1,721,226 research outputs found
Trajectory driven multidisciplinary design optimization of a sub-orbital spaceplane using non-stationary Gaussian process
Full text linkThis paper presents the multidisciplinary optimization of an aircraft carried sub-orbital spaceplane. The optimization process focused on three disciplines: the aerodynamics, the structure and the trajectory. The optimization of the spaceplane geometry was coupled with the optimization of its trajectory. The structural weight was estimated using empirical formulas. The trajectory was optimized using a pseudo-spectral approach with an automated mesh refinement that allowed for increasing the sparsity of the Jacobian of the constraints. The aerodynamics of the spaceplane was computed using an Euler code and the results were used to create a surrogate model based on a non-stationary Gaussian process procedure that was specially developed for this study.Aerodynamics, Wind Energy & PropulsionAerospace Engineerin
Adjoint quasi-three-dimensional aerodynamic solver for multi-fidelity wing aerodynamic shape optimization
No full textA quasi-three-dimensional method for wing aerodynamic analysis for drag prediction is presented. This method can predict the wing drag with a level of accuracy similar to higher fidelity three-dimensional CFD analysis, with a much lower computational cost. A tool has been developed based on the proposed method and the outputs of the tool have been validated using a higher fidelity CFD tool. Another advantage of the mentioned method (and the tool developed based on that) is to compute the derivatives of any function of interest, such as the wing drag, lift, or pitching moment, with respect to the design variables, mainly the wing geometry, using analytical methods. The tool uses a combination of the Adjoint method, the chain rule for differentiation, and the automatic differentiation to compute the sensitivities. The quasi-three-dimensional aerodynamic solver is used for a multi-fidelity wing aerodynamic shape optimization. A trust region algorithm is used to connect the low fidelity aerodynamic solver to a high fidelity CFD tool for wing drag prediction. The derivatives of the objective function are computed using the low fidelity solver, and the high fidelity solver is used to calibrate the results of the low fidelity one
Aerodynamic Shape Optimization Using Symbolic Sensitivity Analysis
No full textThe least-squares finite element method is used to solve the compressible Euler equations around airfoils in transonic regime. The symbolic analysis method is used to generate the element stiffness and force matrices. The equations of the element matrices are derived symbolically based on the flow primitive variables and the position of the element nodes. The symbolic analysis is also used to compute the exact derivatives of the residuals with respect to both design variables (e.g. the airfoil geometry) and the state variables (e.g. the flow velocity). The symbolic analysis allows to compute the exact Jacobian of the governing equations in a computationally efficient way, which is used for Newton iteration. Besides, using the symbolic analysis the sensitivities of the outputs, such as the airfoil drag, with respect to the design variables, such as the airfoil geometry, are computed using the discrete adjoint method without the need for automatic differentiation. This makes the analysis and optimization computationally more efficient
Vertically curved runways for reducing airport environmental impact and increasing aircraft productivity
No full textThis paper presents the concept and advantages of vertically curved runways for reducing the air pollution in the vicinity of airports, while also increasing the productivity of passenger aircraft. The shape of a curved runway was optimize to minimize the produced CO2 during an aircraft takeoff and to maximize the aircraft takeoff weight for a given runway horizontal length. A method for aircraft takeoff simulation is presented and validated using actual data of a passenger aircraft. Using that method, a series of single-objective as well as multi-objective optimizations was performed to find the optimum runway shape for different objectives: minimizing the produced CO2 during takeoff, maximizing the aircraft takeoff weight, and minimizing the runway construction cost, while achieving the first two objectives. The results of the optimizations showed that, for a Boeing 747-400 class aircraft, about 250 kg reduction in the produced CO2 during a takeoff can be achieved using a curved runway with the height of 60 m and the length of 3 km. On the other hand, the range of a similar aircraft can be increased by 2500 km using a curved runway with the same height and length comparing to a flat runway with the same horizontal length
Strategies for the grid stiffened composite panel topology optimization for minimum weight
No full textIn this paper, a topology optimization methodology for the minimum weight of the composite stiffened panel with the constraint on the criticial buckling load is presented. An existing finite element solver [1] for the analysis of the stiffened tow steered composite panels is extended to perform the topology optimization for the minimum weight. The panel and the stiffeners are modelled using 3 node traingular Classical Laminate Plate elements (CLPT) and 2 node timoshenko beam elements, respectively. To achieve the independent meshing of the plate and stringers, the Lagrange multiplier based on a weak formulation of the continuity requirements between the plate elements and the beam elements is used. For a specific critical buckling load, the optimum topology of the stiffeners in the stiffened composite panel depends not only on the stiffeners but also on the fiber patten of the composite panel. Therefore, design variables corrosponding to both fiber pattern in the skin and stiffeners needs to be considered. Manufacturing mesh approach presented in [1], is used to define the design variables corrosponding to the fiber pattern. The ground structure method is implemented to optimize stringers topology. The cross-sectional area of the stringers in the ground structure are defined as the design variables corrosponding to the stiffeners. To perform the robust the optimization, the analytical gradients of the buckling load and the weight of the stiffened panel with respect to design variables are implemented and verified using finite difference. The optimization for the minimum weight is performed for the varied complexities of the ground structures with the constraints on the critical buckling load
