AIAA Journal, Ahead of Print.

A large space antenna structure will inevitably vibrate due to the space thermal environment and maneuver actions of the satellite. Such vibration will last continuously and affect normal function of the antenna. Therefore, a proper vibration control method is vital to keep the shape accuracy of the structure within an acceptable range. The research object of this paper is a large deployable planar

Wall pressure fluctuations beneath a boundary layer are the main cause of structural vibration for hypersonic aircraft. To accurately predict the load environment of pressure fluctuations, a measurement in a hypersonic wind tunnel was carried out to investigate the characteristics of wall pressure fluctuations generated by different flow types. In the measurement, a linear sensor array was used to

In the present study, large-eddy simulations of a three-dimensional flow around the NACA 0015 wing controlled by a dielectric-barrier-discharge (DBD) plasma actuator (PA) were conducted, and the influence of the wing tip on the flow was investigated. A half-span rectangular wing with an aspect ratio (AR) of two was selected. The Reynolds number was set to 63,000, and the angles of attack were 12 and

Recent interest in flight through gusty winds has given rise to a large body of work on discrete large-amplitude gust encounters where the magnitude of the flow disturbance is large enough to incite massive flow separation. This paper outlines and introduces work performed as part of the North Atlantic Treaty Organization’s Science and Technology Organization’s Task Group AVT-282 on the unsteady aerodynamic

The stability of a two-dimensional hypersonic flat-plate boundary layer with a shallow cavity is investigated at Mach 6 using direct numerical simulations. The boundary layer is perturbed by a single-frequency wall blowing–suction actuator. The results indicate that the second mode is damped when the cavity is placed slightly downstream of the synchronization point (SP) of mode F and mode S, whereas

AIAA Journal, Ahead of Print.

An experimental investigation has been conducted on swept impinging oblique shock/boundary-layer interactions at a nominal Mach number of 2.28 with a fully turbulent incoming boundary layer (Reθ=5500). The swept impinging oblique shock is induced by shock generators with x-y plane deflection angle θ=12.5 deg and various x-z plane sweep angles ψ=15.0, 22.5, 30.0, and 40.0 deg. Oil flow visualization

Helicopter operations on frigates imply complex maneuvers for pilots. During the aircraft approach to the frigate, the helicopter rotor is immersed in a changing aerodynamic flow, with high speed and turbulence intensity gradients. This occurs as a consequence of the nonaerodynamic surfaces that compose the frigates and generate detached flow on their decks. Typically, the helicopter operations on

AIAA Journal, Ahead of Print.

Indirect noise due to the interaction of flow inhomogeneities with a choked nozzle is an important cause of combustion instability in solid rocket motors and is believed to be important in aircraft engines. A previously published experiment (Kings, N., and Bake, F., “Indirect Combustion Noise: Noise Generation by Accelerated Vorticity in a Nozzle Flow,” International Journal of Spray and Combustion

Two-dimensional (2-D) strip-theory modeling of unsteady gust–airfoil interaction is standard practice in many industrial applications, but the limits of applicability of 2-D unsteady flow modeling on three-dimensional (3-D) wing and rotor geometries are not well understood. This paper investigates the effects of 3-D geometry features (such as finite span, taper, sweep, and rotation) on the unsteady

The reduction of aircraft noise over the past decades has generated a growing awareness that the characteristics of a signal can be equally or more important to annoyance than the sound pressure level. Sound can be perceived as more annoying, depending on the frequency content or tonal components. The sound quality metrics loudness, roughness, sharpness, and tonality are important tools to characterize

We present applications of laser-energy deposition for drag reduction in supersonic flow. The system of chemically reactive Navier–Stokes equations describes the hydrodynamics where nonequilibrium effects are accounted for by means of a two-temperature model. The propagation and attenuation of the laser beam are modeled based on a kinetic approach for photons (radiative transfer equation). Multiphoton

Some recent developments in the Lamb-vector-based aerodynamic force breakdown used the concept of vortex force to define the lift and to decompose the drag into lift-induced drag and profile drag. However, the Lamb vector formulation involves moment transformations, and the associated force breakdown may depend on the reference point adopted for their computation. Yet, the force acting on an airplane

The development of space mission requires the lightweight, large deploying-to-folding ratios and high-precision deployable structures. The tape-spring hinge can achieve a deflection of 180 deg within a 5% elastic deformation range. For one triangular prism mast (TPM) with the tape-spring hinges, the equivalent beam model for the TPM is derived using an energy equivalence method. The node deflections’

In the aerodynamic characteristics of supersonic parachutes, it is important to understand surface pressure distribution because it is strongly related to the fluctuation of drag and problematic unstable deformation of a parachute. However, there is a paucity of studies that focuses on the detailed surface pressure distribution. Therefore, we investigated the interior and exterior of a rigid disk-gap-band-type

AIAA Journal, Ahead of Print.

