Download or read book Numerical Study of Separated Turbulent Flow Over Airfoils written by Ananthanarayanan Sugavanam and published by . This book was released on 1979 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Study of Separated Turbulent Flows written by and published by . This book was released on 1974 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent boundary layer separation was studied numerically using a special code to integrate the model equations for transient two-dimensional turbulent flow. For three calculations, separation was induced by interaction of a boundary layer with oblique shock waves; for three others, separation was caused by flow into the compression corner formed by an adiabatic flat-plate and ramp. In every case the free-stream Mach number was 2.96, the Reynolds number based on boundary layer thickness just upstream of the interaction region ranged from 1/4 to 1 million, and the static pressure rose by a factor of either 3.7 or 5.1.

Download or read book Turbulent and Separated Flow Over Multi element Aerofoils written by Zaffar Mahmood and published by . This book was released on 1995 with total page 485 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Separation of Flow written by Paul K. Chang and published by Elsevier. This book was released on 2014-06-28 with total page 800 pages. Available in PDF, EPUB and Kindle. Book excerpt: Interdisciplinary and Advanced Topics in Science and Engineering, Volume 3: Separation of Flow presents the problem of the separation of fluid flow. This book provides information covering the fields of basic physical processes, analyses, and experiments concerning flow separation. Organized into 12 chapters, this volume begins with an overview of the flow separation on the body surface as discusses in various classical examples. This text then examines the analytical and experimental results of the laminar boundary layer of steady, two-dimensional flows in the subsonic speed range. Other chapters consider the study of flow separation on the two-dimensional body, flow separation on three-dimensional body shape and particularly on bodies of revolution. This book discusses as well the analytical solutions of the unsteady flow separation. The final chapter deals with the purpose of separation flow control to raise efficiency or to enhance the performance of vehicles and fluid machineries involving various engineering applications. This book is a valuable resource for engineers.

Download or read book Elements of Vorticity Aerodynamics written by James C. Wu and published by Springer. This book was released on 2017-12-27 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book opens with a discussion of the vorticity-dynamic formulation of the low Mach number viscous flow problem. It examines the physical aspects of the velocity and the vorticity fields, their instantaneous relationship, and the transport of vorticity in viscous fluids for steady and unsteady flows. Subsequently, using classical analyses it explores the mathematical aspects of vorticity dynamics and issues of initial and boundary conditions for the viscous flow problem. It also includes the evolution of the vorticity field which surrounds and trails behind airfoils and wings, generalizations of Helmholtz’ vortex theorems and the Biot-Savart Law. The book introduces a theorem that relates the aerodynamic force to the vorticity moment and reviews the applications of the theorem. Further, it presents interpretations of the Kutta-Joukowski theorem and Prandtl’s lifting line theory for vorticity dynamics and discusses wake integral methods. The virtual-mass effect is shown to be the seminal event in unsteady aerodynamics and a simple approach for evaluating virtual-mass forces on the basis of vorticity dynamics is presented. The book presents a modern viewpoint on vorticity dynamics as the framework for understanding and establishing the fundamental principles of viscous and unsteady aerodynamics. It is intended for graduate-level students of classical aerodynamics and researchers exploring the frontiers of fully unsteady and non-streamlined aerodynamics.

Download or read book Numerical Study of Separated Turbulent Flows written by and published by . This book was released on 1974 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent boundary layer separation was studied numerically using a special code to integrate the model equations for transient two-dimensional turbulent flow. For three calculations, separation was induced by interaction of a boundary layer with oblique shock waves; for three others, separation was caused by flow into the compression corner formed by an adiabatic flat-plate and ramp. In every case the free-stream Mach number was 2.96, the Reynolds number based on boundary layer thickness just upstream of the interaction region ranged from 1/4 to 1 million, and the static pressure rose by a factor of either 3.7 or 5.1.

Download or read book Two Dimensional Separated Flows written by S. M. Belotserkovsky and published by CRC Press. This book was released on 1992-11-30 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-Dimensional Separated Flows provides a systematic presentation of the theory of separated flow around bodies. The main classes of aerodynamic problems of plane-parallel flow around bodies are described, and the steady aerodynamic, unsteady aerodynamic, and statistical characteristics of a trailing wake are determined. Numerical methods based on the synthesis of models for non-viscous incompressible flow and boundary layer, algorithms, examples, and systematic comparisons are presented. The book also includes numerical results for the problem of separated flow around fixed, oscillating, and rotating cylinders, in addition to results for separated flow around an aerofoil over a wide range of angles. Two-Dimensional Separated Flows will benefit researchers and students studying aerodynamics, aircraft dynamics, aeroelasticity, and the aerodynamics of building structures.

