Activism, Counterculture, and Backlash in Oklahoma 1962–1972. By Sarah Eppler Janda." Western Historical Quarterly 50, no. 2 (2019): 167–68. http://dx.doi.org/10.1093/whq/whz005.

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Cohen, Robert. "Prairie Power: Student Activism, Counterculture, and Backlash in Oklahoma, 1962-1972 by Sarah Eppler Janda." Journal of Southern History 85, no. 1 (2019): 222–23. http://dx.doi.org/10.1353/soh.2019.0065.

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Yang, S. L., Y. L. Chang, and O. Arici. "Incompressible Navier-Stokes Computation of the NREL Airfoils Using a Symmetric Total Variational Diminishing Scheme." Journal of Solar Energy Engineering 116, no. 4 (1994): 174–82. http://dx.doi.org/10.1115/1.2930079.

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The purpose of this paper is to present a numerical study of flow fields for the NREL S805 and S809 airfoils using a spatially second-order symmetric total variational diminishing scheme. The steady two-dimensional flow is modeled as turbulent, viscous, and incompressible and is formulated in the pseudo-compressible form. The turbulent flow is closed by the Baldwin-Lomax algebraic turbulence model. Numerical solutions are obtained by the implicit approximate-factorization method. The accuracy of the numerical results is compared with the Delft two-dimensional wind tunnel test data. For comparison, the Eppler code results are also included. Numerical solutions of pressure and lift coefficients show good agreement with the experimental data, but not the drag coefficients. To properly simulate the post-stall flow field, a better turbulence model should be used.

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Lasauskas, Eduardas, and Laurynas Naujokaiti. "ANALYSIS OF THREE WING SECTIONS." Aviation 13, no. 1 (2009): 3–10. http://dx.doi.org/10.3846/1648-7788.2009.13.3-10.

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Three wing sections FX66-S-196VI, E603 and AH82–150A were analyzed. Measured data of these wing sections are published. First wing section was measured in Stuttgart University and in Delft University of Technology, when other two wing sections were measured in Stuttgart University. These wing sections have different behavior in the region of maximum lift. FX66‐S‐196VI wing section has sharp drop in lift. The stall of the second and third wing sections is smooth, though different. All wing sections are affected by laminar separation bubbles. The calculations were performed using three codes: Eppler Program System, XFOIL and RFOIL. Eppler's code uses non‐interacted inviscid plus boundary layer method. Influence of separation is estimated using empirical correction in this method. XFOIL code of Mark Drela, MIT uses interacted zonal viscous/inviscid method. The wall transpiration model in this code approximates the displacement effect on the outer inviscid flow. RFOIL is a modification of XFOIL code for application in wind turbines performed at Delft University of Technology. The code's prediction of the airfoil performance around the two dimensional maximum lift was enhanced. The comparison of calculated and measured data is presented and analyzed. Santrauka Tyrimuose analizuotos profiliu FX 66-S-196 V1, E603 ir AH82–150A charakteristiku teorines reikšmes, apskaičiuotos XFOIL, RFOIL ir PROFIL05 programomis. Gautos teorines reikšmes palygintos su jau atliktu eksperimentiniu tyrinejimu rezultatais. Pirmas profilis buvo tyrinejamas Delft technologijos universitete (Olandija) ir Štutgarto universitete (Vokietija), like du ‐ Štutgarto universitete. Visi profiliai turi skirtingas maksimalios keliamosios jegos dalis. Profilio FX 66‐S‐196 V1 keliamoji jega mažeja staiga. Kitu profiliu keliamoji jega kinta tolygiai, tačiau skirtingai. Visu profiliu ucharakteristikas itakoja laminarinis atsiskyrimo burbulas.

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Jang, H. M., J. A. Ekaterinaris, M. F. Platzer, and T. Cebeci. "Essential Ingredients for the Computation of Steady and Unsteady Blade Boundary Layers." Journal of Turbomachinery 113, no. 4 (1991): 608–16. http://dx.doi.org/10.1115/1.2929124.

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Two methods are described for calculating pressure distributions and boundary layers on blades subjected to low Reynolds numbers and ramp-type motion. The first is based on an interactive scheme in which the inviscid flow is computed by a panel method and the boundary layer flow by an inverse method that makes use of the Hilbert integral to couple the solutions of the inviscid and viscous flow equations. The second method is based on the solution of the compressible Navier–Stokes equations with an embedded grid technique that permits accurate calculation of boundary layer flows. Studies for the Eppler-387 and NACA-0012 airfoils indicate that both methods can be used to calculate the behavior of unsteady blade boundary layers at low Reynolds numbers provided that the location of transition is computed with the en method and the transitional region is modeled properly.

