The current experimental investigation explores the viscous/inviscid interaction of a supersonic turbulent boundary layer and a sharp fin-generated shock wave. The study examines the effect of Reynolds numbers on the fin-generated shock-wave/boundary-layer interactions (SBLIs) and the practical limits imposed on such scaling due to different test facilities. The present study involves a parametric

A recent structural model of a plate is extended to include a nonuniform temperature differential that varies in time using a modal expansion. The nonlinear structural plate model with first-order piston theory aerodynamics and cavity dynamics is coupled with the heat equation to form a single system of dynamical equations for the fluid-structural-thermal system. The heat flux from the boundary layer

Lateral–directional stability is a critical issue for the design of any kind of aircraft. For the hypersonic waverider, the nonaxisymmetric, flat, and slender geometric feature makes it susceptible to the problem of lateral–directional instability. Therefore, the influence of geometric feature on the lateral–directional static and dynamic stability of hypersonic waverider is studied so as to enable

This paper investigates the effect of external expansion ramps on supersonic flow emitted from high-aspect-ratio rectangular nozzles with a focus on additional sources of noise due to ramps as well as their effectiveness as noise reduction devices. Schlieren videos showed that the extended ramps stabilized the jet, reduced spreading, and elongated the shock cell systems. Far-field acoustics revealed

AIAA Journal, Ahead of Print.

This paper proposes an improved design methodology and global optimization method for the design of an advanced dropped-hinge flap (ADHF) using an integrated approach. The approach implemented an actuation-driven parametric model for a hinged-flap concept. The optimization methodology incorporates an adaptive data sampling method in the update of a series of surrogate models. Inclusion of an actuation

A series of flight experiments have demonstrated a novel approach to measuring path-resolved optical turbulence quantities, such as Cn2, along an air-to-ground slant path. This paper describes the data acquisition experiments that involved two laser beams propagating between an orbiting airborne platform and a stationary ground terminal over an 8 km slant path. Ground-based and in-flight measurements

In this paper, a functionally graded material column that is simply supported at one end and clamped at the other is considered. The buckling mode is postulated as a high-order polynomial. Six novel closed-form solutions are found by the semi-inverse technique. These solutions can be used as benchmark problems with which numerous approximate solution techniques can be tested. Technical novelty consists

Fluidically oscillating jet actuators that generate sweeping jets when supplied with a pressurized fluid have been used to mitigate separation and reduce drag in a range of flow control applications. Their implementation in future flight vehicles would require fundamental understanding and accurate predictive techniques of the physics of their internal flow and jet formation. The present investigations

Fundamental understanding of chemical kinetics pathways involved in ignition and flame propagation in hydrocarbon flames is essential for designing efficient and clean combustion devices for aerospace applications. In this study, spherically propagating methane-air and methane-ethane-air flames inside a constant-volume vessel were characterized using a species-specific, high-speed chemiluminescence

Existing models of extended-tube liners are mainly applicable to the normal-incidence case, and the influence of the grazing-flow effect is often ignored. In the current paper, an impedance model is developed based on the transfer matrix method, and the grazing-flow effect on the surface impedance is taken into account in terms of the end corrections. The validity of the model is examined on a flow-duct

Small unmanned aerial vehicles (SUAVs) operating in urban environments must deal with complex wind flows and endurance limitations caused by current battery technology. Birds offer inspiration regarding how to fly in these environments and how to exploit complex wind flows as an energy source. On a broad scale, migrating birds adjust airspeed to minimize cost of transport (COT) in response to wind

Robustly identifying nonlinear mechanical systems is generally a challenging task, and this is particularly true when the structure under test exhibits nonlinear behaviors related to both stiffness and damping. In this work, a hybrid nonlinear identification approach is proposed by combining the restoring force surface (RFS) method and the nonlinear subspace identification method. The multiparameter

AIAA Journal, Ahead of Print.

