Showing papers in "AIAA Journal in 2018"
TL;DR: Since its introduction, the NASA Common Research Model has proved a useful aerodynamic benchmark for predicting computational-fluid-dynamics-based drag and aerodynamic design optimization.
Abstract: Since its introduction, the NASA Common Research Model has proved a useful aerodynamic benchmark for predicting computational-fluid-dynamics-based drag and aerodynamic design optimization. The mode...
107 citations
TL;DR: A direct numerical simulation database of high-speed zero-pressure-gradient turbulent boundary layers developing spatially over a flat plate with nominal freestream Mach number ranging from 2.5 to 14 and wall-to-recovery temperature ranging from 0.18 to 1.0 is presented.
Abstract: In this paper, we present a direct numerical simulation database of high-speed zero-pressure-gradient turbulent boundary layers developing spatially over a flat plate with nominal freestream Mach number ranging from 2.5 to 14 and wall-to-recovery temperature ranging from 0.18 to 1.0. The flow conditions of the DNS are representative of the operational conditions of the Purdue Mach 6 quiet tunnel, the Sandia Hypersonic Wind Tunnel at Mach 8, and the AEDC Hypervelocity Tunnel No. 9 at Mach 14. The DNS database is used to gauge the performance of compressibility transformations, including the classical Morkovin's scaling and strong Reynolds analogy as well as the newly proposed mean velocity and temperature scalings that explicitly account for wall heat flux. Several insights into the effect of direct compressibility are gained by inspecting the thermodynamic fluctuations and the Reynolds stress budget terms. Precomputed flow statistics, including Reynolds stresses and their budgets, will be available at the website of the NASA Langley Turbulence Modeling Resource, allowing other investigators to query any property of interest.
106 citations
TL;DR: In this paper, a 50-year journey through flow control strategies that seek to achieve viscous drag reduction in turbulent boundary layers is presented, focusing on different mechanisms underlying flow control.
Abstract: A 50 year journey through flow control strategies that seek to achieve viscous drag reduction in turbulent boundary layers is presented. These are shown to focus on different mechanisms underlying ...
100 citations
TL;DR: In this article, the onset of unsteady separation and dynamic stall vortex formation over a constant-rate pitching airfoil is analyzed by means of high-fidelity large-eddy simulations.
Abstract: The onset of unsteady separation and dynamic stall vortex formation over a constant-rate pitching airfoil is analyzed by means of high-fidelity large-eddy simulations. The flowfields are computed b...
94 citations
TL;DR: In this paper, a first principles understanding of the sound field produced by multi-rotor drones in hover is presented, with configurations ranging from 8 to 12-in. diameters.
Abstract: A first principles understanding of the sound field produced by multirotor drones in hover is presented. Propeller diameters ranging from 8 to 12 in. are examined and with configurations comprising...
90 citations
TL;DR: In this article, a wall-modeled large-eddy simulation of transonic buffet phenomena over the OAT15A supercritical airfoil at two different Mach number conditions (nonbuffet M∞=0.715 and buffet M ∼ 0.73) is presented.
Abstract: In this study, wall-modeled large-eddy simulation of transonic buffet phenomena over the OAT15A supercritical airfoil at two different Mach number conditions (nonbuffet M∞=0.715 and buffet M∞=0.73 ...
75 citations
TL;DR: In this paper, a new empirical model for turbulent boundary-layer wall pressure spectrum was presented and validated against measurement data for zero pressure gradient flat plate flows and adaption of flat plate flow.
Abstract: This paper presents a new empirical model for turbulent boundary-layer wall pressure spectrum and validates the new model against measurement data for zero pressure gradient flat plate flows and ad...
75 citations
TL;DR: In this paper, the applicability of actuator-disk and actuator line models to reduce the cost of propeller modeling is investigated in its most accurate form, by extracting and applying propeller blade loading from full-blade simulations.
