Showing papers in "AIAA Journal in 2017"
TL;DR: The intent of this document is to provide an introduction to modal analysis that is accessible to the larger fluid dynamics community and presents a brief overview of several of the well-established techniques.
Abstract: Simple aerodynamic configurations under even modest conditions can exhibit complex flows with a wide range of temporal and spatial features. It has become common practice in the analysis of these flows to look for and extract physically important features, or modes, as a first step in the analysis. This step typically starts with a modal decomposition of an experimental or numerical dataset of the flowfield, or of an operator relevant to the system. We describe herein some of the dominant techniques for accomplishing these modal decompositions and analyses that have seen a surge of activity in recent decades [1–8]. For a nonexpert, keeping track of recent developments can be daunting, and the intent of this document is to provide an introduction to modal analysis that is accessible to the larger fluid dynamics community. In particular, we present a brief overview of several of the well-established techniques and clearly lay the framework of these methods using familiar linear algebra. The modal analysis techniques covered in this paper include the proper orthogonal decomposition (POD), balanced proper orthogonal decomposition (balanced POD), dynamic mode decomposition (DMD), Koopman analysis, global linear stability analysis, and resolvent analysis.
1,110 citations
TL;DR: By incorporating data that can reveal the form of the innate model discrepancy, the applicability of data-driven turbulence models can be extended to more general flows.
Abstract: A modeling paradigm is developed to augment predictive models of turbulence by effectively using limited data generated from physical experiments. The key components of the current approach involve...
250 citations
TL;DR: This paper uses the concept of a dynamic Bayesian network to build a versatile probabilisitic network for airframe health monitoring.
Abstract: Current airframe health monitoring generally relies on deterministic physics models and ground inspections. This paper uses the concept of a dynamic Bayesian network to build a versatile probabilis...
243 citations
TL;DR: In this paper, experience gained from previous jet noise studies with the unstructured large-eddy simulation flow solver "Charles" is summarized and put to practice for the predictions of supersonic jets issued f...
Abstract: Experience gained from previous jet noise studies with the unstructured large-eddy simulation flow solver “Charles” is summarized and put to practice for the predictions of supersonic jets issued f...
207 citations
TL;DR: The National Jet Fuels Combustion Program led by the Federal Aviation Administration, the U.S. Air Force Research Laboratory, and the NASA as discussed by the authors was developed to develop combustion-related generic test and modeling capabilities that can improve the understanding of the impact of fuel chemical composition and physical properties on combustion, leading to accelerating the approval process of new alternative jet fuels.
Abstract: This paper provides an overview of the National Jet Fuels Combustion Program led by the Federal Aviation Administration, the U.S. Air Force Research Laboratory, and the NASA. The program follows from basic research from the U.S. Air Force Office of Scientific Research and results from the engine-company-led Combustion Rules and Tools program funded by the U.S. Air Force. The overall objective of this fuels program was to develop combustion-related generic test and modeling capabilities that can improve the understanding of the impact of fuel chemical composition and physical properties on combustion, leading to accelerating the approval process of new alternative jet fuels. In this paper, the motivation and objectives for the work, participating universities, gas-turbine-engine companies, other federal agencies, and international partners are described. This paper provides an in-depth discussion on the benefits to the fuels approval process, the rationale in selecting conventional and alternative fuels to...
188 citations
TL;DR: In this paper, the authors describe a numerical reproduction of the 22-in source diagnostic test fan rig of the NASA Glenn Research Center and perform numerical flow simulations for three different rotor configurations.
Abstract: The present work describes a numerical reproduction of the 22-in source diagnostic test fan rig of the NASA Glenn Research Center. Numerical flow simulations are performed for three different rotor...
123 citations
TL;DR: A novel formulation of gradient-enhanced surrogate model, called weighted gradient- enhanced kriging, is proposed and used in combination with the cheap gradients obtained by the adjoint method to a surrogate model.
Abstract: A novel formulation of gradient-enhanced surrogate model, called weighted gradient-enhanced kriging, is proposed and used in combination with the cheap gradients obtained by the adjoint method to a...