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Arifin, Zainal, Suyitno Suyitno, Dominicus Danardono Dwi Prija Tjahjana, et al. "Aerodynamic Characteristics of Ahmed Body with Inverted Airfoil Eppler 423 and Gurney Flap on Fastback Car." Automotive Experiences 5, no. 3 (2022): 355–70. http://dx.doi.org/10.31603/ae.7067.

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The installation of aerodynamic devices, such as rear wings with the application of a Gurney flap, is very important to improve the performance of vehicles and can generate downforce and reduce slip when a car turns and brakes. The goal of this study was to determine the aerodynamic characteristics of the addition of a rear wing using an Eppler 423 airfoil, which was applied with a Gurney flap featuring variations in the angle of attack and the height of the Gurney flap. The rear wing was mounted on the Ahmed body with a rear slant angle of 15°, which is similar to the configuration on a fastback type car. This research was conducted by 3D modeling through computational fluid dynamics (CFD) simulation using ANSYS Student R18.2 by using ahmed body design. There are three variations in the angle of attack for the rear wing (0°, 7.5°, and 15°), as well as five variations in Gurney flap height of 0%, 0.5%, 1%, 1.5%, and 2% for the chord-line length. In this study, the best variation was found at an angle of attack of 15⁰ with a height of 2% C. From this configuration improved CL/CD ratio by 25.36% when compared to the results without a Gurney flap.

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Paranjape, Aniruddha Deepak, Anhad Singh Bajaj, Shaheen Thimmaiah Palanganda, Radha Parikh, Raahil Nayak, and Jayakrishnan Radhakrishnan. "Computational analysis of high-lift-generating airfoils for diffuser-augmented wind turbines." Wind Energy Science 6, no. 1 (2021): 149–57. http://dx.doi.org/10.5194/wes-6-149-2021.

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Abstract. The impetus towards sustainable energy production and energy access has led to considerable research and development on decentralized generators, in particular diffuser-augmented wind turbines. This paper aims to characterize the performance of diffuser-augmented wind turbines (DAWTs) using high-lift airfoils employing a three-step computational analysis. The study is based on computational fluid dynamics, and the analysis is carried out by solving the unsteady Reynolds-averaged Navier–Stokes (URANS) equations in two dimensions. The rotor blades are modeled as an actuator disk, across which a pressure drop is imposed analogous to a three-dimensional rotor. We study the change in performance of the enclosed turbine with varying diffuser cross-sectional geometry. In particular, this paper characterizes the effect of a flange on the flow augmentation provided by the diffuser. We conclude that at the end of the three-step analysis, Eppler 423 showed the maximum velocity augmentation.

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King, Helen. "‘Children My Age Should Be Reading Books Like Journey to Jo’burg’: Patterns of Anti-Racist Reading in Archived Reader Responses." International Research in Children's Literature 15, no. 3 (2022): 264–78. http://dx.doi.org/10.3366/ircl.2022.0466.

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Using archived reader responses to Beverley Naidoo’s Journey to Jo’burg (1985), I employ the framework of Antiracist Pedagogy to explore how readers engage with the novel’s indictment of racism in apartheid South Africa. Drawing on classroom responses from a variety of global contexts, I develop a context-orientated approach to reader response criticism that draws on theories of child agency developed by Karen Sánchez-Eppler (2005) and Robin Bernstein (2011). Using this approach, I identify four recurring patterns of engagement with the theme of racism: affect, identification, resistance, and critical literacy. Through my analysis, Naidoo’s child readers emerge as partial subjects whose agency is not fixed but continuously negotiated in the play between text and context. These readers claim authority to speak about literature and their own experiences of racism, and conceive of radical, anti-racist literature as essential in their lives and those of their fellow children.

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Siregar, Ansor Salim, Mulyadi Mulyadi, and Syaiful Arief. "Analisis Kegagalan Laminasi Komposit Epoksi/Serat Karbon Pada Sayap Pesawat Tanpa Awak." Piston: Journal of Technical Engineering 5, no. 2 (2022): 108. http://dx.doi.org/10.32493/pjte.v5i2.18596.