Strain-rate-based damping is investigated in the strong form of the intrinsic equations of three-dimensional geometrically exact beams. Kelvin–Voigt damping, often limited in the literature to linear or two-dimensional beam models, is generalized to the three-dimensional case, including rigid-body motions. The result is an elegant infinite-dimensional description of geometrically exact beams that facilitates

AIAA Journal, Ahead of Print.

Three-dimensional flow development is experimentally assessed in a convectively unstable laminar separation bubble formed over a NACA 0018 airfoil at a chord Reynolds number of 125,000, an angle of attack of 4 deg, and a freestream turbulence intensity of 0.07%. The flow is weakly excited in a spanwise uniform manner at a frequency matching that of the most unstable disturbances in the natural separation

A large variety of gusts that develop in the atmospheric boundary layer affect aerial vehicles. This study, performed in water tow tanks, compares the response of a flat plate wing to transverse vertical gusts with a top-hat and a sine-squared velocity profile at Reynolds numbers of 20,000–30,000. Experiments are performed for a wide range of gust ratios (0.5–1.5) and angles of attack (0–20 deg). Force

A recent reduction technique for the nonlinear forced response analysis of structures with contact interfaces is upgraded. The evaluations of the existing method (Dual formulation), which is based on dual Craig–Bampton method, show its considerable off-line computational time saving because of no matrix manipulation, whereas the resulting reduced model is less accurate than Rubin’s in approximating

Large-eddy simulation (LES) of an RG-15 airfoil in clean (that is, nonturbulent) flow is conducted at a Reynolds number of 1.07×105 with and without the formation of ice on its leading edge. The characteristics of the ice-induced separation bubble (ISB) and its influence on the aerodynamic performance are studied at low angles of attack (AOA=0, 3, and 6 deg). These are compared to the naturally developed

This Paper presents a new quasi-steady in-ground effect (IGE) model for small multirotor aerial vehicles such as quadcopter unmanned aerial vehicles. The model offers three major advances to the state of the art: 1) predicting the IGE thrust ratio without singularity, 2) relating the strength of the ground effect to the blade geometry (pitch angle, solidity, and radius), and 3) capturing the effect

The continuous detonation engine (CDE) is based on detonation waves and is a new jet engine concept that is expected to bring a technical revolution to current aviation and aerospace propulsion systems. Some scholars have also called this concept the continuously rotating detonation engine or rotating detonation engine. The advantages and application potential of the CDE have been widely recognized

A gradient-based multistart method based on a set of 17 to 33 random initial geometries is used to examine the risk associated with multimodality when applying gradient-based optimization to aerodynamic shape optimization. Aerodynamic shape optimization problems typical of detailed, preliminary, and exploratory design are shown to consistently present design spaces with multiple local optima. In the

In this study, numerical simulations of spatially developing incompressible turbulent boundary layers (SDTBLs) with adverse pressure gradient (APG) over two-dimensional smooth curved ramps have been performed by solving the Reynolds-averaged Navier–Stokes (RANS) equations. First, it has been verified that the RANS results converge with respect to domain and grid size, and the effects of different inflow

A semi-empirical estimate of the time-averaged thickness of a planar shock embedded in a turbulent mean flow is presented in an effort to quantify the characteristic time and length scales for turbulence modeling. Simplified Favre-averaged Navier–Stokes equations are reformulated and combined with the Rankine–Hugoniot relations to obtain an equation that relates the shock structure and its characteristic

AIAA Journal, Ahead of Print.

