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Aerodynamic shape optimization using the discrete adjoint of the Navier Stockes equations: Applications towards complex 3D configurations
- KATnet II Conference on Key Aerodynamic Technologies paper No.36 1, 12 14 May 2009, Bremen 21 tel-00925210, version 1
"... Within the next few years, numerical shape optimization based on high fidelity methods is likely to play a strategic role in future aircraft design. In this context, suitable tools have to be developed for solving aerodynamic shape optimization problems, and the adjoint approach- which allows fast a ..."
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Within the next few years, numerical shape optimization based on high fidelity methods is likely to play a strategic role in future aircraft design. In this context, suitable tools have to be developed for solving aerodynamic shape optimization problems, and the adjoint approach- which allows fast and accurate evaluations of the gradients with respect to the design parameters- is seen as a promising strategy. After describing the theory of the viscous discrete adjoint method and its implementation within the unstructured RANS solver TAU, this paper describes application for aerodynamic shape optimization. First wing and fuselage designs of the DLR-F6 wing-body aircraft are presented. A step forward in complexity is considered by applying the adjoint for flap and slat optimal settings of the DLR-F11 model, a wing-body aircraft in high-lift configuration. On all cases presented, optimization were successfully performed within a limited number of flows evaluations. 1
Adjoint Algorithm for CAD-Based Shape Optimization Using a Cartesian Method
"... We focus on the computation of objective function gradients using a discrete adjoint method for embedded-boundary Cartesian meshes. This is a significant step in our research toward using computer-aided design (CAD) directly for adjoint-based gradient computations. The approach treats the Cartesian ..."
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We focus on the computation of objective function gradients using a discrete adjoint method for embedded-boundary Cartesian meshes. This is a significant step in our research toward using computer-aided design (CAD) directly for adjoint-based gradient computations. The approach treats the Cartesian mesh as a rigid structure. Under this assumption, accurate evaluation of mesh sensitivities depends directly on the formulation within the layer of non-uniform cells, or cut-cells, immediately adjacent to the surface. The formulation is based on the linearization of a simple geometric constructor, which decouples the computation of shape sensitivities of the surface triangulation from the cut-cell sensitivities. As a result, the method is well suited to CAD-based optimization using parametric solid models. Detailed verification studies of gradient accuracy are presented for several two- and three-dimensional shape optimization problems. I.
Integrated Design of an Active Flow Control System Using a Time-Dependent Adjoint Method
"... Abstract. An exploratory study is performed to investigate the use of a time-dependent discrete adjoint methodology for design optimization of a high-lift wing configuration augmented with an active flow control system. The location and blowing parameters associated with a series of jet actuation or ..."
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Abstract. An exploratory study is performed to investigate the use of a time-dependent discrete adjoint methodology for design optimization of a high-lift wing configuration augmented with an active flow control system. The location and blowing parameters associated with a series of jet actuation orifices are used as design variables. In addition, a geometric parameterization scheme is developed to provide a compact set of design variables describing the wing shape. The scaling of the implementation is studied using several thousand processors and it is found that asynchronous file operations can greatly improve the overall performance of the approach in such massively parallel environments. Three design examples are presented which seek to maximize the mean value of the lift coefficient for the coupled system, and results demonstrate improvements as high as 27 % relative to the lift obtained with non-optimized actuation. This lift gain is more than three times the incremental lift provided by the non-optimized actuation.
ESDA2006-95557 FREEFORM DEFORMATION VS B-SPLINE REPRESENTATION IN INVERSE AIRFOIL DESIGN
"... ABSTRACT In this work FFD technique is compared to the classical parameterization technique using B-Spline curves by performing inverse airfoil design tests, with a Differential Evolution (DE) algorithm to serve as the optimizer. The criteria of the comparison between the two techniques are the ach ..."
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ABSTRACT In this work FFD technique is compared to the classical parameterization technique using B-Spline curves by performing inverse airfoil design tests, with a Differential Evolution (DE) algorithm to serve as the optimizer. The criteria of the comparison between the two techniques are the achieved accuracy in the approximation of the reference pressure distribution and the convergence behavior of the optimization algorithm. Experiments are presented, comparing FFD to BSpline techniques under the same flow conditions, for various numbers of design variables.
L N P
, 2010
"... nΩ nE nF nl nN np nLj t u v The generation of design parameter sensitivity derivatives is required for gradient-based optimization. Such sensitivity derivatives are elusive at best when working with geometry defined within the solid modeling context of Computer-Aided Design (CAD) systems. Solid mode ..."