Multi-objective topology optimization of pin-fin heat exchangers using spectral and finite-element methods
No full textForced convective pin-fin heat exchangers, due to the high wet surface area per volume and the hindered thermal boundary layers, feature low thermal resistances. However, the considerable coolant pressure drop, particularly for densely packed fin arrays, imposes operational costs for pumping power supply. This paper develops a multi-objective topology optimization approach to optimize sink geometries in order to minimize thermal resistance and pressure loss, concurrently. In accordance to the pin-fin geometrical characteristics, a dedicated pseudo-3D conjugate heat transfer model is utilized, by assuming periodic flow and fin design pattern, to reasonably reduce the high cost of full-3D model optimization. For the solution of flow part, a pseudo-spectral scheme is used, which is intrinsically periodic and features a high spectral accuracy, and the finite element method for the non-periodic conjugate heat transfer model. Exact partial derivatives of the discrete solutions are obtained analytically by hand-differentiation. This task is rather convenient for the flow part, due to the simplicity of the pseudo-spectral implementation; however, the MATLAB symbolic toolbox is selectively utilized for the finite element code to ensure an error-free implementation. Finally, the sensitivities are computed directly or via a discrete adjoint method, for the flow and heat models, respectively. To examine the present approach, two approaches are used for optimization of a practical cooling task: constrained and unconstrained multi-objective formulations, where in all cases more emphasis is placed on thermal resistance minimization. A series of optimized heat sink geometries via constrained or unconstrained multi-objective optimizations are obtained to examine practical utility of the present approach. The optimized topologies demonstrated superior cooling performances at lower costs of pressure losses compared to conventional (circular) in-line and staggered fins, and confirmed the supremacy of topology over pure sizing optimization
Twin-fuselage configuration for improving fuel efficiency of passenger aircraft
No full textThe requirements of increasing air traffic volume while enhancing its sustainability for the next generation of air transportation demand a step change in aircraft performance, for which the development and technology escalation of ultra-high aspect ratio wings configurations is one key enabling strategy. However, compared with conventional aircraft, the ultra-high aspect ratio wings structure bears higher loads, which poses challenges to aircraft configuration design and related technologies. This paper describes the twin-fuselage (TF) concept as one of the promising configurations adopting ultra-high aspect ratio wings. A methodology of conceptual design and analysis framework for TF transport aircraft is developed by improving and integrating several methods and tools. A medium-range TF transport aircraft is designed, and a sensitivity analysis is carried out to explore the design space, and multidisciplinary design optimization is used to optimize the configuration of the TF transport aircraft. The results show a significant advantage of TF configuration over the conventional cantilever configuration, which presents reductions of 29.33% and 33.60% in the fuel consumption and maximum takeoff weight, respectively
Weight indexing for airfoil multi-objective optimization
No full textA new method for airfoil shape optimization is presented, in which the airfoil shape is optimized not only for the best aerodynamic efficiency but also for the minimum structural weight. To relate the structural weight to the airfoil shape a series of methods are prescribed for initial sizing of the wingbox structure. Based on these methods, a “weight index” is defined. The airfoil weight index is a mathematical equation that relates the structural weight of the wingbox to the airfoil shape. The structural weight of a wingbox reduces by increasing the weight index of the airfoil. A set of multi-objective optimizations is performed to find the Pareto front of the airfoil drag and the weight index
Coupled adjoint aerostructural wing optimization using quasi-three-dimensional aerodynamic analysis
No full textThis paper presents a method for wing aerostructural analysis and optimization, which needs much lower computational costs, while computes the wing drag and structural deformation with a level of accuracy comparable to the higher fidelity CFD and FEM tools. A quasi-threedimensional aerodynamic solver is developed and connected to a finite beam element model for wing aerostructural optimization. In a quasi-three-dimensional approach an inviscid incompressible vortex lattice method is coupled with a viscous compressible airfoil analysis code for drag prediction of a three dimensional wing. The accuracy of the proposed method for wing drag prediction is validated by comparing its results with the results of a higher fidelity CFD analysis. The wing structural deformation as well as the stress distribution in the wingbox structure is computed using a finite beam element model. The Newton method is used to solve the coupled system. The sensitivities of the outputs, for example the wing drag, with respect to the inputs, for example the wing geometry, is computed by a Ali Elham [email protected] Michel J. L. van Tooren [email protected] 1 Faculty of Aerospace Engineering, Delft University of Technology, Delft, Netherlands 2 McNair Center for Aerospace Research and Innovation, University of South Carolina, Columbia, South Carolina, USA combined use of the coupled adjoint method, automatic differentiation and the chain rule of differentiation. A gradient based optimization is performed using the proposed tool for minimizing the fuel weight of an A320 class aircraft. The optimization resulted in more than 10 % reduction in the aircraft fuel weight by optimizing the wing planfor
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