Download or read book Profile Optimization Method for Robust Airfoil Shape Optimization in Viscous Flow written by Wu Li and published by . This book was released on 2003 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Profile Optimization Method for Robust Airfoil Shape Optimization in Viscous Flow written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-20 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: Simulation results obtained by using FUN2D for robust airfoil shape optimization in transonic viscous flow are included to show the potential of the profile optimization method for generating fairly smooth optimal airfoils with no off-design performance degradation. Li, Wu Langley Research Center NASA/TM-2003-212408, L-18283, NAS 1.15:212408
Download or read book Robust Airfoil Optimization to Achieve Consistent Drag Reduction Over a Mach Range written by Wu Li and published by . This book was released on 2001 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: We prove mathematically that in order to avoid point-optimization at the sampled design points for multipoint airfoil optimization, the number of design points must be greater than the number of free-design variables. To overcome point-optimization at the sampled design points, a robust airfoil optimization method (called the profile optimization method) is developed and analyzed. This optimization method aims at a consistent drag reduction over a given Mach range and has three advantages: (a) it prevents severe degradation in the off -design performance by using a smart descent direction in each optimization iteration, (b) there is no random airfoil shape distortion for any iterate it generates, and (c) it allows a designer to make a trade-off between a truly optimized airfoil and the amount of computing time consumed. For illustration purposes, we use the profile optimization method to solve a lift-constrained drag minimization problem for 2-D airfoil in Euler ow with 20 free-design variables. A comparison with other airfoil optimization methods is also included.
Download or read book Free form Airfoil Shape Optimization Under Uncertainty Using Maximum Expected Value and Second order Second moment Strategies written by and published by . This book was released on 2001 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: Free-form shape optimization of airfoils poses unexpected difficulties. Practical experience has indicated that a deterministic optimization for discrete operating conditions can result in dramatically inferior performance when the actual operating conditions are different from the - somewhat arbitrary - design values used for the optimization. Extensions to multi-point optimization have proven unable to adequately remedy this problem of "localized optimization" near the sampled operating conditions. This paper presents an intrinsically statistical approach and demonstrates how the shortcomings of multi-point optimization with respect to "localized optimization" can be overcome. The practical examples also reveal how the relative likelihood of each of the operating conditions is automatically taken into consideration during the optimization process. This is a key advantage over the use of multipoint methods.
Download or read book Aerodynamic Shape Optimization Using Control Theory written by James John Reuther and published by . This book was released on 1996 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: "Aerodynamic shape design has long persisted as a difficult scientific challenge due [sic] its highly nonlinear flow physics and daunting geometric complexity. However, with the emergence of Computational Fluid Dynamics (CFD) it has become possible to make accurate predictions of flows which are not dominated by viscous effects. It is thus worthwhile to explore the extension of CFD methods for flow analysis to the treatment of aerodynamic shape design. Two new aerodynamic shape design methods are developed which combine existing CFD technology, optimal control theory, and numerical optimization techniques. Flow analysis methods for the potential flow equation and the Euler equations form the basis of the two respective design methods. In each case, optimal control theory is used to derive the adjoint differential equations, the solution of which provides the necessary gradient information to a numerical optimization method much more efficiently then [sic] by conventional finite differencing. Each technique uses a quasi-Newton numerical optimization algorithm to drive an aerodynamic objective function toward a minimum. An analytic grid perturbation method is developed to modify body fitted meshes to accommodate shape changes during the design process. Both Hicks-Henne perturbation functions and B-spline control points are explored as suitable design variables. The new methods prove to be computationally efficient and robust, and can be used for practical airfoil design including geometric and aerodynamic constraints. Objective functions are chosen to allow both inverse design to a target pressure distribution and wave drag minimization. Several design cases are presented for each method illustrating its practicality and efficiency. These include non-lifting and lifting airfoils operating at both subsonic and transonic conditions."