This paper proposes a unified solution for in-plane vibration analysis of laminated arbitrary polygonal plates based on the Chebyshev polynomial method. As an innovative point of present work, the arbitrarily shaped polygonal plate is composed of two arbitrarily shaped quadrilateral plates rigidly coupled for simulation. The quadrilateral plate is uniformly mapped into a unit square plate through the

The velocity field over a two-dimensional wing at Reynolds number of 672,000 was investigated to characterize the three-dimensional topology and evolution of the separate flow with variation of the angle of attack. Planar particle image velocimetry over the full span of the wing demonstrated that with increasing angle of attack, isolated pockets of backflow, which appeared near the trailing edge, merged

Adjoint methods are widely used for turbomachinery aerodynamic shape optimization. However, for industrial applications, the degradation of robustness and efficiency of adjoint solvers for edge-of-the-envelope conditions still poses a challenge to the successful deployment of adjoint methods in the industry. This work attempts to alleviate such problems by using the Newton–Krylov method to solve both

In hypersonic flows, it is often necessary to be able to trip the transition to turbulence, upstream of air intakes, for example. Direct numerical simulations have been performed to identify the roughness-induced transition mechanisms on a wedgelike forebody at Mach 6 and unit Reynolds number Re=11 million (/m). Good agreement with the experiments performed in the Boeing/Air Force Office of Scientific

Crossflow instability (CFI) is crucial for triggering boundary-layer flow transition over a transonic natural laminar flow (NLF) wing, whose leading edge is swept for reducing wave drag. This paper proposes a new flow parameter called the nondimensionalized crossflow pressure gradient (CFPG) to combine the effects of both wing sweep and pressure distribution on crossflow, which enables an alternative

AIAA Journal, Ahead of Print.

AIAA Journal, Ahead of Print.

AIAA Journal, Ahead of Print.

Flight and ground test applications for in-flow and near-wall flow temperature sensing demand robust and accurate sensing, making thermocouple sensors attractive. Even for these extremely well-developed sensors, an accurate prediction of stresses within thermocouple sheaths for custom-configured probes remains a topic of great concern for ensuring an adequate lifetime of sensors. In contemporary practice

Turbulence grids replicating the velocity profile (including the high-frequency part of the turbulence spectrum) of the atmospheric boundary layer (ABL) have been designed, manufactured, and tested in ONERA wind tunnels. These ABL grids are intended to improve the experimental simulation of the flow entering air inlets of aircraft engines while operating in a crosswind. It was found that the grids

This work considers aeroelastic modeling of the NACA 0012 benchmark wing, a configuration previously tested in the Transonic Dynamics Tunnel for flutter. Numerical modeling is conducted within the FUN3D Reynolds-averaged Navier–Stokes–based flow solver, with a particular focus on multiscale mesh adaptation and linearized frequency domain computations. Flutter results are obtained and compared with

This paper is devoted to the robust optimization of nacelle liners (acoustic treatments). The full computational aeroacoustic model is based on the convected Helmholtz equation in presence of a nonhomogeneous flow velocity field, which is computed by solving the potential Euler equations. Uncertainties are taken into account in order to increase the robustness of the predictions. A reduced-order computational

AIAA Journal, Ahead of Print.

AIAA Journal, Ahead of Print.

Three-dimensional high-fidelity numerical simulations of a Mach 5 hypersonic ramjet intake are performed combining a high-order and time-accurate large-eddy-simulation model with a sharp-interface immersed boundary method. The analysis provides a detailed characterization of the unsteady behavior of the intake. A systematic investigation is carried out varying the blockage of the intake channel, and

AIAA Journal, Ahead of Print.