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This study aims to analyze the initial failure value using the Tsai – Wu criteria from the wing skin of an unmanned aircraft with the Eppler 214 airfoil model. The study was carried out using computer modeling with Abaqus software. The material used is an epoxy composite which is carbon fiber. The composites used in the wing skins have two different arrangement sequences, namely the fiber layer arrangement sequence 1 [00/900]8s and the layer sequence 2 [00/+450/-450/900]2s. The load given to the wing is a pressure of 0.40077 MPa. The results for the fiber layer sequence 1 [00/900]8s at the maximum stress distribution are 5.067 x 104 MPa and in the fiber layer sequence, 2 [00/+450/-450/900]2s the maximum value is 4.205 x 104 MPa. While the sequences consist of fiber layer 1 and layer 2 sequence layers, the Tsai – Wu failure meets the Tsai – Wu failure criteria because almost all of them fail

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S.P, Setyo Hariyadi, Bambang Junipitoyo, Sutardi ., and Wawan Aries Widodo. "Stall Behavior Curved Planform Wing Analysis with Low Reynolds Number on Aerodynamic Performances of Wing Airfoil Eppler 562." Journal of Mechanical Engineering 19, no. 1 (2022): 201–20. http://dx.doi.org/10.24191/jmeche.v19i1.19697.

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On airplanes and UAVs, a stall is something that is always attempted to avoid. Stalling can also be aided by the employment of planform wings with varying geometry. Curved wing variations are often used in UAV applications, especially at low Reynolds numbers. This study discusses stall behavior on rectangular, elliptical, semi-elliptical, and Schuemann wings. Numerical simulations were performed using the turbulent k-ω SST model using Ansys Fluent 19.1. The airfoil used in this study was Eppler 562 at Reynolds number 2.34 x 104 . The angles of attack observed were 0o , 2o , 4o , 6o , 8o , 10o ,12o , 15o , 17o , 19o , and 20o . The Schuemann wing has the best performance that is indicated by the delaying of the stall point, which is at an angle of attack α = 15o , while the rectangular wing produces the highest lift to drag ratio compared to other planform wings. The confluence of the main flow and backflow forms towards the mid-span as the angle of attack increases. The rectangular wing produces high vorticity in the wingtip area due to the tip- vortex phenomenon, while the elliptical and Schuemann wing in the leading edge area due to the geometry of the leading edge.

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Hariyadi, S., S. Sutardi, W. A. Widodo, B. J. Pitoyo, N. Pambudiyatno, and I. Sonhaji. "Numerical Analysis of the Reynolds Number Effect on the Aerodynamic Performance Wing Airfoil Eppler 562 with Wingtip Fence." Journal of Physics: Conference Series 1381 (November 2019): 012055. http://dx.doi.org/10.1088/1742-6596/1381/1/012055.

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Che Ibrahim, Che Intan Hartini, and Aslam Abdullah. "Flow Topology around Low Reynolds Number Airfoils with Vortex Shedding." CFD Letters 12, no. 12 (2020): 85–103. http://dx.doi.org/10.37934/cfdl.12.12.85103.

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In depth studies on the vortex formation process as well as the periodic behavior of the reattachment profile have been mainly sparked by broad discussions on the flow topology. While the topology methodology is quite well established, the majority of airfoil types have still not been covered. In this study, six low Reynolds number airfoils were considered to investigate the separation bubble structure, vortex shedding and reattachment point. This was done by means of computational fluid dynamics simulations involving the airflow passing several Eppler and Selig models. The method was validated against an established mathematical relationship to indicate that both simulations and analysis technique were reliable. It was observed that the phenomena under investigation directly affect the airfoils aerodynamic performance. In particular, vortex shedding and big reattachment length contribute to the minimum lift. Moreover, high number of vortices in the separation bubble as well as secondary separation bubble result in maximum drag. The results which correspond to low Reynolds number airfoils are applicable in micro aerial vehicles field.

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Hattab, Raphael Eppler, Ilan Meshoulam, and Israel Doron. "SUPPORTING AN OLDER WORKFORCE BY CREATING AGE-FRIENDLY WORKPLACES: INTRODUCING A NEW MULTIDIMENSIONAL MODEL." Innovation in Aging 3, Supplement_1 (2019): S193. http://dx.doi.org/10.1093/geroni/igz038.693.

