G11
Optimisation 2

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10:40
conference time (CEST, Berlin)
Recent Developments for Non-parametric Non-linear Sizing, Shape and Bead Optimization
27/10/2021 10:40 conference time (CEST, Berlin)
Room: G
C. Pedersen, S. Mulmule (Dassault Systemes, DEU); C. B.W. Pedersen (Kingshuk Bose, USA); R. Fan (Yale University, USA)
C. Pedersen, S. Mulmule (Dassault Systemes, DEU); C. B.W. Pedersen (Kingshuk Bose, USA); R. Fan (Yale University, USA)
The present work shows the latest static structural non-linear non-parametric sizing, shape and bead optimization developments allowing industrial engineers to take advantage of innovative design opportunities permitted by applying non-linear realistic simulation for optimization. A commercially available non-parametric structural optimization program (Tosca) which automatically modifies the finite element input deck (Abaqus) in each optimization iteration, drives the optimization workflow. The present structural optimization disciplines are sizing of the sheet structures where the shell thicknesses are design variables as well as shape and bead optimization where the nodal positions of the finite elements are the design variables allowing non-parametric shape and bead optimization, respectively. To the best of our knowledge, this is the first work that shows results for non-linear sizing, shape and bead optimization using adjoint sensitivities of static CAE models including simultaneously the three modeling non-linearities as large deformations, plasticity as material non-linearity and contact. An application of sizing optimization is for a bumper model consisting of shell elements where each of the shell thicknesses represents one design variable. The contact between the bumper and a rigid component is included. The constitutive material modeling is elastoplastic as well as large deformation is also included. The present objective is to minimize the mass of the structure subject to static energy absorption requirements. Additionally, the same non-linear sizing optimization concept will be shown for a static side impact of a full car model and non-linear collapse of a jacket structure. Frequently, the design aim for non-parametric shape and bead optimization is to minimize or to constrain the plastic deformation of misuse load cases. Here automotive applications are shown where the geometrical non-linearities are also included for realistic model the bending forces and membrane force being principle for yielding correct optimized designs for the plastic deformation. - - - - - -
Abaqus, Tosca, structural optimization, non-linear optimization using adjoint sensitivities
11:00
conference time (CEST, Berlin)
Game Theory Based Methodologies For Optimization of Interwoven Systems
27/10/2021 11:00 conference time (CEST, Berlin)
Room: G
L. Battaglia, A. Clarich (Esteco SPA, ITA)
L. Battaglia, A. Clarich (Esteco SPA, ITA)
Multi-disciplinary Design Optimization (MDO) problems are widely present in industrial design practice and in the Aerospace industry, where the performances coming from the simulation of multiple disciplines have to be optimized simultaneously. Specifically in the preliminary concept design, a typical scenario for the MDO problems is represented by interwoven systems, for which some variables are simultaneously input and output parameters of different disciplines. To solve these problems, many approaches exist in literature, most of them based on the application of gradient-based optimization algorithms with the evaluation of multiple loops to get an equilibrium solution for each design. A possible limitation of this approach is generally related to the large computational cost required to obtain the equilibrium point for each design. In addition, not every input variable combination allows to get an equilibrium point, causing convergence problems to the algorithms. In this paper we propose a different methodology, based on the application of Game Theory strategies, to solve these problems by a reduced number of discipline evaluations. The idea is to decouple the main objective(s) of the optimization problem from the one related to the reach of an equilibrium point of the system. In one version of the methodology, following the definition of a Hierarchical Strategy Game, the leader player optimizes the main objectives of the problem, while the follower player is in charge of the equilibrium point objective, which is optimized for every design proposed by the leader. In the second version of the methodology, following the definition of a Competitive Strategy Game, the two objectives are solved simultaneously by two players, who act following their own criteria and exchanging information at each step. The methodology is applied to a conceptual supersonic aircraft design MDO problem, using numerical models developed in the framework of the European Project HISAC [https://cordis.europa.eu/project/id/516132]. The advantage in terms of results and computational effort, compared to a classic methodology based on equilibrium-loops, is proven in the paper.