This work deals with the development of an improved numerical model, based on the explicit finite element method, aimed at investigating the energy absorption capabilities of a full-scale composite fuselage section of a regional aircraft and the related biomechanical injuries affecting the passengers. The experiment, conducted within the Italian national research project named “Innovative and Advanced

Linear and nonlinear models have been studied in the past for supersonic starting flow due to forward step motion of an airfoil where the airfoil gains an angle of attack. This Paper considers the inverse problem, supersonic stopping flow due to backward step motion of a flat plate, where the plate initially having an angle of attack reduces its angle of attack to a smaller one. The wave structures

A smooth version of the γ-R˜eθt local correlation-based transition model (LM2015) for the Spalart–Allmaras (SA) turbulence model is presented. The LM2015 model with helicity-based crossflow correlations is modified and coupled to the SA turbulence model, designated SA-LM2015. The LM2015 and SA-LM2015 transition models include source terms that contain stiff and nonsmooth functions. Approximations to

AIAA Journal, Ahead of Print.

To investigate the mechanism of wave trapping, acoustic embedded trapped modes associated with two-resonant-mode interference in two-dimensional duct–cavity structures are calculated by the feedback-loop closure principle, which allows us to analyze the traveling modes that construct the trapped modes. The exact two coexisting resonant modes that underpin an embedded trapped mode in a cavity open to

An experimental study has been carried out to determine the influence of a forward facing-step (FFS) on the laminar–turbulent transition of a swept wing boundary layer. Wind tunnel experiments were conducted at a fixed 3 deg angle of attack and varying Reynolds number between 2.5 and 4.5 million. Moreover, the FFS influence was investigated under unforced (i.e., smooth leading edge) and forced conditions

A computational investigation of the role of thermal nonuniformity on the development of instability modes in the shear-layer of a supersonic M=1.5, Re=850,000 jet is performed in this study. Cold fluid is injected at the axis of a heated jet to introduce radial nonuniformity and control the spatial development of shear layer. This is a companion investigation of an experimental study that observed

Wakes behind turbomachine blades are generally highly turbulent and seemingly chaotic. Within the apparent chaos, coherent structures of various strength and length scales are present that are challenging to identify within individual snapshots of the wake flowfield. We propose a strategy to identify and separate multiscale vortices in the turbulent wake of a turbomachine blade from experimental data

Shock tunnel experiments are presented that examine combustion modes of ethylene and a 64/36% ethylene/methane mixture under Mach 8 flight-representative conditions within an axisymmetric scramjet cavity combustor. Combustion modes (scram-mode and dual-mode) are presented via streamwise pressure measurements and visualized via planar laser-induced fluorescence (PLIF) of the hydroxyl (OH) combustion

The origin of the noncirculatory force arising during a cylinder sharp-edged gust encounter is investigated experimentally at a Reynolds number of 6000. Planar particle image velocimetry and force balance measurements are employed simultaneously to assess the response of a translating cylinder encountering nominal gust ratios of 0.5, 1, and 1.5. Although the vortex sheet distribution, which represents

A plane vibration study of a sandwich thermal protection system insulation panel with a functionally graded core is conducted. The panel is assumed to be under plane-stress conditions and subjected to simply supported boundary conditions. The two-dimensional elasticity formulations are used to derive the equations of motion for each layer. The effects of the in-plane normal stresses as well as the

The inclusion of transition-to-turbulence effects in computational fluid dynamics simulations is essential to accurately predict drag reduction from the use of laminar flow technologies. The parabolized stability equation (PSE) method takes into account nonlocal and nonparallel effects on boundary-layer dynamics. Its computational cost compares to that of linear stability theory (LST) analysis, which

The present paper introduces mixed unified particle swarm optimization (MUPSO) algorithm to detect and quantify the delamination damages in composite beams and plates using vibration responses. MUPSO is a combination of conventional continuous unified particle swarm optimization (UPSO) and a binary version of UPSO, which is proposed in this paper. The first few modes have been used to detect delamination

The assessment of uncertainties is essential in aerodynamic shape optimization problems to come up with configurations that are more robust against operational and geometrical uncertainties. However, exploring the stochastic design space significantly increases the computational cost. The aim of this paper is to develop a framework for efficient optimization under uncertainty by means of a bilevel

In this work, three-component planar velocity measurements are analyzed to identify the effects of compressibility on mixing layer turbulence, with a focus on the evolution of large-scale structures, dominant spatial eigenmodes, and entrainment length scales. Velocity measurements obtained via stereoscopic particle image velocimetry for five different dual-stream air planar mixing layers with convective

