Download or read book Prediction of Airfoil Characteristics with Higher Order Turbulence Models written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-10 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study focuses on the prediction of airfoil characteristics, including lift and drag over a range of Reynolds numbers. Two different turbulence models, which represent two different types of models, are tested. The first is a standard isotropic eddy-viscosity two-equation model, and the second is an explicit algebraic stress model (EASM). The turbulent flow field over a general-aviation airfoil (GA(W)-2) at three Reynolds numbers is studied. At each Reynolds number, predicted lift and drag values at different angles of attack are compared with experimental results, and predicted variations of stall locations with Reynolds number are compared with experimental data. Finally, the size of the separation zone predicted by each model is analyzed, and correlated with the behavior of the lift coefficient near stall. In summary, the EASM model is able to predict the lift and drag coefficients over a wider range of angles of attack than the two-equation model for the three Reynolds numbers studied. However, both models are unable to predict the correct lift and drag behavior near the stall angle, and for the lowest Reynolds number case, the two-equation model did not predict separation on the airfoil near stall. Gatski, Thomas B. Langley Research Center RTOP 505-59-50-05...
Download or read book Prediction of Airfoil Characteristics With Higher Order Turbulence Models written by Thomas B. Gatski and published by . This book was released on 1996 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study focuses on the prediction of airfoil characteristics, including lift and drag over a range of Reynolds numbers. Two different turbulence models, which represent two different types of models, are tested. The first is a standard isotropic eddy-viscosity two-equation model, and the second is an explicit algebraic stress model (EASM). The turbulent flow field over a general-aviation airfoil (GA(W)-2) at three Reynolds numbers is studied. At each Reynolds number, predicted lift and drag values at different angles of attack are compared with experimental results, and predicted variations of stall locations with Reynolds number are compared with experimental data. Finally, the size of the separation zone predicted by each model is analyzed, and correlated with the behavior of the lift coefficient near stall. In summary, the EASM model is able to predict the lift and drag coefficients over a wider range of angles of attack than the two-equation model for the three Reynolds numbers studied. However, both models are unable to predict the correct lift and drag behavior near the stall angle, and for the lowest Reynolds number case, the two-equation model did not predict separation on the airfoil near stall.
Download or read book Comparisons of Theoretical Methods for Predicting Airfoil Aerodynamic Characteristics written by and published by . This book was released on 2010 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: A number of airfoils intended for VTOL/Rotorcraft applications were tested in the Penn State Low-Speed, Low-Turbulence Wind Tunnel, and the results of these tests compared with those predicted using several well-known theoretical methods. The airfoils considered are the E 387 and the S406, S407, S411, S414, and the S415, and the theoretical methods used are the potential-flow/integral boundary-layer methods, PROFIL07 and XFOIL 6.94, the Euler solver/integral boundary-layer method, MSES 3.05, and the Reynolds-averaged Navier-Stokes solver, OVERFLOW 2.1ae. In addition, several cases were considered using the Navier-Stokes solver, FLUENT 12.1.2, which incorporates the Langtry-Menter four-equation turbulence model that has demonstrated some capability of capturing the transition process. While none of the methods considered was consistently the best overall, the drag predictions of the codes incorporating boundary-layer methods generally agreed better with the experimental results than did those of the Navier-Stokes solvers. All of the theoretical methods frequently over-predicted the maximum lift coefficient, although an empirical criterion developed for use with PROFIL yielded reasonably close agreement with the measurements. The Langtry-Menter turbulence model employed in FLUENT 12.1.2 shows promise in being able to model the transition process, including the development of laminar separation bubbles.
Download or read book Computational Prediction of Flow and Aerodynamic Characteristics for an Elliptic Airfoil at Low Reynolds Number written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Lifting surfaces of unmanned aerial vehicles (UAV) are often operated in low Reynolds number (Re) ranges, wherein the transition of boundary layer from laminar-toturbulent plays a more significant role than in high-Re aerodynamics applications. This poses a challenge for traditional computational fluid dynamics (CFD) simulations, since typical modeling approaches assume either fully laminar or fully turbulent flow. In particular, the boundary layer state must be accurately predicted to successfully determine the separation behavior which significantly influences the aerodynamic characteristics of the airfoil. Reynolds-averaged Navier-Stokes (RANS) based CFD simulations of an elliptic airfoil are performed for time-varying angles of attack, and results are used to elucidate relevant flow physics and aerodynamic data for an elliptic airfoil under realistic operating conditions. Results are also used to evaluate the performance of several different RANS-based turbulence modeling approaches for this class of flowfield
Download or read book Advances in Turbulence VI written by S. Gavrilakis and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 643 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Turbulence VI presents an update on the state of turbulence research with some bias towards research in Europe, since it represents an almost complete collection of the paper presentations at the Sixth European Turbulence Conference, sponsored by EUROMECH, ERCOFTAC and COST, and held at the Swiss Federal Institute of Technology in Lausanne, July 2-5, 1996. The problem of transition, together with the structural description of turbulence, and the scaling laws of fully developed turbulence have continued to receive most attention by the research community and much progress has been made since the last European Turbulence Conference in 1994. The volume is thus geared towards specialists in the area of flow turbulence who could not attend the conference, as well as anybody who wishes quickly to assess the most active current research areas and the groups associated with them.