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Abstract Creating age-friendly workplace environments is considered a central organizational approach for addressing the challenges of supporting an aging and older workforce. However, there are no concrete definitions or theoretical frameworks that explain the full meaning, assumptions and basic processes of this concept. This paper critically reviews the conceptualizations of the age-friendly workplace in the fields of organizational psychology and gerontology, and proposes (a) a new working definition of the concept, and (b) a multidimensional model that consists of a typology of age-friendly dimensions, representing the implications of human resource policies and practices that demonstrate the ways in which organizational climate and organizational culture support aging workers. This framework enables a better understanding of the organizational-occupational realities within an aging and older labor market, and thus serves as an effective foundation upon which future organizational measurements can be constructed. This presentation is based on the article: Eppler-Hattab, R., Meshoulam, I., & Doron, I. (2019). Conceptualizing Age-Friendliness in Workplaces: Proposing a New Multidimensional Model. The Gerontologist. 10.1093/geront/gny184.

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YEUNG, W. W. H., and G. V. PARKINSON. "Base pressure prediction in bluff-body potential-flow models." Journal of Fluid Mechanics 423 (November 3, 2000): 381–94. http://dx.doi.org/10.1017/s0022112000002044.

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In a recent study by Yeung & Parkinson (1997), a wake width was proposed which allowed the bluff-body potential-flow model by Parkinson & Jandali (1970) to be extended to include the flow around an oblique flat plate. By incorporating this wake width in the momentum equation originally derived by Eppler (1954) for separated flow, the drag of the plate is related to its inclination and base pressure through a simple analytical condition. It allows the base pressure, which is usually treated as an empirical input, to be determined theoretically and thus the model becomes self-contained. Predictions of the base pressure, drag and width of wake are found to be in reasonable agreement with the experimental data. When applied to the symmetrical flow around a wedge of arbitrary vertex angle, similar agreement with experimental measurements is obtained as well. It is also demonstrated that this condition is compatible with the free-streamline models by Wu (1962) and Wu & Wang (1964) such that the corresponding predictions are in good agreement with experiment.

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Bardera, Rafael, Ángel A. Rodríguez-Sevillano, and Estela Barroso. "Numerical and Experimental Study of Aerodynamic Performances of a Morphing Micro Air Vehicle." Applied Mechanics 2, no. 3 (2021): 442–61. http://dx.doi.org/10.3390/applmech2030025.

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The present work is focused on the investigation of the aerodynamic performances of a novedous bioinspired morphing Micro Air Vehicle (MAV) with an adaptive wing structure geometry. For this purpose, a numerical study of Computational Fluid Dynamics (CFD) implemented by Ansys Fluent 15.0 was performed in order to obtain insight about the aerodynamic effect of wing structure deformation when morphing devices are used, and its influence on the global aerodynamic parameters related with aircraft performances. On the other hand, an experimental study using the Particle Image Velocimetry technique and balance measurements in a Low-Speed Wind Tunnel was conducted to obtain experimental information about performances measured to establish a comparison between both, experimental and numerical results. The Micro Air Vehicle (MAV) presents a Zimmerman wing with an Eppler 61 airfoil. Three different wing configurations according to curvature and thickness variations and for all angles of attack have been studied. A comparative analysis based on aerodynamic features is performed by an assessment of lift coefficient (CL), total aerodynamic drag coefficient (CD) and aerodynamic efficiency as lift/drag ratio (CL/CD) in order to conclude the best wing configuration in terms of aerodynamic performance.

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Yang, S. L., Y. L. Chang та O. Arici. "Navier-Stokes Computations of the NREL Airfoil Using a κ — ω Turbulent Model at High Angles of Attack". Journal of Solar Energy Engineering 117, № 4 (1995): 304–10. http://dx.doi.org/10.1115/1.2847864.

