Author: Stuart E. Rogers
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Vivek Lall
Publisher:
ISBN:
Category : Aerofoils
Languages : en
Pages : 440

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Author: Philippe Godin
Publisher: Library and Archives Canada = Bibliothèque et Archives Canada
ISBN: 9780612942325
Category : Lift (Aerodynamics)
Languages : en
Pages : 272

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Book Description
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.

Author: Alain Dervieux
Publisher: Springer Science & Business Media
ISBN: 3322898598
Category : Technology & Engineering
Languages : en
Pages : 580

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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

Author: American Institute of Aeronautics and Astronautics
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 1184

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Author: Omer Ali El-Sayed
Publisher:
ISBN:
Category :
Languages : en
Pages : 256

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The flow-field around a multi-element airfoil with leading-edge slat and trailing edge flap in landing configuration was performed as well as the prediction of the time dependent flow over a NACA 0012 airfoil. The two dimensional incompressible Navier-Stokes equations with a numerical method based on the pseudo compressibility approach was developed to simulate viscous turbulent flow around single and multi-element airfoils. The algorithm uses upwind-biased scheme of third order accuracy for the calculation of the inviscid fluxes, while a second order central differencing in sued for viscous fluxes, the equations are solved using Lower-Upper Symmetric Gauss Seidel (LU-SGS) schemes. The grids around multi-element airfoil are efficiently generated using a multi-block structure technique. The Baldwin-Lomax algebraic turbulence model is used to consider the effect of turbulence. Computed results for the studied cases were compared with experimental data in terms of surface pressure and lift coefficients which show reasonable agreement.

Author: S. L. Woodruff
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Josef Ballmann
Publisher: Springer Science & Business Media
ISBN: 3540448667
Category : Technology & Engineering
Languages : en
Pages : 396

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The research work of the collaborative research center SFB401 Flow Modulation and Fluid-Structure Interaction at Airplane Wings at the Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen, which is reported in this book, was pos sible due to the financial support of the Deutsche Forschungsgemeinschaft (DFG). The proposal has been approved after evaluation by the referees of DFG selected from other universities and industry, which is gratefully acknowledged. The work is still in progress and now approved to continue until the end of year 2005. More than 50 scientists from universities of the United States, Russia, France, Italy, Japan, Great Britain, Sweden, Netherlands, Switzerland, Austria and research orga nizations NASA, ONERA, NLR, DLR could be invited and have visited the research center, gave seminars on their research on related topics and some of them stayed longer for joined work. Besides its scientific value, also the importance of the pro gram for scientific educa tion becomes evident by looking at the numbers of completed theses, which are up to now about 15 doctoral theses, 40 diploma theses and 70 study theses. The authors of this book acknowledge the valuable support coming from all these persons and institutions. They are especially grateful to the referees having reviewed this work, A. Cohen (Universite Pierre et Marie Curie), J. Cooper (Manchester School of Engineering), W. Devenport (Virginia Tech.), M. Drela (MIT), F. Gern (Avionics Specialties Inc.), A. Griewank (TU Dresden), H. Hönlinger (DLR), P.

Author: Zaffar Mahmood
Publisher:
ISBN:
Category :
Languages : en
Pages : 485

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The present research work has been concerned with the measurement and computation of incompressible turbulent flow development around single and multi-element aerofoils. Detailed measurements of the mean velocity and turbulence stress fields over NACA 4412 aerofoil and NACA 4415 flap section are made using a flying hot-wire system. The results are analyzed and characteristics of the mean flow and turbulence field development as a function of angle of attack and flap gap/deflection are presented. The results indicate increasing intermittent separation over single aerofoil with increase in angle of incidence. A large separation is observed for multi-element cases at large incidences (......) accompanied by high turbulence levels observed in the separated shear layers. The effectiveness of the flap in the multi-element aerofoil as a source of additional lift is observed only at low angles of attack (......) and with moderate flap deflections only. The numerical computations are carried out by solving Reynolds-averaged, Navier-Stokes equations employing both the standard .... and Reynolds stress (RSM) turbulence models using a commercially available CFD package. The problems associated with geometry complexity, deriving from closely coupled configuration of multi-element aerofoils, are overcome by employing structured computational grids using curvilinear coordinates. The comparison of computations with experimental results for single element aerofoil gives reasonable accuracy at low angles of attack (....) using both turbulence models. However, for the multi-element aerofoil discrepancies are observed near the trailing edge of the main aerofoil at large incidences even with RSM, implying the insufficient and simplifying assumptions used in modeled terms which are unable to deal with complex flow features observed in the present investigation. It is recommended that the various modeled terms (such as pressure-strain) be reexamined to take into account the curved mixing layers.

Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 464

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