Download or read book Using High Resolution Design Spaces for Aerodynamic Shape Optimization Under Uncertainty written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-12 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper explains why high resolution design spaces encourage traditional airfoil optimization algorithms to generate noisy shape modifications, which lead to inaccurate linear predictions of aerodynamic coefficients and potential failure of descent methods. By using auxiliary drag constraints for a simultaneous drag reduction at all design points and the least shape distortion to achieve the targeted drag reduction, an improved algorithm generates relatively smooth optimal airfoils with no severe off-design performance degradation over a range of flight conditions, in high resolution design spaces parameterized by cubic B-spline functions. Simulation results using FUN2D in Euler flows are included to show the capability of the robust aerodynamic shape optimization method over a range of flight conditions.Li, Wu and Padula, SharonLangley Research CenterHIGH RESOLUTION; SHAPE OPTIMIZATION; VARIATIONAL PRINCIPLES; PARAMETER IDENTIFICATION; ROBUSTNESS (MATHEMATICS); COMPUTATIONAL FLUID DYNAMICS; AIRFOILS; AERODYNAMIC COEFFICIENTS; DRAG REDUCTION; FLIGHT CONDITIONS; EULER EQUATIONS OF MOTION; LIFT; MULTIDISCIPLINARY DESIGN OPTIMIZATION; ALGORITHMS
Download or read book Adjoint based Airfoil Shape Optimization in Transonic Flow written by Joe-Ray Gramanzini and published by . This book was released on 2015 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The primary focus of this work is efficient aerodynamic shape optimization in transonic flow. Adjoint-based optimization techniques are employed on airfoil sections and evaluated in terms of computational accuracy as well as efficiency. This study examines two test cases proposed by the AIAA Aerodynamic Design Optimization Discussion Group. The first is a two-dimensional, transonic, inviscid, non-lifting optimization of a Modified-NACA 0012 airfoil. The second is a two-dimensional, transonic, viscous optimization problem using a RAE 2822 airfoil. The FUN3D CFD code of NASA Langley Research Center is used as the ow solver for the gradient-based optimization cases. Two shape parameterization techniques are employed to study their effect and the number of design variables on the final optimized shape: Multidisciplinary Aerodynamic-Structural Shape Optimization Using Deformation (MASSOUD) and the BandAids free-form deformation technique. For the two airfoil cases, angle of attack is treated as a global design variable. The thickness and camber distributions are the local design variables for MASSOUD, and selected airfoil surface grid points are the local design variables for BandAids. Using the MASSOUD technique, a drag reduction of 72.14% is achieved for the NACA 0012 case, reducing the total number of drag counts from 473.91 to 130.59. Employing the BandAids technique yields a 78.67% drag reduction, from 473.91 to 99.98. The RAE 2822 case exhibited a drag reduction from 217.79 to 132.79 counts, a 39.05% decrease using BandAids."--Abstract, page iii.
Download or read book An Optimal Control Theory Based Algorithm to Solve 2D Aerodynamic Shape Optimisation Problems for Inviscid and Viscous Flows written by S. Hiernaux and published by . This book was released on 2000 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the capacity of today's computers; one can envisage the resolution of shape optimization problems in aerodynamics. Nevertheless, optimization methods require many evaluations of different aerodynamic configurations, and so are much more expensive than a single analysis. It is therefore mandatory to find methods that evaluate aerodynamic functions and their gradient at the lowest possible computational cost; as well as fast and robust optimization methods.
Download or read book Recent Development of Aerodynamic Design Methodologies written by Kozo Fujii and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational Fluid Dynamics (CFD) has made remarkable progress in the last two decades and is becoming an important, if not inevitable, analytical tool for both fundamental and practical fluid dynamics research. The analysis of flow fields is important in the sense that it improves the researcher's understanding of the flow features. CFD analysis also indirectly helps the design of new aircraft and/or spacecraft. However, design methodologies are the real need for the development of aircraft or spacecraft. They directly contribute to the design process and can significantly shorten the design cycle. Although quite a few publications have been written on this subject, most of the methods proposed were not used in practice in the past due to an immature research level and restrictions due to the inadequate computing capabilities. With the progress of high-speed computers, the time has come for such methods to be used practically. There is strong evidence of a growing interest in the development and use of aerodynamic inverse design and optimization techniques. This is true, not only for aerospace industries, but also for any industries requiring fluid dynamic design. This clearly shows the matured engineering need for optimum aerodynamic shape design methodologies. Therefore, it seems timely to publish a book in which eminent researchers in this area can elaborate on their research efforts and discuss it in conjunction with other efforts.