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This paper presents a two-dimensional numerical simulation of the turbulent flow fields for the NREL (National Renewable Energy Laboratory) S809 airfoil. The flow is modeled as steady, viscous, turbulent, and incompressible. The pseudo-compressible formulation is used for the time-averaged Navier-Stokes equations so that a time marching scheme developed for the compressible flow can be applied directly. The turbulent flow is simulated using Wilcox’s modified κ — ω model to account for the low Reynolds number effects near a solid wall and the model’s sensitivity to the freestream conditions. The governing equations are solved by an implicit approximate-factorization scheme. To correctly model the convection terms in the mean-flow and turbulence model equations, the symmetric TVD (Total Variational Diminishing) scheme is incorporated. The methodology developed is then applied to analyze the NREL S809 airfoil at various angles of attack (α) from 1 to 45 degrees. The accuracy of the numerical results is compared with the available Delft wind tunnel test data. For comparison, two Eppler code results at low angles of attack are also included. Depending on the value of α, preliminary results show excellent to fairly good agreement with the experimental data. Directions for future work are also discussed.

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Di Luca, Matteo, Stefano Mintchev, Yunxing Su, Eric Shaw, and Kenneth Breuer. "A bioinspired Separated Flow wing provides turbulence resilience and aerodynamic efficiency for miniature drones." Science Robotics 5, no. 38 (2020): eaay8533. http://dx.doi.org/10.1126/scirobotics.aay8533.

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Small-scale drones have enough sensing and computing power to find use across a growing number of applications. However, flying in the low–Reynolds number regime remains challenging. High sensitivity to atmospheric turbulence compromises vehicle stability and control, and low aerodynamic efficiency limits flight duration. Conventional wing designs have thus far failed to address these two deficiencies simultaneously. Here, we draw inspiration from nature’s small flyers to design a wing with lift generation robust to gusts and freestream turbulence without sacrificing aerodynamic efficiency. This performance is achieved by forcing flow separation at the airfoil leading edge. Water and wind tunnel measurements are used to demonstrate the working principle and aerodynamic performance of the wing, showing a substantial reduction in the sensitivity of lift force production to freestream turbulence, as compared with the performance of an Eppler E423 low–Reynolds number wing. The minimum cruise power of a custom-built 104-gram fixed-wing drone equipped with the Separated Flow wing was measured in the wind tunnel indicating an upper limit for the flight time of 170 minutes, which is about four times higher than comparable existing fixed-wing drones. In addition, we present scaling guidelines and outline future design and manufacturing challenges.

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Alekseev, Evgeny P. "”Not a Monotonous Artist”: Graphic Works by L. A. Epple Based on D. N. Mamin-Sibiryak’s Works." Izvestia of the Ural federal university. Series 2. Humanities and Arts 24, no. 4 (2022): 71–88. http://dx.doi.org/10.15826/izv2.2022.24.4.065.

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This article analyses the graphic cycle of L. A. Epple created based on D. N. Mamin-Sibiryak’s works in 1946–1952. Among the artist’s works, there are both illustrations for the collection For Children (1947) and easel compositions commissioned by the writer’s memorial museum in Sverdlovsk. A professional graphic artist, Epple worked thoughtfully and consistently with the works of the writer for many years, achieving expressiveness of images and artistic accuracy. The artist’s special position (a labour soldier in Sevurallag in 1941–1945, then a special settler in Sosva and Irbit in 1946–1952) led to the fact that his creative activity during these years was unknown to specialists. The artist’s name was not mentioned in the data of the collection of Mamin-Sibiryak’s works, and his easel paintings (kept in the collection of the United Museum of Writers of the Urals) were not published. In the late nineteenth — first half of the twentieth centuries, Mamin-Sibiryak’s works were illustrated and decorated by many Ural artists (S. I. Yakovlev, A. V. Kikin, Yu. A. Ivanov, A. A. Zhukov, N. P. Golubchikov, A. A. Kudrin, E. V. Gileva, etc.), but unlike L. A. Epple, the appeal to the literary heritage of the writer was for them only a brief episode of creative activity. Epple’s art project developed within the framework of an official order, hence the stylistics convenient for the mass reader, and a set of visual images was thought out. The principle of narrative fits into the aesthetics of book illustration of the 1940s–1950s, but in Epple’s graphic compositions, there is a feeling of intimacy, softness, some idealisation, and smoothness of images. Following the traditions of his teacher D. N. Kardovsky, Epple strives for the exact choice of the scene, the expressiveness of the entire composition and each character, the elaboration of details, and tries to reveal the psychology of the main characters. Choosing a realistic manner of performance, the artist proceeds from the nature of Mamin-Sibiryak’s oeuvre, with his thoroughness and journalistic narrative, respectful attitude to historical, ethnographic, and everyday realities.