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nΩ nE nF nl nN np nLj t u v The generation of design parameter sensitivity derivatives is required for gradient-based optimization. Such sensitivity derivatives are elusive at best when working with geometry defined within the solid modeling context of Computer-Aided Design (CAD) systems. Solid modeling CAD systems are often proprietary and always complex, thereby necessitating ad hoc procedures to infer parameter sensitivity. A new perspective is presented that makes direct use of the hierarchical associativity of CAD features to trace their evolution and thereby track design parameter sensitivity. In contrast to ad hoc methods, this method provides a more concise procedure following the model design intent and determining the sensitivity of CAD geometry directly to its respective defining parameters. Set of real numbers Set of features Set of edges Set of faces Set of loops Set of nodes Set of parameters Set of discretized vertices Edge position vector Node position vector Face position vector Number of features Number of edges Number of faces Number of faces/edges incident to node l Number of nodes Number of parameters Number of loops for face Fj Edge parameter Tensor product surface parameter
am Fachgebiet Simulation und Systemoptimierung
"... The choice of an adequate representation is an important part of every evolutionary design optimisation. A flexible representation which allows a huge number of design variation while getting along with a few parameters is preferable. In the past the Free-From Deformation method was successfully app ..."
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The choice of an adequate representation is an important part of every evolutionary design optimisation. A flexible representation which allows a huge number of design variation while getting along with a few parameters is preferable. In the past the Free-From Deformation method was successfully applied for design optimisation. In this diploma thesis an adaptive Free-Form Deformation is combined with an Evolu-tion Strategy. The aim is to automatically create a representation which is adapted to the problem and reduce the dependence on the initial representation build by a designer. Furthermore it should be analysed if such an adaptation can lead to a faster convergence. In a second part a direct manipulation technique is presented to increase the influ-ence of the object parameter on the design in order to speed up the optimisation. Both representations are tested at target matching problems. If the optimisation is applied to a fluid dynamics optimisation problem, a compu-tational grid is required to evaluate the designs. Since the Free-From Deformation represents deformations of an initial design, it can also be applied to a grid. Thus a costly re-meshing procedure can be omitted. To keep the structural composition of the mesh the deformations have to be restricted. The influence of these additional constraints is also analysed. Kurzfassung
FOR THE DEGREE OF
, 2014
"... Re-distributed by Stanford University under license with the author. This work is licensed under a Creative Commons Attribution-Noncommercial 3.0 United States License. ii I certify that I have read this dissertation and that, in my opinion, it is fully adequate ..."
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Re-distributed by Stanford University under license with the author. This work is licensed under a Creative Commons Attribution-Noncommercial 3.0 United States License. ii I certify that I have read this dissertation and that, in my opinion, it is fully adequate
Techniques for the Design of Active Flow Control Systems in Heavy Vehicles
"... This article focuses on the computational study of active flow control systems, such as Coanda jets, and the effects that these have on the drag and power consumption of heavy vehicles. To simulate the flow over the Ground Transportation System (GTS) model, which is a simplified geometrical model us ..."
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This article focuses on the computational study of active flow control systems, such as Coanda jets, and the effects that these have on the drag and power consumption of heavy vehicles. To simulate the flow over the Ground Transportation System (GTS) model, which is a simplified geometrical model used to represent heavy vehicles, the second order Unsteady Reynolds-Averaged-Navier-Stokes (URANS) equations were used. A top-view two-dimensional representation of the GTS model has been used to perform this study, and by adding Coanda jets to the trailing end, we aim to understand the aerodynamic effects of modifying the Coanda surface geometry, as well as the Coanda jet strength. Leveraging on the shape deformation capabilities integrated into SU2, an open source Computational Fluid Dynamics (CFD) suite, the shape of the Coanda surface has been controlled while the jet strength has been imposed by varying the plenum pressure. Computational simulations of the described geometry were used to generate a surrogate model of the power required by the vehicle. Finally, the surrogate model was used to visualize the design space, find trends, and understand the effect that the Coanda jets have on vehicle aerodynamics and energy consumption. I.
Adjoint assisted geometry design of a feedback controlled missile
"... Abstract: A novel optimisation framework using an adjoint cost sensitivity calculation, and integrating computer simulations of fluid dynamics, rigid body dynamics and control is proposed. A generic tail-fin steered missile under closed-loop control is used to show that the framework is able to gene ..."
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Abstract: A novel optimisation framework using an adjoint cost sensitivity calculation, and integrating computer simulations of fluid dynamics, rigid body dynamics and control is proposed. A generic tail-fin steered missile under closed-loop control is used to show that the framework is able to generate a detailed geometrical tail-fin design and tune control performance parameters that are directly related to the range and manoeuvrability of the missile. It is shown that this new methodology is able to reduce the aerodynamic drag by 2 % and the tracking error by about 3 % relative to the original design.