Abstract: This paper examines the capability of a commercial RANS solver for the simulation of wingtip-mounted propellers. The applicability of actuator-disk and actuator-line models to reduce the cost of propeller modeling is investigated in its most accurate form, by extracting and applying propeller blade loading from full-blade simulations. The results obtained from all numerical simulations are validated based on measurement data from an in-house wind-tunnel experiment. An extensive grid dependency study is presented for the isolated propeller and the wing to distinguish discretization errors from model errors. It is concluded that RANS CFD with a simple one-equation turbulence model (Spalart–Allmaras) is capable of modeling the aerodynamic interactions for the wingtip-mounted propeller in tractor configuration, provided that numerical diffusion is accounted for by a grid dependency study or prevented by local grid refinement. The actuator-line model is fully able to replace propeller blade modeling in the simulation, and agreement with the full-blade simulations is found in time-accurate and time-average wing loading. The actuator-disk model further reduces the cost of the simulation by removing time dependency, at the cost of a small penalty in the accuracy of the time-averaged flowfield and lift distribution on the wing.
70 citations
TL;DR: In this article, the origin of the oscillation modes of screeching round jets is investigated by assuming that the feedback part of the aeroacoustic loop responsible for screech noise can be modeled by considering the neutral acoustic wave modes of the equivalent ideally expanded jets.
Abstract: In this Note, the origin of the oscillation modes of screeching round jets is investigated by assuming that the feedback part of the aeroacoustic loop responsible for screech noise can be modeled by considering the neutral acoustic wave modes of the equivalent ideally expanded jets.
68 citations
TL;DR: In this article, the shape optimization of a swept natural-laminar-flow wing in the transonic regime is studied, where the difficulty is associated with reliable prediction of laminar-turbulence transit.
Abstract: Aerodynamic shape optimization of a swept natural-laminar-flow wing in the transonic regime is still challenging. The difficulty is associated with reliable prediction of laminar–turbulence transit...
68 citations
TL;DR: The results demonstrate that the greedy non-intrusive ROM predicts the flow field accurately and efficiently.
Abstract: A greedy nonintrusive reduced order method (ROM) is proposed for parameterized time-dependent problems with an emphasis on problems in fluid dynamics. The nonintrusive ROM (NIROM) bases on a two-le...
TL;DR: In this article, multifidelity surrogates (MFS) combine low-fidelity models with few highfidelity samples to infer the response of the high-Fidelity model for design optimization or uncertainty quantification.
Abstract: Multifidelity surrogates (MFS) combine low-fidelity models with few high-fidelity samples to infer the response of the high-fidelity model for design optimization or uncertainty quantification. Mos...
TL;DR: Digital Thread is a data-driven architecture that links together information generated from across the product lifecycle that is gaining traction as a digital communication framewoman.
Abstract: Digital Thread is a data-driven architecture that links together information generated from across the product lifecycle. Though Digital Thread is gaining traction as a digital communication framew...
TL;DR: In this paper, an explorative investigation was performed to demonstrate the feasibility of using a thermal effect induced by dielectric-barrier discharge plasma generation for aircraft icing mitigation.
Abstract: An explorative investigation was performed to demonstrate the feasibility of using a thermal effect induced by dielectric-barrier-discharge plasma generation for aircraft icing mitigation. The expe...
TL;DR: In this paper, boundary layer ingestion (BLI) was used to generate a propulsive force with lower flow power input than conventional engines, and the aerodynamic benefit can be traced back to its sources: reducti...
Abstract: Propulsors with boundary layer ingestion (BLI) generate a propulsive force with lower flow power input than conventional engines. This aerodynamic benefit can be traced back to its sources: reducti...
TL;DR: The Hyperloop is a ground-based transportation system concept slated to drastically reduce travel times over medium range distances, for example between San Francisco and Los Angeles, and this paper presents a demonstration of this concept.
Abstract: The Hyperloop is a ground-based transportation system concept slated to drastically reduce travel times over medium range distances, for example between San Francisco and Los Angeles. This paper di...