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Faison, Elyssa. "Queer Diasporas. Edited by Cindy Patton and Benigno Sanchez-Eppler. Durham, N.C.: Duke University Press, 2000. 306 pp. $54.95 (cloth); $18.95 (paper)." Journal of Asian Studies 60, no. 3 (2001): 827–29. http://dx.doi.org/10.2307/2700117.

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Kisat, Courtney. "This Land Is Herland: Gendered Activism in Oklahoma from the 1870s to the 2010s ed. by Sarah Eppler Janda and Patricia Loughlin." Journal of Southern History 88, no. 3 (2022): 600–601. http://dx.doi.org/10.1353/soh.2022.0162.

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Gösweiner, Florian. "Abels, Gabriele/Eppler, Annegret (Eds.) 2015. Subnational Parliaments in the EU Multi-Level Parliamentary System: Taking Stock of the Post-Lisbon Era." Zeitschrift für Vergleichende Politikwissenschaft 11, no. 3 (2017): 431–33. http://dx.doi.org/10.1007/s12286-017-0343-z.

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Sharpless, Rebecca. "This Land is Herland: Gendered Activism in Oklahoma from the 1870s to the 2010s ed. by Sarah Eppler Janda and Patricia Loughlin." Southwestern Historical Quarterly 126, no. 3 (2023): 390–92. http://dx.doi.org/10.1353/swh.2023.0008.

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Bagheri-Sadeghi, Nojan, Brian T. Helenbrook, and Kenneth D. Visser. "Maximal power per device area of a ducted turbine." Wind Energy Science 6, no. 4 (2021): 1031–41. http://dx.doi.org/10.5194/wes-6-1031-2021.

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Abstract. The aerodynamic design of a ducted wind turbine for maximum total power coefficient was studied numerically using the axisymmetric Reynolds-averaged Navier–Stokes equations and an actuator disc model. The total power coefficient characterizes the rotor power per total device area rather than the rotor area. This is a useful metric to compare the performance of a ducted wind turbine with an open rotor and can be an important design objective in certain applications. The design variables included the duct length, the rotor thrust coefficient, the angle of attack of the duct cross section, the rotor gap, and the axial location of the rotor. The results indicated that there exists an upper limit for the total power coefficient of ducted wind turbines. Using an Eppler E423 airfoil as the duct cross section, an optimal total power coefficient of 0.70 was achieved at a duct length of about 15 % of the rotor diameter. The optimal thrust coefficient was approximately 0.9, independent of the duct length and in agreement with the axial momentum analysis. Similarly independent of duct length, the optimal normal rotor gap was found to be approximately the duct boundary layer thickness at the rotor. The optimal axial position of the rotor was near the rear of the duct but moved upstream with increasing duct length, while the optimal angle of attack of the duct cross section decreased.

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Cruz-Carvajal, Jonnathan J., Iván D. Hernández Umaña, and Edison J. Duque Oliva. "Estado actual del branding en las compañías spin-off y start-up académicas: caso universidades públicas en Colombia." Revista Perspectiva Empresarial 1, no. 1 (2014): 49. http://dx.doi.org/10.16967/rpe.8.

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Esta investigación tiene como fin describir el estado actual de los procesos de branding que efectúan las empresas tipo spin-off y start-upacadémicas en Colombia. Los hallazgos están basados en el estudio de caso de tres empresas tipo spin-off académico y tres start-upacadémico, provenientes de tres universidades públicas colombianas. Los datos son recopilados a través de entrevistas semiestructuradas aplicadas a los fundadores de las compañías, y a su vez analizados mediante la metodología de análisis de contenido cualitativo. Se empleó el modelo de análisis de branding para PYME descrito por Bresciani y Eppler (2010). Los resultados muestran la importancia de las actividades de branding para las empresas estudiadas. Nuevos factores fueron detectados como relevantes y particulares para los procesos de brandingen las spin-off y start-up académicas: la ausencia de departamentos de mercadeo, las actividades publicitarias como medio principal para efectuar presencia de marca, la figura del emprendedor como “representación viva” de la marca, los procesos de selección de personal y la importancia del respaldo de marca de la universidad. Se encontró que los factores que no han impulsado o permitido actividades de brandingen las empresas son la falta de recursos financieros, el desconocimiento del tema y la subvaloración de este. Finalmente se describió el proceso cíclico para el branding de la categoría de empresas analizadas.

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