112 citations
TL;DR: A comprehensive review of aerofoil shape parameterization methods that can be used for aerodynamic shape optimization is presented in this paper, where seven parameterisation methods are considered for a range of desi...
Abstract: A comprehensive review of aerofoil shape parameterization methods that can be used for aerodynamic shape optimization is presented. Seven parameterization methods are considered for a range of desi...
111 citations
TL;DR: Generating realistic turbulent inflow conditions for large-eddy simulations and other large-scale resolving approaches is essential to fully exploit the ever-increasing capabilities of modern compu... as mentioned in this paper.
Abstract: Generating realistic turbulent inflow conditions for large-eddy simulations and other large-scale-resolving approaches is essential to fully exploit the ever-increasing capabilities of modern compu...
98 citations
TL;DR: In this article, the authors proposed an approach to solve the NICOP problem in the context of artificial neural networks, which was supported by the U.S. Office of Naval Research (NICOP).
Abstract: Office of Naval Research (Grant IDs: N00014-13-1-0244, N00014-14-1-0242, N62909-12-1-7116 (NICOP)), College of Engineering at Virginia Tech, AVEC Incorporated
93 citations
TL;DR: High-fidelity computational modeling and optimization of aircraft configurations have the potential to enable engineers to create more efficient designs that require fewer unforeseen modifications.
Abstract: High-fidelity computational modeling and optimization of aircraft configurations have the potential to enable engineers to create more efficient designs that require fewer unforeseen modifications ...
TL;DR: In this article, the authors present the experimental assessment of the aerodynamic benefit of boundary layer ingestion for an advanced design civil transport aircraft, the D8 "double bubble", carried out from 2010 to 2013.
Abstract: This paper presents the experimental assessment of the aerodynamic benefit of boundary layer ingestion for an advanced design civil transport aircraft, the D8 “double bubble,” carried out from 2010...
TL;DR: In this paper, uncertainty quantification of turbulence model closure coefficients is performed for transonic flow over an axisymmetric bump and the RAE 2822 transonic airfoil.
Abstract: The goal of this work is to quantify the uncertainty and sensitivity of commonly used turbulence models in Reynolds-averaged Navier–Stokes codes due to uncertainty in the values of closure coefficients for transonic wall-bounded flows and to rank the contribution of each coefficient to uncertainty in various output flow quantities of interest. Specifically, uncertainty quantification of turbulence model closure coefficients is performed for transonic flow over an axisymmetric bump and the RAE 2822 transonic airfoil. Three turbulence models are considered: the Spalart–Allmaras model, Wilcox (2006) k-ω model, and Menter shear-stress transport model. The FUN3D code developed by NASA Langley Research Center is used as the flow solver. The uncertainty quantification analysis employs stochastic expansions based on non-intrusive polynomial chaos for efficient uncertainty propagation. Several integrated and point quantities are considered as uncertain outputs for both computational fluid dynamics problems. Closur...
TL;DR: In this article, the various separation control mechanisms of burstmode actuation with a dielectric barrier discharge plasma actuator were experimentally investigated and the control of the separated fl...
Abstract: The various separation control mechanisms of burst-mode actuation with a dielectric barrier discharge plasma actuator were experimentally investigated in this study. The control of the separated fl...
TL;DR: The Hyperloop vehicle is a conceptual mode of transportation in which a pod travels at high speed through a low-pressure tunnel to minimize the aerodynamic drag as discussed by the authors, which is similar to our approach.
Abstract: The Hyperloop vehicle is a conceptual mode of transportation in which a pod travels at high speed through a low-pressure tunnel to minimize the aerodynamic drag. In the current paper, an aerodynami...
TL;DR: In this article, the potential wing weight savings of a full-size aeroelastically tailored wing are assessed by optimizing the properties of a three-dimensional finite element model using straight-fiber and tow-steered composites in the skins.