The present work experimentally investigates two forcing strategies toward controlling stationary crossflow instability (CFI) induced transition manifesting on a swept wing at subsonic conditions. The effectiveness of upstream flow deformation (UFD) and the base-flow modification strategies, realized through the application of spanwise-modulated and spanwise-uniform dielectric barrier discharge plasma

A structured Reynolds-averaged Navier–Stokes solver is directly coupled to a linear stability theory (LST) solver to include the effect of laminar–turbulent transition in the flow simulations. The flowfield variables of the flow solver are used to both find streamlines along which transition can be predicted and to provide the LST code with the required boundary-layer profiles. Instabilities included

AIAA Journal, Ahead of Print.

AIAA Journal, Ahead of Print.

Design optimization problems with black-box computation-intensive objective and constraints are extremely challenging in engineering practices. To address this issue, an efficient metamodel-based optimization strategy using parallel adaptive kriging method with constraint aggregation (PAKM-CA) is proposed. In PAKM-CA, the complex expensive constraints are aggregated using the Kreisselmeier and Steinhauser

A 10%-scale high-lift version of the Common Research Model (CRM-HL) was tested in the NASA Langley Research Center’s 14 by 22 ft subsonic tunnel. The focus of the wind-tunnel tests was to investigate the vortices generated at the nacelle/pylon region and their effect on the aerodynamic performance. The wind-tunnel measurements included the acquisition of force and moment data, steady pressure data

Airfoil design generally involves high dimensionality and nonlinear mappings, leaving the preferred infill sampling strategies in the framework of Bayesian optimization uncertain across instances and changeable in the sequential optimization stages. Knottily, no single-infill sampler guarantees the optimal results for airfoil design for its changeless intrinsic selection mechanism, whereas parallel

The three-dimensional steady incompressible numerical results of an isothermal flowfield resulting from the interaction of two swirl-stabilized air nozzles in a multiple lean direct injection combustor configuration are analyzed. The spacing between nozzles S is varied from 1.1 to 2.72 nozzle diameters d to analyze the degree of swirl interaction between them and their impact on the resulting flow

We attempt to detect a precursor of thermoacoustic combustion oscillations in a staged multisector combustor for an aeroengine by the combined methodology of recurrence-based analysis and machine learning. Combustion experiments are conducted at the combustor inlet temperature and pressure of 740 K and 1340 kPa, respectively. The joint dimensional vicinity Jd and the determinism of recurrence plots

A wavelet-based optical flow analysis (wOFA) method for processing background-oriented schlieren (BOS) images is presented and demonstrated on synthetic and experimental data. Optical flow is inherently well suited to BOS, because the background pattern and lighting conditions are specified and controlled by the user and can be chosen to play to the strengths of optical flow processing. Analysis of

In this study the effect of film cooling on entropy wave attenuation and indirect entropy noise generation was investigated in a subsonic stator blade row with a leading-edge, pressure-side, and suction-side cooling geometry. The investigation was conducted on a small blade midspan section (in a linear cascade arrangement), using a three-dimensional unsteady Reynolds-averaged Navier–Stokes simulation

This paper focuses on resonant ice protection systems and proposes key performance indicators to analyze the performances of such systems with respect to levels of energy, force, and power required for de-icing. The principle of these systems is to apply vibrations or ultrasonic waves onto the structure that create high-level stresses greater than those required to crack and delaminate to remove the

This paper presents a new approach for mitigating the unphysical delay in the Reynolds-averaged Navier–Stokes (RANS) to large-eddy simulation (LES) transition, often referred to as the gray area, which is a common issue for hybrid RANS–LES turbulence models such as delayed-detached eddy simulation. An existing methodology designed for improving the LES performance in complex flows is adapted and tested

Hypersonic vehicles operate at extreme environments at narrow margins of safety. High-speed flight in the atmosphere when volcanic ash and other meteorological particles are present can cause damage to these vehicle surfaces, impairing heat transfer and damaging sensitive components, leading to failure. Upon surveying typical conditions for solid particles that might be encountered, it was determined

This paper presents two methods to design cutouts that allow damage-free folding of the stiffest possible composite self-deployable thin shell structures of complex shapes. The first method uses level-set functions that define a general number of cutouts. The second method uses a spline representation of the contour of a single cutout and optimizes its shape. Material failure detection is implemented