Download or read book NASA Technical Memorandum written by and published by . This book was released on 1994 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Predicting Aerodynamic Characteristic of Typical Wind Turbine Airfoils Using CFD written by and published by . This book was released on 1997 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt: An investigation was conducted into the capabilities and accuracy of a representative computational fluid dynamics code to predict the flow field and aerodynamic characteristics of typical wind-turbine airfoils. Comparisons of the computed pressure and aerodynamic coefficients were made with wind tunnel data. This work highlights two areas in CFD that require further investigation and development in order to enable accurate numerical simulations of flow about current generation wind-turbine airfoils: transition prediction and turbulence modeling. The results show that the laminar-to turbulent transition point must be modeled correctly to get accurate simulations for attached flow. Calculations also show that the standard turbulence model used in most commercial CFD codes, the k-e model, is not appropriate at angles of attack with flow separation. 14 refs., 28 figs., 4 tabs.
Download or read book Advances in wind turbine blade design and materials written by W.A. Timmer and published by Elsevier Inc. Chapters. This book was released on 2013-10-31 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: This chapter focuses on airfoils for wind turbine blades and their characteristics. The use of panel codes such as XFOIL and RFOIL and CFD codes for the prediction of airfoil characteristics is briefly described. The chapter then discusses the requirements for wind turbine blade airfoils and the effect of leading edge roughness and Reynolds number. After a description of how airfoils can be tested the chapter discusses methods to represent airfoil characteristics at high angles of attack. A number of methods for correcting characteristics for the effect of three-dimensional flow on the blade are presented. The chapter then discusses ways to establish a data set for blade design and concludes with a view on future research in the field of wind turbine blade airfoils.
Download or read book Advances in Energy Science and Equipment Engineering written by Shiquan Zhou and published by CRC Press. This book was released on 2015-11-05 with total page 2914 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Energy Equipment Science and Engineering contains selected papers from the 2015 International Conference on Energy Equipment Science and Engineering (ICEESE 2015, Guangzhou, China, 30-31 May 2015). The topics covered include:- Advanced design technology- Energy and chemical engineering- Energy and environmental engineering- Energy scien
Download or read book Computation and Comparison of Efficient Turbulence Models for Aeronautics European Research Project ETMA written by Alain Dervieux and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 580 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains contributions to the BRITE-EURAM 3rd Framework Programme ETMA and extended articles of the TMA-Workshop. It focusses on turbulence modelling techniques suitable to use in typical flow configurations, with emphasis on compressibility effects and inherent unsteadiness. These methodologies are applied to the Navier-Stokes equations, involving various turbulence modelling levels from algebraic to RSM. Basic turbulent flows in aeronautics are considered; mixing layers, wall-flows (flat-plate, backward-facing step, ramp, bump), and more complex configurations (bump, aerofoil). A critical assessment of the turbulence modelling performances is offered, based on previous results and on the experimental data-base of this research programme. The ETMA results figure in the data-base constituted by all partners and organized by INRIA
Download or read book AIAA Journal written by American Institute of Aeronautics and Astronautics and published by . This book was released on 2007 with total page 960 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Summary of Low Speed Airfoil Data written by Michael S. Selig and published by Soartech. This book was released on 1995 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Turbulence Model Evaluation for the Prediction of Flows Over a Super Critical Airfoil with Deflected Aileron at High Reynolds Number written by W. Kelly Londenberg and published by . This book was released on 1993 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Assessment of Higher Order Turbulence Models for Complex Two and Three dimensional Flowfields written by and published by . This book was released on 1992 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book 05 5258 05 5393 written by and published by . This book was released on 2005 with total page 484 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Turbulence Modeling for High lift Multi element Airfoil Configurations microform written by Philippe Godin and published by Library and Archives Canada = Bibliothèque et Archives Canada. This book was released on 2004 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study provides a detailed comparison of two turbulence closures for aerodynamic flows around high-lift airfoils; the first based on turbulent viscosity and the second on the algebraic Reynolds-stress approximation. A detailed analysis of their derivation helps shed light on their inherent limitations in predicting complex flow phenomena such as confluent boundary layers and flow separation found in typical take-off and landing conditions. One of each of the following categories: one-equation, two-equation, IARSM and EARSM is selected and compared on several low-speed high-lift configurations. Comparisons to experimental data for both mean flow and turbulence quantities are provided for all cases studied. Amongst the turbulent viscosity models coded and studied are the Spalart-Allmaras, Baldwin-Barth, Wilcox k - o and Menter's Shear Stress Transport model. A parameter study based on different pressure-strain correlations and dissipation models (or near-wall treatment) is included when studying the algebraic Reynolds-stress models for both the explicit (EARSM) and the more traditional or implicit (IARSM) forms. Results are generally very promising and of sufficient accuracy for engineering interest. Overall, the study indicates that for flows around low-speed high-lift airfoils, the algebraic Reynolds-stress construct does not represent a higher level of description than the eddy viscosity models since it fails to improve on accuracy. The basic underlying assumption of weak-equilibrium in algebraic Reynolds-stress models is outperformed by well calibrated eddy-viscosity models.