Abstract: There has been an increasing effort to improve aircraft performance through using composite tailored structures, not only to reduce weight, but to exploit beneficial aeroelastic couplings. Recent work has considered the ability to tow steer the composite plies to achieve better performance. Here, the potential wing weight savings of a full-size aeroelastically tailored wing are assessed by optimizing the properties of a three-dimensional finite element model using straight-fiber and tow-steered composites in the skins. One- and two-dimensional thickness and laminate rotation angle variations are considered as design freedoms. The jig shape is updated to maintain a fixed 1g flight shape, and optimization constraints are implemented on the strains and buckling loads due to maneuver and dynamic gust loads, flutter stability, and control effectiveness for different flight conditions. The optimal main fiber direction is rotated forward of the front spar direction in the outer wing, leading to extension-shear c...
TL;DR: In this paper, the origins and subsequent development of the Jameson-Schmidt-Turkel scheme were discussed, and a description of the historical background of the scheme was given.
Abstract: This paper is in response to an invitation to give a presentation on the origins and subsequent development of the Jameson–Schmidt–Turkel scheme. After a description of the historical background an...
TL;DR: In this article, an improved immersed boundary method for turbulent flow simulation on Cartesian grids is proposed to determine the appropriate boundary conditions, near-wall approximation of the mean-flow equatio...
Abstract: An improved immersed boundary method for turbulent flow simulation on Cartesian grids is proposed. To determine the appropriate boundary conditions, near-wall approximation of the mean-flow equatio...
TL;DR: In this paper, the transonic flow over a half wing-body configuration representative of a large civil aircraft was analyzed and the presence of shock-wave oscillations inducing unsteady loads that can cause serious damage to the aircraft.
Abstract: This paper presents a numerical study of the transonic flow over a half wing–body configuration representative of a large civil aircraft. The Mach number is close to cruise conditions, whereas the high angle of attack causes strong separation on the suction side of the wing. Results indicate the presence of shock-wave oscillations inducing unsteady loads that can cause serious damage to the aircraft. Transonic shock buffet is found. Based on exploratory simulations using a baseline grid, the region relevant to the phenomenon is identified and mesh adaptation is applied to significantly refine the grid locally. Time-accurate Reynolds-averaged Navier–Stokes and delayed detached–eddy simulations are then performed on the adapted grid. Both types of simulation reproduce the unsteady flow physics, and much information can be extracted from the results when investigating frequency content, the location of unsteadiness, and its amplitude. Differences and similarities in the computational results are discussed in...
TL;DR: In this paper, the authors used the measured pitot pressure fluctuations and correlations for the receptivity coefficient to estimate the initial amplitudes of the second mode in hypersonic wind tunnels.
Abstract: This paper presents new methodologies based on Mack’s amplitude method to estimate the start of transition in hypersonic wind tunnels when the second mode dominates the transition process. The methodologies rely on linear stability computations, measured or modeled tunnel noise, and experimentally determined second-mode breakdown amplitude and receptivity correlations. The first technique uses the measured pitot pressure fluctuations and correlations for the receptivity coefficient to estimate the initial amplitudes. The second technique replaces pitot pressure measurements with a freestream noise spectral amplitude model based on the parameters found in Pate’s correlation. The rationale behind this new model and new insight into Pate’s correlation are provided. The methods can successfully correlate Tunnel 9 and Tunnel F cone measurements at Mach numbers between 9 and 10, unit Reynolds numbers between 1.8 and 30 million per meter, and nose-tip radii between 1.5 and 12.7 mm. The standard error between the...
TL;DR: In this paper, a comprehensive experimental study has been performed for symmetric NACA 0012 and cambered NACA 65(12)-10 airfoils with a variety of trailing-edge serrations over a wide range of angles of attack.
Abstract: A comprehensive experimental study has been performed for symmetric NACA 0012 and cambered NACA 65(12)-10 airfoils with a variety of trailing-edge serrations over a wide range of angles of attack. ...
TL;DR: The performance of two wall models based on Reynolds-averaged Navier-Stokes is compared in large-eddy simulation of a high Reynolds number separating and reattaching flow over the NASA wall-mounted hump to improve flow prediction on a coarse grid.