MDO optimization; interwoven systems
11:20
conference time (CEST, Berlin)
Aerodynamic Efficiency Potentials of a Tricar Stern Derived From an Ordinary Car Based on Open Source CFD-, Morphing - and Optimization Software
27/10/2021 11:20 conference time (CEST, Berlin)
Room: G
P. Stang, S. Staus, K. Timmann (Ostfalia University of Applied Sciences, DEU)
P. Stang, S. Staus, K. Timmann (Ostfalia University of Applied Sciences, DEU)
Sustainability and efficiency drive vehicle development and are becoming an increasingly important selling point. Throughout this paper, an ordinary sedan car body is modified using a single rear wheel to form a tricar. Therefore, we examine potentials for aerodynamic drag reduction of the DrivAer’s bodywork. Morphing of the geometry takes place behind the B-pillar. Drag coefficients are obtained through stationary CFD calculations utilizing a realizable k-epsilon-turbulence model in OpenFOAM®. Employing genetic optimization and the efficient global optimization (EGO) algorithm of the Dakota optimization software, a low drag/negative lift objective function leads to a set of shape parameters defining the car’s stern in Blender®. Either a B-spline control net, section cuts or proportional editing are used as shape design tools with different amounts of parameters in a set. The lattice modifier of Blender® uses B-splines to interpolate the deformations from a control net on to the geometry surface. A further method is based on (multiple) vertical cuts along the x-axis which are translated and scaled. A smooth transition between those cuts is achieved through Blender®’s bevel modifier and a relative offset width. With the method of proportional editing in Blender®, there is just one vertical cut at the far end of the car. This cut can be scaled and translated while proportional editing adapts the geometry in the defined influence area to create a smooth transition. Results reveal that the stern is becoming extremely small and, therefore, a big proportion of the rear tyre is uncovered causing turbulences. A second optimization via a wing shaped wheel fairing is constructed and parametrized to solve this issue. Efficiency potentials are quantified though the WLTP-Cycle calculations applying the achieved drag coefficients. Finally, we demonstrate that the drag is reduced by more than 25% and the energy demand can be reduced by up to 22%.
car aerodynamics, shape optimization, morphing, open source, CFD, OpenFOAM, Dakota, Blender, realizable k-epsilon, efficient global optimization (EGO), drag coeffcient, lift coefficient, WLTP, DrivAer
11:40
conference time (CEST, Berlin)
Combining Parametric and Non-Parametric Structural Optimization for Urban Air Mobility Conceptual Development
27/10/2021 11:40 conference time (CEST, Berlin)
Room: G
T. Moecker (Dassault Systemes Deutschland GmbH, DEU); V. Savane (Dassault Systemes, IND); R. Keswani (Dassault Systemes, FRA); R. Fu (Dassault Systemes, USA)
T. Moecker (Dassault Systemes Deutschland GmbH, DEU); V. Savane (Dassault Systemes, IND); R. Keswani (Dassault Systemes, FRA); R. Fu (Dassault Systemes, USA)
With multiple startups and Original Equipment Manufacturers (OEMs) competing to develop conceptual vehicles for Urban Air Mobility (UAM), new tools and methods are necessary to streamline the design process to meet the ambitious goals of this emerging industry. Determining appropriate lightweight configurations for the airframe structure is a challenging task, as it requires close collaboration between different disciplines, such as design, structural optimization and flight mechanics. The focus of this paper is on proposing an efficient workflow for conceptual structural sizing, which benefits from the tight integration of parametric design, simulation and optimization capabilities. To obtain the optimized lightweight design, parametric and non-parametric optimization techniques are combined. The workflow is entirely based on parametric design data, generated through a combination of graphical visual scripting and interactive 3D modeling. This method enables the engineer to create logic to parametrically build all required components of the internal structure, including ribs, spars, frames, and stringers. Fully associated with this parametric design model, a structural model of the UAM vehicle is built, allowing for design space exploration. In any given flight condition, the vehicle is subjected to aerodynamic loads, rotor forces, gravity and inertia loads. Aerodynamic loads are determined using a Computational Fluid Dynamics model, which is again fully associated with design, while rotor forces are computed to ensure flight loads equilibrium. Considering two exemplary load cases representing critical flight conditions, parametric and non-parametric structural optimization techniques are then combined, aiming at minimal weight for a targeted stress level. Based on results from a parametric design study, an optimized configuration of the parametric UAM vehicle is determined. In addition, non-parametric sizing techniques are applied, allowing for further reduction of mass by optimizing the distribution of skin thicknesses and stiffener properties. In a final step, structural requirement checks for buckling and strength are performed to validate the optimized configuration.
Structural Optimization, Conceptual Design, Urban Air Mobility, Lightweight Design, Airframe Structure
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