Download or read book Numerical Simulation of Turbulent Flow Over an Airfoil Via Additive Turbulent Decomposition written by Yunpeng Yang and published by . This book was released on 1996 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Numerical Study of the Turbulent Flow Around Airfoils written by Vincent DeHenau and published by . This book was released on 1987 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Numerical Study of the Flow Past an Isolated Airfoil with Separation written by Chae-Myung Rhie and published by . This book was released on 1981 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Law of Incipient Separation for Turbulent Flows Over Airfoils as Inferred by RANS written by Shao-Chi Huang and published by . This book was released on 2021 with total page 53 pages. Available in PDF, EPUB and Kindle. Book excerpt: In a recent study, Lu, Aithal & Ferrante (AIAA J., 2021) have discovered the law of incipient separation for curved ramps that predicts the incipiency of flow separation by knowing only a few geometrical parameters of the ramp and the Reynolds number of the incoming flow. In the present study, we have searched for a similar law to predict the separation of the turbulent flow over airfoils. With that goal, we have conducted two-dimensional Reynolds averaged Navier-Stokes (RANS) wall-resolved simulations of incompressible turbulent flows over several airfoils over a range of angles of attack. Along the study, we have carried out verification and validation of RANS using the Spalart-Allmaras model against the experimental measurements by Wadcock (NASA-CR-177450, 1987) for the turbulent flow over a NACA4412 airfoil at a Reynolds number based on the airfoil chord length of Re = 1640000. From such comparison, we have found that although the RANS prediction fails when the airfoil approaches its maximum lift (alpha

Download or read book Low Reynolds Number written by Mustafa Serdar Genç and published by BoD – Books on Demand. This book was released on 2012-04-04 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reports the latest development and trends in the low Re number aerodynamics, transition from laminar to turbulence, unsteady low Reynolds number flows, experimental studies, numerical transition modelling, control of low Re number flows, and MAV wing aerodynamics. The contributors to each chapter are fluid mechanics and aerodynamics scientists and engineers with strong expertise in their respective fields. As a whole, the studies presented here reveal important new directions toward the realization of applications of MAV and wind turbine blades.

Download or read book Numerical Simulation for Flow Separation Around a 2 D Airfoil written by Shutian Deng and published by . This book was released on 2001 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper carries out numerical study of the flow separations around NACA 0012 airfoil at large angles of attack. Flow separation introduces two major effects: sudden loss of lift and generation of aerodynamic noise. These two factors are highly concerned on the aircraft designation. This study gives a detail picture of flow separation. As the problems caused by flow separation are complicated, the spatial and temporal complexity makes it difficult to access by conventional experiment methods. In the presented work, the numerical investigation results from solving the time-dependent Navier Stokes equations in the generalized curvilinear coordinates. Using a fourth order centered compact scheme for spatial discretization facilitates high resolution of the flow field, which will be neglected if using low-order numerical schemes. To avoid possible non-physical wave reflection, the non-reflecting boundary conditions are used at far-field and outlet boundary. Complex flow separation, vortex shedding, vortex merging, and vortex paring are observed in the computational results. The main purpose of this paper is to provide more detailed information of the flow separation.

Download or read book A Numerical Simulation of Flow Over a NACA0025 Airfoil Using Large Eddy Simulation Turbulence Models written by Babak Babaee Owlam and published by . This book was released on 2008 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ability of computational fluid dynamic (CFD) to predict critical flow characteristics has always been questionable. Flow separation over lifting surfaces such as airfoils are one of the critical features which can significantly deteriorate their aerodynamic performances. The purpose of this research is to evaluate the accuracy of two CFD methods in predicting the flow separation over a NACA0025 airfoil at low Reynolds numbers. The first code is an in-house code which is based on a 3D compressible Navier-Stokes solver with preconditioning and self-adaptive upwinding methods. The second code is the commercial FLUENT software. In order to accurately simulate the laminar boundary layer separation, the Large Eddy Simulation (LES) method is used for turbulence modeling of both codes. Results comparison shows that Fluent is not able to capture this feature. In addition the results are also compared with another similar numerical simulation and validated with available experimental data.

Download or read book The Numerical Solution of Incompressible Turbulent Flow Over Airfoils written by Harwood Allan Hegna and published by . This book was released on 1981 with total page 171 pages. Available in PDF, EPUB and Kindle. Book excerpt: Numerical solutions are obtained for two-dimensional incompressible turbulent viscous flow over airfoils of arbitrary geometry. A body-fitted coordinate system is numerically transformed to a rectangular grid in the computational plane. The time dependent Reynolds averaged Navier-Stokes equations in the primitive variables of velocity and pressure are used. Turbulence is modelled with an algebraic eddy viscosity technique modified for separated adverse pressure gradient flows. The set of transformed partial differential equations is solved with an implicit finite difference method. Numerical solutions for a NACA 0012 airfoil near stall at a chord Reynolds number of 170,000 are favorably compared with surface pressure and velocity field measurements. A small laminar separation bubble near the suction pressure peak is observed. Computed lift and drag coefficients agree well with experimental values. (Author).