Abstract: The performance of two wall models based on Reynolds-averaged Navier-Stokes is compared in large-eddy simulation of a high Reynolds number separating and reattaching flow over the NASA wall-mounted hump. Wall modeling significantly improves flow prediction on a coarse grid where the large-eddy simulation with the no-slip wall boundary condition fails. Low-order statistics from the wall-modeled large-eddy simulation are in good agreement with the experiment. Wall-pressure fluctuations from the resolved-scale solution are in good agreement with the experiment, whereas wall shear-stress fluctuations modeled entirely through the wall models appear to be significantly underpredicted. Although the two wall models produce comparable results in the upstream attached flow region, the nonequilibrium wall model outperforms the equilibrium wall model in the separation bubble and recovery region where the key assumptions in the equilibrium model are shown to be invalid.
TL;DR: In this article, the electrohydrodynamic thrust generated by wire-cylinder electrodes under high dc voltage is experimentally analyzed, for which the experimental observations are presented in terms of electric field and thrust density.
Abstract: The electrohydrodynamic thrust generated by wire–cylinder electrodes under high dc voltage is experimentally analyzed. Some recent experimental studies have shown that electrohydrodynamic thrusters produced by corona discharge and ionic wind are able to deliver high thrust-to-power ratio, which reopens prospects for electrohydrodynamic propulsion. From simple considerations based on ultralight aircraft mass, aerodynamics, battery mass, and experimental electrohydrodynamic thrust densities, their potential for applications is showcased. Furthermore, an experimental study is performed, for which the experimental observations are presented in terms of electric field and thrust density. This allows a simplified and synthetic presentation of propulsive properties. Various experimental biases have been identified and corrected. The measure of time-periodic oscillations of the airflow in the back of the thruster pinpoints a possible wake effect due to the impact of ionic wind on electrodes. The variations of the associated drag are studied when varying the position of the collecting electrodes. It is shown that aerodynamic losses can be significant in experimental electrohydrodynamic thrusters.
TL;DR: In this paper, an oxidation model for carbon surfaces has been developed where the gas surface reaction mechanisms and corresponding rate parameters are based solely on observations from recent molecular beam expander observations.
Abstract: An oxidation model for carbon surfaces has been developed where the gas–surface reaction mechanisms and corresponding rate parameters are based solely on observations from recent molecular beam exp...
TL;DR: In this article, the authors investigated flow separation control on an adverse pressure gradient ramp model using various flow-control methods in the NASA Langley Research Center's 15-in. wind tunnel.
Abstract: Flow-separation control on an adverse-pressure-gradient ramp model was investigated using various flow-control methods in the NASA Langley Research Center’s 15 in. wind tunnel. Sweeping jet actuato...
TL;DR: In this paper, direct numerical simulation is performed on a 38.1% scale Hypersonic International Flight Research Experimentation Program Flight 5 forebody to study stationary crossflow instability.
Abstract: Direct numerical simulation is performed on a 38.1% scale Hypersonic International Flight Research Experimentation Program Flight 5 forebody to study stationary crossflow instability. Computations ...
TL;DR: In this article, the Intelligent Design Methodologies for Low Pollutant Combustors for Aero-Engines (IDMC) project was used for low-pollutant combustion.
Abstract: The research leading to these results received funding from the European Community’s Seventh Framework Programme (FP7/2007- 2013)under grant agreement no.265586 and was conducted within the Intelligent Design Methodologies for Low Pollutant Combustors for Aero-Engines project.
TL;DR: In this paper, a novel approach was developed by leveraging the significant discrepancies in attenuation characteristics of ultrasonic waves traveling in different ice types (i.e., rime or glaze).
Abstract: A novel approach, which is capable of characterizing different types of ice accretion, was developed by leveraging the significant discrepancies in attenuation characteristics of ultrasonic waves traveling in different ice types (i.e., rime or glaze). While the theories of acoustic attenuation in pulse-echo configuration for a multilayer structure were formulated, a feasibility study was also performed to demonstrate the ultrasonic-attenuation-based technique to characterize two different types of ice samples representative of typical rime and glaze ice accretion seen over airframe surfaces. Significant differences were found in the ultrasonic attenuation characteristics between the two compared ice samples over the frequency range of 5–15 MHz. The attenuation coefficients of the rime-like ice sample were found to be much greater than those of the glaze-like ice sample at any given ultrasonic frequencies. While the values of ultrasonic attenuation coefficients would increase with ultrasonic frequency for ...