Download or read book Using High Resolution Design Spaces for Aerodynamic Shape Optimization Under Uncertainty written by Wu Li and published by BiblioGov. This book was released on 2013-07 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper explains why high resolution design spaces encourage traditional airfoil optimization algorithms to generate noisy shape modifications, which lead to inaccurate linear predictions of aerodynamic coefficients and potential failure of descent methods. By using auxiliary drag constraints for a simultaneous drag reduction at all design points and the least shape distortion to achieve the targeted drag reduction, an improved algorithm generates relatively smooth optimal airfoils with no severe off-design performance degradation over a range of flight conditions, in high resolution design spaces parameterized by cubic B-spline functions. Simulation results using FUN2D in Euler flows are included to show the capability of the robust aerodynamic shape optimization method over a range of flight conditions.
Download or read book A Numerical Methodology for Aerodynamic Shape Optimization in Turbulent Flow Enabling Large Geometric Variation written by Lana Osusky and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Low Speed Aerodynamics written by Joseph Katz and published by Cambridge University Press. This book was released on 2001-02-05 with total page 636 pages. Available in PDF, EPUB and Kindle. Book excerpt: Low-speed aerodynamics is important in the design and operation of aircraft flying at low Mach number, and ground and marine vehicles. This 2001 book offers a modern treatment of the subject, both the theory of inviscid, incompressible, and irrotational aerodynamics and the computational techniques now available to solve complex problems. A unique feature of the text is that the computational approach (from a single vortex element to a three-dimensional panel formulation) is interwoven throughout. Thus, the reader can learn about classical methods of the past, while also learning how to use numerical methods to solve real-world aerodynamic problems. This second edition has a new chapter on the laminar boundary layer (emphasis on the viscous-inviscid coupling), the latest versions of computational techniques, and additional coverage of interaction problems. It includes a systematic treatment of two-dimensional panel methods and a detailed presentation of computational techniques for three-dimensional and unsteady flows. With extensive illustrations and examples, this book will be useful for senior and beginning graduate-level courses, as well as a helpful reference tool for practising engineers.
Download or read book Impact of Turbulence Models and Shape Parameterization on Robust Aerodynamic Shape Optimization written by Aslihan Vuruskan and published by . This book was released on 2020 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Aerodynamic design optimization is typically performed at fixed flight conditions, without considering the variation and uncertainty in operating conditions. The objective of robust aerodynamic optimization is to design an aerodynamic configuration, which will keep its optimum performance under varying conditions such as the speed of aircraft. The primary goal of this study was to investigate the impact of turbulence models used in RANS simulations on the 2-D airfoil and 3-D wing designs obtained with gradient-based deterministic and robust optimization in transonic, viscous, turbulent flows. The main contribution of this research to the aerodynamic design area was to quantify the impact of turbulence models (Spalart-Allmaras and Menter's Shear Stress Transport) and shape parameterization techniques (Hicks-Henne bump functions, B-Spline curves and Free-Form Deformation) on the computational cost, optimal shape, and its performance obtained with robust optimization under uncertainty. The effect of changing the relative weight of mean drag reduction and robustness measures used in the objective function was also investigated for the 3-D robust design. The robustness of the final design obtained with stochastic optimization approach was demonstrated over the Mach number range considered as the uncertain operating condition in this study. The results of the 2-D study show that the shape parameterization technique has a larger impact on the computational cost than the turbulence models in both deterministic and robust design. The results of the 3-D study show that the effect of the weight distribution in the objective function is more significant than the effect of turbulence model on the final design obtained with robust optimization below the design Mach number value. In general, robust optimization tends to reduce the impact of the turbulence model selection on the optimum shape and performance over the uncertain Mach number range considered, whereas the effect of the turbulence model becomes significant at off-design conditions for the optimal shapes obtained with deterministic design"--Abstract, page iii.
Download or read book Aerodynamic Shape Optimization of Two dimensional Airfoils Under Uncertain Conditions written by Luc Huyse and published by . This book was released on 2001 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Variational Method for Aerodynamic Optimization Using the Navier Stokes Equations written by and published by . This book was released on 1997 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report describes the formulation of an aerodynamic shape design methodology using a compressible viscous flow model based on the Reynolds Averaged Navier Stokes equations. The aerodynamic shape is described by a set of geometrical design variables. The design problem is formulated as an optimization problem stated in terms of an aerodynamic objective functional which has to be minimized. The design scheme employs a gradient based optimization algorithm in order to obtain the optimum values of the design variables. The gradient of the aerodynamic functional with respect to the design variables is computed by means of the variational method, which requires the solution of an adjoint problem. The formulation of the adjoint problem is described which leads to a set of adjoint equations and boundary conditions. Using the flow variables and the adjoint variables, an expression for the gradient has been constructed. Computational results are presented for an inverse problem of an airfoil. It will be shown that, starting from an initial geometry of the NACA 0012 airfoil, the target pressure distribution and geometry of a best fit of the RAE 2822 airfoil in a transonic flow condition has been reconstructed successfully.