Download or read book An Evaluation of Four Methods of Numerical Analysis for Two Dimensional Airfoil Flows Revision written by R. Burke and published by . This book was released on 1985 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: Four computer programs for analyzing the inviscid and boundary layer flow over two dimensional airfoils are exercised in comparisons against experimental data from two wind tunnel studies. The solution method of each computer program is discussed, followed by a description of the airfoil geometries used in the model comparisons. Measured values of pressure distribution, turbulent separation point, and boundary layer properties are compared against predicted values.

Download or read book Direct Numerical Simulation of a Spatially Developing Turbulent Boundary Layer Separating Over a Curved Wall written by Abhiram B. Aithal and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flow separation is encountered in many engineering devices, e.g., turbines, diffusers, wings and aftbodies of aircrafts. The physical mechanisms of separated turbulent boundary layers over curved walls are not yet well understood. The main objectives of the present study are to: (i) develop an efficient numerical methodology to perform direct numerical simulations (DNS) of spatially-developing turbulent boundary layers (SDTBLs) over curved walls, and (ii) enhance our knowledge on the dynamics of turbulence in SDTBLs separating over curved walls. To achieve these objectives, we have developed a new pressure-correction method, called FastRK3, for simulating incompressible flows over curved walls. FastRK3 solves the incompressible Navier-Stokes (NS) equations written in orthogonal curvilinear coordinates. The orthogonal formulation of the NS equations substantially reduces the computational cost of the flow solver and the numerical stencils of its second-order finite difference discretization mirror that of the Cartesian formulation. This property allows us to develop an FFT-based Poisson solver for pressure, called FastPoc, for those cases where the components of the metric tensor are independent of one spatial direction: surfaces of linear translation (e.g., curved ramps and bumps) and surfaces of revolution (e.g., axisymmetric shapes). Our results show that the new FFT-based Poisson solver, FastPoc, is thirty to sixty times faster than the multigrid-based linear solver, and the new flow solver, FastRK3, is overall four to seven times faster when using FastPoc rather than multigrid. FastRK3 is an explicit, three-stage, third-order Runge-Kutta based projection-method which requires solving the Poisson equation for pressure only once per time step. We show theoretically and numerically that (i) FastRK3 has the same temporal order of accuracy for pressure and velocity as the standard RK3 method for both free-shear and wall-bounded flows when the RK3 coefficients and the pressure extrapolation scheme satisfy specific conditions herein theoretically derived, (ii) FastRK3 is third-order accurate in time for velocity and second-order accurate in time for pressure for free-shear flows, and (iii) FastRK3 is second-order accurate in time for velocity and pressure for `stiff' wall-bounded flows. In summary, given that the computational mesh satisfies the property of orthogonality, FastRK3 simulates flows over curved walls with second-order accuracy in both space and time. Using FastRK3, we perform DNS of a SDTBL separating over a curved wall. We validate FastRK3 by comparing our numerical results with published experiments. For the first time, we derive the budget equations of the turbulence kinetic energy and of the Reynolds stresses in orthogonal coordinates, and report the results from our DNS. We study the dynamics of turbulence of the separated flow over the curved wall by analyzing these budget equations. Our analysis shows that, in the separated region over the curved ramp, the TKE production occurs through the production of (u2) as well as (v2) in contrast to a ZPG SDTBL where the TKE production is mostly through the production of (u2). In the curved ramp region, the viscous diffusion and dissipation of (v2) and (uv) are not zero at the wall, unlike that for both a ZPG SDTBL over a flat-plate as well as a pressure-gradient induced turbulent flow separation over a flat plate. And, the curved ramp region of the flow is characterized by enhanced transport of the Reynolds stresses compared to those of the upstream ZPG SDTBL due to the mixing layer created in the flow by the flow separation. Finally, our results have shown, for the first time, that the Reynolds stress profiles and budgets in the orthogonal curvilinear coordinates are very similar to those in the APG region of the 'pressure-gradient induced flow separation' in a flat-plate turbulent boundary layer. Such a comparison is only possible because (i) we employ a structured orthogonal grid over the curved ramp in our simulations, and (ii) FastRK3 solves the governing equations written in orthogonal curvilinear coordinates.