TL;DR: Dynamic stall represents a challenge in a number of engineering applications including rotorcraft, maneuvering aircraft, gust encounters, and wind turbines.
Abstract: Dynamic stall represents a challenge in a number of engineering applications including rotorcraft, maneuvering aircraft, gust encounters, and wind turbines. Delay of the onset of dynamic stall and ...
TL;DR: The results confirm that the sweeping jet actuators are more effective than steady blowing and steady vortex-generating jets for this ramp configuration and suggest that an actuator with a wider jet spreading placed closer to the flow separation location provides better performance.
Abstract: A parametric experimental study was performed with sweeping jet actuators (fluidic oscillators) to determine their effectiveness in controlling flow separation on an adverse pressure gradient ramp. Actuator parameters that were investigated include blowing coefficients, operation mode, pitch and spreading angles, streamwise location, aspect ratio, and scale. Surface pressure measurements and surface oil flow visualization were used to characterize the effects of these parameters on the actuator performance. 2D Particle Image Velocimetry measurements of the flow field over the ramp and hot-wire measurements of the actuator's jet flow were also obtained for selective cases. In addition, the sweeping jet actuators were compared to other well-known flow control techniques such as micro-vortex generators, steady blowing, and steady vortex-generating jets. The results confirm that the sweeping jet actuators are more effective than steady blowing and steady vortex-generating jets. The results also suggest that an actuator with a larger spreading angle placed closer to the location where the flow separates provides better performance. For the cases tested, an actuator with an aspect ratio, which is the width/depth of the actuator throat, of 2 was found to be optimal. For a fixed momentum coefficient, decreasing the aspect ratio to 1 produced weaker vortices while increasing the aspect ratio to 4 reduced coverage area. Although scaling down the actuator (based on the throat dimensions) from 0.25 inch x 0.125 inch to 0.15 inch x 0.075 inch resulted in similar flow control performance, scaling down the actuator further to 0.075 inch x 0.0375 inch reduced the actuator efficiency by reducing the coverage area and the amount of mixing in the near-wall region. The results of this study provide insight that can be used to design and select the optimal sweeping jet actuator configuration for flow control applications.
TL;DR: The size of the vertical tail and rudder of a commercial aircraft is influenced by the requirement that the airplane must be controllable in the event of an engine failure.
Abstract: The size of the vertical tail and rudder of a commercial aircraft is influenced by the requirement that the airplane must be controllable in the event of an engine failure. As a result, on twin-eng...
TL;DR: In this article, the dominant fluid structures and unsteady behavior of the three-dimensional transonic buffet phenomenon on a swept wing are clarified, focusing on a well-established buffet phenomenon.
Abstract: The dominant fluid structures and unsteady behavior of the three-dimensional transonic buffet phenomenon on a swept wing are clarified. This paper focuses on a well-established buffet phenomenon ra...
TL;DR: In this paper, the flow over a flat-plate wing passing through a transverse gust was investigated using both experimental and computational methods, and the gust created physically in a water-filled towing tank was f...
Abstract: The flow over a flat-plate wing passing through a transverse gust was investigated using both experimental and computational methods. The gust created physically in a water-filled towing tank was f...
TL;DR: This paper develops a method for uncertainty quantification in feedback-coupled systems that leverage adaptive surrogates to reduce the number of cases for which fixed point iteration is needed.
Abstract: Fixed point iteration is a common strategy to handle interdisciplinary coupling within a feedback-coupled multidisciplinary analysis. For each coupled analysis, this requires a large number of disc...
TL;DR: In this article, a lightweight satellite structure based on lattice sandwich panels is designed, where all panels are manufactured from aluminum alloy AlSi10Mg by direct metal laser melting.