Download or read book High fidelity Aerodynamic Shape Optimization for Natural Laminar Flow written by Ramy Rashad and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: To ensure the long-term sustainability of aviation, serious effort is underway to mitigate the escalating economic, environmental, and social concerns of the industry. Significant improvement to the energy efficiency of air transportation is required through the research and development of advanced and unconventional airframe and engine technologies. In the quest to reduce airframe drag, this thesis is concerned with the development and demonstration of an effective design tool for improving the aerodynamic efficiency of subsonic and transonic airfoils. The objective is to advance the state-of-the-art in high-fidelity aerodynamic shape optimization by incorporating and exploiting the phenomenon of laminar-turbulent transition in an efficient manner. A framework for the design and optimization of Natural Laminar Flow (NLF) airfoils is developed and demonstrated with transition prediction capable of accounting for the effects of Reynolds number, freestream turbulence intensity, Mach number, and pressure gradients. First, a two-dimensional Reynolds-averaged Navier-Stokes (RANS) flow solver has been extended to incorporate an iterative laminar-turbulent transition prediction methodology. The natural transition locations due to Tollmien-Schlichting instabilities are predicted using the simplified e^N envelope method of Drela and Giles or, alternatively, the compressible form of the Arnal-Habiballah-Delcourt criterion. The boundary-layer properties are obtained directly from the Navier-Stokes flow solution, and the transition to turbulent flow is modeled using an intermittency function in conjunction with the Spalart-Allmaras turbulence model. The RANS solver is subsequently employed in a gradient-based sequential quadratic programming shape optimization framework. The laminar-turbulent transition criteria are tightly coupled into the objective and gradient evaluations. The gradients are obtained using a new augmented discrete-adjoint formulation for non-local transition criteria. Using the e^N transition criterion, the proposed framework is applied to the single and multipoint optimization of subsonic and transonic airfoils, leading to robust NLF designs. The aerodynamic design requirements over a range of cruise flight conditions are cast into a multipoint optimization problem through a composite objective defined using a weighted integral of the operating points. To study and quantify off-design performance, a Pareto front is formed using a weighted objective combining free-transition and fully-turbulent operating conditions. Next we examine the sensitivity of NLF design to the freestream disturbance environment, highlighting the on- and off-design performance at different critical N-factors. Finally, we propose and demonstrate a technique to enable the design of airfoils with robust performance over a range of critical N-factors.
Download or read book Shape Optimization of Airfoils Without and with Ground Effect Using a Multi objective Genetic Algorithm written by Yilei He and published by . This book was released on 2014 with total page 93 pages. Available in PDF, EPUB and Kindle. Book excerpt: The focus of this thesis is on shape optimization using a genetic algorithm. A multi-objective genetic algorithm (MOGA) is employed to optimize the shape of an airfoil to improve its lift and drag characteristics, in particular to achieve two objectives simultaneously that is to increase its lift as well as its lift to drag ratio. The commercially available software FLUENT is employed to calculate the flow field on an adaptive structured mesh, which is generated by the commercial mesh generating software ICEM. The flow field is calculated using the Reynolds-Averaged Navier-Stokes (RANS) equations in conjunction with a two equation k-[omega] SST turbulence model. Bezier Curves are employed to generate airfoil shapes for a particular generation of the genetic algorithm; these shapes are tested by MOGA in conjunction with FLUENT to evaluate their fitness by calculating their lift and lift to drag ratio. The process is continued for a number of generations until the lift and lift to drag ratios converge to their optimal values. MOGA optimization method is used to optimize a well-known wind turbine airfoil S809 and NACA 4412 airfoil in ground effect. The results show significant improvement in both the lift coefficient and lift-to-drag ratio of the optimized airfoil compared to the original airfoil.
