1,720,968 research outputs found
Enhancing Accuracy in Mixed-Element Grids and Convergence on Skewed Grids for the Two-Dimensional Edge-Based Compressible Navier-Stokes Solver
No full textIn this paper, we apply a recently proposed flux correction for finite-volume discretizations to an edge-based compressible Navier-Stokes solver. Through numerical experiments, we demonstrate that applying this correction solely to the inviscid terms of the equations results in second-order convergence of the discretization error, without any modification of the viscous terms. Second-order accuracy is achieved on arbitrary mixed-element grids and for a wide range of Reynolds numbers including both convection- and viscous-dominated flows. Second-order accuracy is preserved also for an arbitrary centroid definition, which is known to destroy secondorder accuracy of the edge-based solver, and the face-area-weighted centroid can result in faster time-to-solution for skewed triangular grids. Results show that the proposed scheme yields a truly grid transparent discretization that can be used to enhance accuracy on mixed-element grids and accelerate convergence on stretched triangular meshes
Towards a Two-Stage Multi-Fidelity Shape Optimization Approach to Noise Reduction in Urban Air Mobility Applications
No full textWe propose a two-stage optimization framework based on computational models of different fidelity. The framework integrates two sequential stages. Namely, an exploratory stage, based on a Bayesian approach, followed by the exploitative stage, executed using gradient-based method. First, the optimizer employs aerodynamic solvers of increasing fidelity to explore the entire design space and identify promising design candidates. After, the geometry is reparametrized and the design space expanded. An adjoint-based optimizer refines the design using a high fidelity model. Overall, the goal is to reduce the noise produced by an isolated propeller tailored to Urban Air Mobility applications. The objective is to automatically design a two-blade propeller, minimizing the tonal noise signature, evaluated using the hybrid Ffowcs Williams-Hawkings method, while meeting specific aerodynamic performance targets. The proposed optimization architecture surpasses standalone Bayesian and adjoint methods in designing a high-thrust propeller with reduced tonal noise emissions during forward flight, highlighting the potential benefits of incorporating a positively swept and dihedral tip region
Automatic Shape Optimization of a Non-Planar Wing Based on Discrete Adjoint and Radial Basis Function Mesh Deformation
Full text linkTowards an open-source framework for Fluid–Structure Interaction using SU2, MBDyn and preCICE
Full text linkFluid-Structure Interaction (FSI) problems are a primary concern for the aerospace industry. Predicting the deformation of flexible structures due to aerodynamic forces is essential in different scenarios, e.g., for determining the performance of rotorcrafts and wind turbines. In this context, we present a new high-fidelity, open-source, modular, and user-friendly FSI simulation framework by coupling the well-established fluid solver SU2 with the multi-body structural solver MBDyn. The SU2 suite solves steady and unsteady Euler and RANS equations using a finite volume method on unstructured grids. The aerodynamic loads on the surfaces are then passed to MBDyn. Through a multi-body analysis, rotations, displacements, and the structural response of rotorcraft systems are efficiently computed and exchanged back with the fluid solver. A partitioned approach is used between the two codes, each specific for a single physical domain. Both explicit and implicit coupling were considered. The coupling is obtained through the library preCICE, which treats the two specialized solvers as "black boxes"and provides data mapping between non-matching grids. Classical FSI test cases are presented and results are compared with data from literature to validate the framework
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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