1,720,974 research outputs found
Multi-Fidelity Design of Aeroelastic Wing Tip Devices
No full textIn recent years, significant resources have been invested to further improve the efficiency and environmental sustainability of modern aircraft. A possible strategy consists of reducing the induced-drag contribution (40% of total drag) by means of wing tip devices, e.g. winglets. However, these solutions have a negative impact on structural sizing, requiring reinforcements, and aeroelastic stability, requiring mass balancing. The subject of this study is the numerical study of an alternative wing tip device. In particular, two different design concepts are presented, namely discrete and raked options. These solutions improve the aerodynamic efficiency by extending the wing span and feature an integrated aeroelastic passive load alleviation capability. The design of the wing tip devices follows a multi-fidelity approach, closely matching today's best practices in the aerospace industry. In the first part of the study, the design phase is carried out with low-fidelity very efficient tools. In the second part, the most promising solutions are verified with high-fidelity more expensive tools, within the framework of computational aeroelasticity
Multi-Fidelity Framework for the Design and MSD/CFD Verification of Flutter Suppression Active Control System
No full textAircrafts are complex machines in which the overall performances are determined by the cooperation of several subsystems. For the design of modern aircraft, interaction between aerodynamics, structural dynamics, flight dynamics and active controls, is nowadays becoming more and more important, mainly due to the increasing dimensions, the weight savings, and the high flexibility of structures. Thus, subsystems frequencies are very close to each other, and coupled multidisciplinary co-simulations are needed to predict the air-craft performances, even in the preliminary design phase. In this work, a high-fidelity free software co-simulation environment is proposed to simulate coupled aerodynamics and structural dynamics problems. Such a platform is used to verify the performances of an active control system for flutter suppression designed by means of low-fidelity efficient tools
Grid convergence assessment for adaptive grid simulations of normal drop impacts onto liquid films in axi-symmetric and three-dimensional geometries
Get PDFNormal liquid drop impact on a liquid film is studied numerically using a modified OpenFOAM solver in three-spatial dimensions, in which dynamic grid refinement is modified to accurately describe the initial conditions before impact. Numerical simulations are found to accurately predict the evolution of the splashing lamella. A new procedure for assessing grid convergence is introduced, which is based on the definition of a hierarchical set of bounding boxes in which the total liquid volume is computed to assess global as well as local grid convergence
Comparison of Acceleration Techniques on CFD Open-Source Software for Aerospace Applications
No full textComputational Fluid Dynamics (CFD) is a fundamental tool for the analysis and optimization of aerodynamic designs for internal and external ows. Alongside with the research of formulations that can accurately predict experimental data, a fundamental goal is also represented by solvers computational e ciency. In this paper a GPU-accelerated density-based and a coupled ressure-based solvers are proposed as two possible solutions to accelerate the simulation of compressible viscous ows. The first strategy is supported by the nowadays GPUs single precision performances, reaching computational power of the order of TFLOPS at few hundreds of USD and providing high performance/Watt ratios. However they require speci cally designed algorithms and programming languages. The one adopted in this work is based on OpenCL.The second strategy has instead the aim to resolve the usual convergence deterioration of the SIMPLE family algorithms improving the variables coupling. In this work an introduction of the fundamental details of the two formulations and solver architectures is provided. A validation campaign using experimental measurements is then presented for the most important applications in propulsion, external aerodynamics and supersonic flows
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Implementation of Explicit Density-Based Unstructured CFD Solver for Turbomachinery Applications on Graphical Processing Units
No full textFor the aerodynamic design of multistage compressors and turbines Computational Fluid Dynamics (CFD) plays a fundamental role. In fact it allows the characterization of the complex behaviour of turbomachinery components with high fidelity. Together with the availability of more and more powerful computing resources, current trends pursue the adoption of such high-fidelity tools and state-of-the-art technology even in the preliminary design phases. Within such a framework Graphical Processing Units (GPUS) yield further growth potential, allowing a significant reduction of CFD process turn-around times at relatively low costs. The target of the present work is to illustrate the design and implementation of an explicit density-based RANS coupled solver for the efficient and accurate numerical simulation of multi-dimensional time-dependent compressible fluid flows on polyhedral unstructured meshes. The solver has been developed within the object-oriented OpenFOAM framework, using OpenCL bindings to interface CPU and GPU and using MPI to interface multiple GPUS. The overall structure of the code, the numerical strategies adopted and the algorithms implemented are specifically designed in order to best exploit the huge computational peak power offered by modern GPUS, by minimizing memory transfers between CPUs and GPUS and potential branch divergence occurrences. This has a significant impact in terms of the speedup factor and is especially challenging within a polyhedral unstructured mesh framework. Specific tools for turbomachinery applications, such as Arbitrary Mesh Interface (AMI) and mixingplane (MP), are implemented within the GPU context. The credibility of the proposed CFD solver is assessed by tackling a number of benchmark test problems, including Rotor 67 axial compressor, C3X stator blade with conjugate heat transfer and Aachen multi-stage turbine. An average GPU speedup factor of approximately S ≈ 50 with respect to CPU is achieved (single precision, both GPU and CPU in 100 USD price range). Preliminary parallel scalability test run on multiple GPUS show a parallel efficiency factor of approximately E ≈ 75%
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