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Book High fidelity Aerodynamic Shape Optimization for Natural Laminar Flow

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.

Book Aerodynamic Shape Optimization of Complex Aircraft Configurations Via an Adjoint Formulation

Download or read book Aerodynamic Shape Optimization of Complex Aircraft Configurations Via an Adjoint Formulation written by James Reuther and published by . This book was released on 1996 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: "This work describes the implementation of optimization techniques based on control theory for complex aircraft configurations. Here control theory is employed to derive the adjoint differential equations, the solution of which allows for a drastic reduction in computational costs over previous design methods [13, 12, 43, 38]. In our earlier studies [19, 20, 22, 23, 39, 25, 40, 41, 42] it was shown that this method could be used to devise effective optimization procedures for airfoils, wings and wing-bodies subject to either analytic or arbitrary meshes. Design formulations for both potential flows and flows governed by the Euler equations have been demonstrated, showing that such methods can be devised for various governing equations [39, 25]. In our most recent works [40, 42] the method was extended to treat wing-body configurations with a large number of mesh points, verifying that significant computational savings can be gained for practical design problems. In this paper the method is extended for the Euler equations to treat complete aircraft configurations via a new multiblock implementation. New elements include a multiblock-multigrid flow solver, a multiblock-multigrid adjoint solver, and a multiblock mesh perturbation scheme. Two design examples are presented in which the new method is used for the wing redesign of a transonic business jet."

Book Aerodynamic Shape Optimization Using Control Theory

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."

Book Aerodynamic Shape Optimization of Two dimensional Airfoils Under Uncertain Conditions

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:

Book Aerodynamic Shape Optimization Via Discrete Adjoint Formulation Using Euler Equations on Unstructured Grids

Download or read book Aerodynamic Shape Optimization Via Discrete Adjoint Formulation Using Euler Equations on Unstructured Grids written by Bijoyendra Nath and published by . This book was released on 1998 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: For the optimization process, a constrained nonlinear programming package which uses a sequential quadratic programming algorithm is used. This study presents the process of analytically obtaining the exact discrete sensitivity derivatives and computationally cost-effective algorithms to efficiently use them in a design environment. Storage issues are circumvented by developing algorithms which perform matrix-vector operations during the construction itself. To validate the unstructured shape optimization procedure, an arbitrary symmetrical airfoil is optimized in an inviscid transonic flow regime.

Book The Discrete Adjoint Approach to Aerodynamic Shape Optimization

Download or read book The Discrete Adjoint Approach to Aerodynamic Shape Optimization written by Siva Kumaran Nadarajah and published by . This book was released on 2003 with total page 253 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Recent Development of Aerodynamic Design Methodologies

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.

Book Natural Laminar Flow and Laminar Flow Control

Download or read book Natural Laminar Flow and Laminar Flow Control written by R. W. Barnwell and published by . This book was released on 1992 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research on laminar flow and its transition to turbulent flow has been an important part of fluid dynamics research during the last sixty years. Since transition impacts, in some way, every aspect of aircraft performance, this emphasis is not only understandable but should continue well into the future. The delay of transition through the use of a favorable pressure gradient by proper body shaping (natural laminar flow) or the use of a small amount of suction (laminar flow control) was recognized even in the early 1930s and rapidly became the foundation of much of the laminar flow research in the U.S. and abroad. As one would expect, there have been many approaches, both theoretical and experimental, employed to achieve the substantial progress made to date. Boundary layer stability theories have been formu lated and calibrated by a good deal of wind tunnel and flight experiments. New laminar now airfoils and wings have been designed and many have been employed in aircraft designs. While the early research was, of necessity, concerned with the design of subsonic aircraft interest has steadily moved to higher speeds including those appropriate to planetary entry. Clearly, there have been substantial advances in our understanding of transition physics and in the development and application of transition prediction methodolo gies to the design of aircraft.

Book An Approach to the Constrained Design of Natural Laminar Flow Airfoils

Download or read book An Approach to the Constrained Design of Natural Laminar Flow Airfoils written by and published by . This book was released on 1997 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Adjoint based Airfoil Shape Optimization in Transonic Flow

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.

Book Using High Resolution Design Spaces for Aerodynamic Shape Optimization Under Uncertainty

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

Book Numerical Shape Optimization of Airfoils with Practical Aerodynamic Design Requirements

Download or read book Numerical Shape Optimization of Airfoils with Practical Aerodynamic Design Requirements written by Jens Howard Peter Buckley and published by . This book was released on 2009 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: Practical aerodynamic shape design problems must balance performance optimization over a range of on-design operating conditions with constraint satisfaction at off-design operating conditions. A multipoint optimization formulation can be used to represent on-design and off-design conditions with corresponding objective or constraint functions. Two methods are presented for obtaining optimal airfoil designs that satisfy all design objectives and constraints. The first method uses an unconstrained optimization algorithm where optimal design is achieved by minimizing a weighted sum of objective functions at each of the conditions. To address competing design objectives between on-design and off-design conditions, an automated procedure is used to weight off-design objective functions to limit their influence on the overall optimization. The second method uses the constrained optimization algorithm SNOPT, allowing aerodynamic constraints imposed at off-design conditions to be treated explicitly. Both methods are applied to the design of an airfoil for a hypothetical aircraft, which is formulated as an 18-point multipoint optimization.