An aerodynamic model for applications to external flows is formulated that provides a great tradeoff between computational cost and prediction accuracy. The novelty of the work is the ability to deal with any unsteady flow problem, irrespective of the frequency of motion and motion kinematics. The aerodynamic model, baptized FALCon, combines an in-house unsteady vortex lattice method with an infinite-swept

As a typical morphing wing, a folding wing with structural nonlinearities may encounter complex nonlinear aeroelastic effects during the in-flight morphing process. This paper presents a novel parameterized modeling methodology for efficient modal and nonlinear aeroelastic analysis of a folding wing with bilinear hinge stiffness and the variation of the folding angle. The most attractive feature of

Direct numerical simulations were carried out for a straight and a flared cone at Mach 6 and zero angle of attack to investigate the effects of geometry on the linear and nonlinear stages of the laminar–turbulent transition process. The cone geometries and the flow conditions of the simulations are chosen to closely match those of the experiments conducted at the Boeing/AFOSR Mach 6 Quiet Tunnel (BAM6QT)

This paper presents two enhancements of the efficient broadband time-domain impedance model proposed by Dragna, Pineau, and Blanc-Benon in 2015. It treats lined walls in the framework of the macroscopic concept of locally reacting acoustic impedance, and allows the formulation of the time-domain impedance boundary condition in the form of a set of ordinary differential equations. The first, minor,

AIAA Journal, Ahead of Print.

Numerical calculations were carried out in order to investigate the delay of transition to turbulence on a wing section by means of local dynamic surface deformation. Physically, the deformation may be produced by piezoelectrically driven actuators located below a compliant aerodynamic surface, which have been explored experimentally. One actuator was located in the upstream region of the wing, and

An explicit dynamic simulation of the vertical crash of a regional airliner’s middle fuselage section has been conducted to investigate its crashworthiness. The simulation result shows that there are two major acceleration peaks in the crashing process when the crash velocity is 9.14 m/s. The initial acceleration peak is 15.8 g, and the secondary acceleration peak is 24.2 g with a duration of 0.02 s

In the cutout reinforcement for a stiffened cylindrical shell, the layout optimization of global stiffeners and the stiffeners around the cutout are generally separated. However, considering the two optimizations separately is noncollaborative. To solve this problem, a global–local collaborative optimization method is proposed. Based on the sequential sampling method, a set of sampling points is obtained

An axisymmetric viscous shock tube simulation code is developed that keeps the shock and the contact discontinuity stationary in suitably constructed moving frames of reference. The flowfield around the discontinuities is represented on fine grids that move with the frames attached to the waves. These moving grids are overset upon a coarse background grid of the entire facility, allowing efficient

Large-eddy simulations are performed to investigate the dynamic response of a natural laminar flow airfoil undergoing harmonic small-amplitude pitch oscillations at a chord based Reynolds number of Rec=750,000. Large changes in the transition location as well as trailing-edge separation are observed throughout the pitch cycles, which leads to a nonlinear response of the aerodynamic forces. Despite

AIAA Journal, Ahead of Print.

AIAA Journal, Ahead of Print.

This paper investigates self-excited oscillation within a slat cove and the flowfield parameters involved in selection of the main oscillation mode. Aeroacoustic experiments are described for aerodynamic noise characteristics on the leading-edge slat of a two-dimensional three-element high-lift configuration. Different geometrical settings are tested at varying angles of attack. A numerical simulation

AIAA Journal, Ahead of Print.

Shock-capturing methods for numerical fluid dynamics are capable of correctly representing the flow conditions across shocks. However, there is no guarantee that the methods remain equally applicable for unsteady problems of shock–disturbance interaction. Based on the results of wide parametric computations, this paper demonstrates an inherent weakness of shock-capturing methods related to an ambiguous