Active flow control to delay the flow separation on the rudder of two different models has been investigated in the ONERA L1 wind tunnel. The first model was used as a simplified test case to investigate different types of actuations and consisted of a flat plate with a rudder. The different types of actuation investigated were continuous/pulsed blowing through slots, continuous blowing through segmented

Flow and noise solutions of the two Large-Eddy Simulation (LES) approaches are evaluated for the jet flow conditions corresponding to a benchmark coaxial jet case from the European Union Computation of Coaxial Jet Noise experiment. The jet is heated and issues for a short-cowl axisymmetric nozzle with a central body at a transonic speed. The first LES method is based on the Compact Accurately Boundary-Adjusting

The flow enthalpy of an arc-heated wind tunnel is an important parameter for reproducing planetary entry and performing heating tests. However, its distribution is insufficiently clarified, owing to complicated phenomena, such as arc discharge and supersonic expansion. In this paper, the authors assess the enthalpy of an arc-heated flow in a large-scale facility based on measurements and computational

The directivity of noise from three large-eddy simulations of turbulent jets at Mach 0.7, 0.9, and 1.5 is investigated using spectral proper orthogonal decomposition (SPOD). The most energetic patterns of acoustic radiation are extracted using the far-field pressure 2-norm. Specialization of the norm to the far field is accomplished through localized spatial weighting. Radiation patterns to specific

Over the last few years, air lasing has emerged as an attractive topic in standoff detection research. However, existing approaches have relied on the major species of air as the gain medium. This work presents the first experimental demonstration of an air laser based on water vapor, a minor constituent of air. The approach relies on photodissociation of water vapor molecules followed by two-photon

This work demonstrates the control of the shock-induced separated flow generated by a sharp fin placed on a cylindrical surface (fin-on-cylinder shock-wave/boundary-layer interaction) with an incident Mach 2.5 flow. Well-quantified distortions in the form of streamwise vortices are embedded into the boundary layer using single sub-boundary-layer vortex generators (VGs). At four device heights downstream

A new algorithm for a flush air data sensing (FADS) system was developed to estimate flight data and attitude angles for a sharp-nosed hypersonic vehicle in a framework of a hypersonic flight demonstration project directed by the Japan Aerospace Exploration Agency at the Kakuda Space Center. The design’s target condition is Mach 5.0–7.0 with angles of attack and sideslip within 6°. The FADS system

A stationary wing placed in the wake of a bluff body experiences lift enhancement. The quasi-periodic flow in the wake causes excitation of the separated flow in the poststall conditions. The increase in the time-averaged lift force is associated with the flow separation, leading-edge vortex formation, and subsequent reattachment in a process similar to the dynamic stall of oscillating wings. The lift

Simulations are reported on the behavior of two tandem symmetric foils in an in-line configuration undergoing pitching motion. The Reynolds number was varied between 1000 and 4000, whereas the pitching Strouhal number ranged from 0.2 to 0.5 and the amplitude of pitching varied from 4 to 8 deg. The streamwise separation distance between the foils was fixed at one chord length. The performance of the

Advances in aerodynamic and propulsive efficiency of future aircraft can be achieved by strategic installation of propellers near the airframe. This paper presents a robust and computationally efficient engineering method to estimate the load distribution of a propeller operating in arbitrary nonuniform flow that is induced by the airframe and by different flight conditions. The time-resolved loading

Accuracy, robustness, and efficiency are the three major goals of turbulence closure. Generally, eddy-viscosity models (EVMs) with the Boussinesq approximation are numerically stable and efficient. However, the accuracy of EVMs for aerodynamically complex configurations is inadequate. Reynolds-stress models (RSMs) are perceived as the most advanced turbulence models, but their robustness and efficiency

Flow control of separation caused by transonic shock-wave/boundary-layer interaction (SWBLI) is investigated. The control of the unsteadiness associated with SWBLI is not an objective of this paper. A SWBLI in a transonic channel is considered, and Reynolds-averaged Navier–Stokes simulations are carried out to compute the flow in the test section. The massive separation due to the interaction is controlled

The influences of steps on the hypersonic boundary-layer transition on a cone are investigated in a hypersonic quiet wind tunnel, using high-frequency pressure sensors and nano-tracer-based planar laser scattering (NPLS) techniques. The high-frequency surface pressure fluctuations are analyzed using power spectral density analysis, band-pass filtering, and cross-correlation calculation. Quantitative

AIAA Journal, Ahead of Print.

AIAA Journal, Ahead of Print.