Abstract: L ATTICE sandwich structures arousemuch attention in recent two decades because of their outstanding performance in stiffness, strength, energy absorption, and the multifunctional design [1–4]. When subjected to a deformation dominated by stretching, lattice sandwich structures demonstrate preferable weight-efficiency compared with bending-dominated structures such as honeycomb sandwich structures [5–7]. Various techniques can be implemented to fabricate lattice sandwich structures, such as investment casting, deformation forming, and woven metal textiles [8–10]. However, traditional manufacturing techniques cannot achieve a satisfactory precision and geometrical complexity that are oftentimes simultaneously required by satellite structures. In recent years, the development of additive manufacturing techniques, such as selective laser melting and electron beam melting, makes the high-precision lattice structures become reality [11–13]. The geometric precision of the lattice has been reduced to submillimeter scale. The deformation behavior of the lattice sandwich plate has been studied via both numerical analysis and experimental testing. It is found that multiple factors, such as the parent material, the shape and size of the cell, as well as the connectivity, can influence themechanical properties of the lattice sandwich plate [5]. In aeronautic and aerospace applications, an increasing number of brackets based on lattice sandwich structures have been designed. However, to our best knowledge, the large-scale assembly structure such as satellite structure based on lattice sandwich structures has not been yet verified by experiments. In this paper, a lightweight satellite structure based on lattice sandwich panels is designed. In this satellite structure all panels are manufactured from aluminum alloy AlSi10Mg by direct metal laser melting. The dimensions of the structure are 400 × 400 × 400 mm, whereas its mass and carrying capacity reach 8 and 104 kg, respectively. The structure’s weight–to–satellite weight ratio is 7.7% in comparison to the ratio about 15–25% of minisatellites (satellites with the weight in the range from 100 to 500 kg) made of traditional aluminium honeycomb sandwich panels. Results of vibration tests reveal that the satellite structure could endure vibration loads entailed by the rocket launching.
TL;DR: The location of transition onset predicted from the simulation including the freestream spectrum, receptivity, and the linear and the weakly nonlinear evolutions yields a solution close to the measured onset location for the sharp cone.
Abstract: Boundary-layer transition in hypersonic flows over a straight cone can be predicted using measured freestream spectra, receptivity, and threshold values for the wall-pressure fluctuations at the tr...
TL;DR: In this article, four types of polymer/ceramic pressure-sensitive paints with reduced surface roughness were developed for measuring unsteady pressure fields in transonic flow, and they were tested on transonic flows.
Abstract: Polymer/ceramic pressure-sensitive paints with reduced surface roughness were developed for measuring unsteady pressure fields in transonic flow. Four types of polymer/ceramic pressure-sensitive pa...
TL;DR: In this paper, a thermoacoustic interpretation of second-mode instability is proposed, and it is demonstrated that the fundamental mechanism of secondmode wave growth in hypersonic boundary layers is consiste...
Abstract: A thermoacoustic interpretation of Mack’s second-mode instability is proposed. It is demonstrated that the fundamental mechanism of second-mode wave growth in hypersonic boundary layers is consiste...
TL;DR: In this paper, a low-dimensional active subspatial subspace is defined, where the dependence of a quantity of interest (e.g., a design objective or constraint function) on the design variables is analyzed.
Abstract: Design and optimization benefit from understanding the dependence of a quantity of interest (e.g., a design objective or constraint function) on the design variables. A low-dimensional active subsp...
TL;DR: In this paper, the location, strength and structure of tip and edge vortices shed from wings and bodies can be manipulated by using flow control techniques. Flow physics of these approaches involve flow separation f...
Abstract: Location, strength, and structure of tip and edge vortices shed from wings and bodies can be manipulated by using flow control techniques. Flow physics of these approaches involve flow separation f...
TL;DR: The Navier-Stokes equations were used in computational fluid dynamics analyses of high-Reynolds-number flows as mentioned in this paper, and the associated closure models are based on multiple simplifying assignments.
Abstract: Computational fluid dynamics analyses of high-Reynolds-number flows mostly rely on the Reynolds-averaged Navier–Stokes equations. The associated closure models are based on multiple simplifying ass...