AIAA Journal, Volume 59, Issue 3, Page 764-764, March 2021.

Dynamic effects of wing planform changes are investigated with the goal of gust alleviation. Force measurements are done on a low-aspect-ratio high-angle-of-attack translating wing having a rectangular planform that incorporates a moving tip with in-plane rotation and sweep. To create streamwise gusts, the wing is towed in a water tank from constant motion to a new velocity that is 50% higher (“step-up”)

This paper aims to study the lift response of transverse and vortex gust encounters. A sine-squared transverse gust was created in a water towing tank using a water jet, whereas a vortex gust was created in a water channel by clockwise half-rotation of an upstream gust generator plate. Forces and flowfields were acquired for both gust types. The effects of the gust ratio and vertical positioning of

AIAA Journal, Volume Virtual Collection, Issue 3, Page 764-764, March 2021.

Most of the sensitivity algorithms with respect to the design parameters adopted the normalization relationship with system property matrices weighted when analyzing an asymmetrical damping linear discrete dynamic system. In this paper, two new methods (an algebraic method and a direct method) based on the Euclidean norm as the normalization conditions are proposed. Both proposed methods are developed

AIAA Journal, Ahead of Print.

This paper presents a numerical model that assesses the effect of applying transpiration cooling to both the outer wall and the substructure of a high-speed flight vehicle. The porous impulse response analysis for transpiration cooling evaluation (PIRATE) code has been extended and validated to account for quasi-two-dimensional lateral heat conduction effects, thereby allowing for analysis of more

In this paper, the restart processes of two generic rectangular hypersonic inlets with different internal contraction ratios have been experimentally studied under a freestream Mach number of 5.0. The experimental results show that without downstream throttling, both inlets start successfully after the flowfield establishment of the wind tunnel. To obtain the restart processes of the two inlets, they

A sharp-interface immersed-boundary method that does not smear the boundaries, is easy to implement, and is straightforward in handling the Neumann condition as compared to previous methods is developed for compressible flows to simulate the interaction of solid particles with shocks. The inviscid and viscous fluxes of compressible flow equations in curvilinear coordinates are discretized with a third-order

A nonlinear model is developed to investigate the blade vibration-induced acoustic resonance in a linear cascade. The Euler equations are solved by using high-order computational aeroacoustics techniques. To satisfy no-penetration wall boundary conditions for vibrating blades, a semi-implicit time-accurate body force model is developed. Leading-edge singularity at resonance is remarkably strong, and

Acoustic data measured in a fan test facility with and without an inflow control device (ICD) over the inlet were analyzed using the cyclostationary analysis technique, which separates the total power into a rotor-locked and a fluctuating component. Measurements were taken with an inlet mode detection ring upstream of the rotor and with far-field microphones for configurations with subsonic and with

The flame front of a premixed ethylene–air turbulent flame in a high-speed flowfield was imaged using hydroxyl radical (OH) planar laser-induced fluorescence (PLIF). An electrically heated continuous flow facility produced inflow conditions with a total temperature of 1200 K, corresponding to a flight Mach number of about five. A statistically stationary turbulent flame stabilized over a scaled-down

A large-eddy simulation is performed on a single nonrotating airfoil with tip gap in order to highlight the noise sources in the tip-leakage flow. The geometry is composed of a NACA 5510 airfoil (5% camber, 10% thickness) mounted between two flat plates, with a 10 mm tip gap between the airfoil and one of the plates. The Reynolds number based on the chord is 960,000 and the Mach number is 0.2. The

Traditional adjoint variables grow exponentially for turbulent chaotic flows. Most proposed methods (for example. ensemble adjoint, shadow-based, and unstable-subspace-based approaches, etc.) are computationally prohibitive for practical problems. In the current paper, we evaluate a stabilization approach for the adjoints of turbulent flows, which is computationally cheap compared to the previously

Unsteady aerodynamic shape optimization presents new challenges in terms of sensitivity analysis of time-dependent objective functions. In this work, we consider periodic unsteady flows governed by the unsteady Reynolds-averaged Navier–Stokes (URANS) equations. Hence, the resulting output functions acting as objective or constraint functions of the optimization are themselves periodic with unknown

A novel configuration of focused laser differential interferometry (FLDI) was developed, simulated, and tested. The new configuration is referred to as cylindrical FLDI or CFLDI. Using cylindrical lenses in place of standard lenses changes the three-dimensional shape of the focusing beam from a cone shape for FLDI to a triangular sheet for CFLDI, allowing for probing of flat-plate boundary layers closer

Surface roughness elements are often used to force laminar to turbulent transition in aerodynamic and aeroacoustic wind-tunnel experiments. The statistical features and spectral content of the pressure fluctuations in the resulting turbulent boundary layer at the trailing edge can affect far-field noise. To elucidate this dependence, boundary-layer transition induced by randomly distributed roughness

AIAA Journal, Ahead of Print.

This work introduces an aeroelastic optimization framework with a coupled three-dimensional panel method and Timoshenko beam finite element model. The method allows for optimization of both the exterior surface of the wing and interior structural properties. We investigate the effects of curved wall spars on the aeroelastic performance of converged designs, which have been shown to provide an improved

AIAA Journal, Ahead of Print.

A new numerical method to efficiently simulate particulate interactions with high-speed transitional boundary-layer flows is presented. A particulate solver, employing Crowe’s correlation, is used to calculate the particulate trajectory. The solver is fully coupled via a particulate–flow interaction source term to a nonlinear disturbance flow solver based on the compressible Navier–Stokes equations

AIAA Journal, Ahead of Print.

Super-cooled large droplets (SLDs) present a unique experimental challenge for conventional horizontal spray icing wind tunnels due to gravity effects on the droplets and coalescence between the particles. Limited ice accretion shapes in this regime exist, making the verification of modeling tools and the validation of the applicability of scaling methods difficult. Furthermore, SLD accretions often

An actuator surface model has been developed that couples an aerodynamics model to a computational fluid dynamics solver. The model is designed for simulation of rotors in complex operating environments, and it advances a recently developed actuator surface model through the addition of two new elements: a computational fluid dynamics (CFD)-convected wake model, and an improved coupling algorithm.

The deflagration-to-detonation (DDT) run-up distance LDDT for small-sized tubes is an important parameter for determining the position of a detonation initiation in the pulse detonation propulsion device as well as industrial safety. However, its variation tendency is insufficiently clarified, owing to complex multiple competing mechanisms between the properties of mixtures and the negative displacement

The adjoint state of a nonlinear vortex-lattice method, coupled with sectional polars obtained with an infinite swept-wing (2.5D) Reynolds-averaged Navier–Stokes (RANS) solver, is presented as an interactive method for preliminary aerodynamic design and control of moderate-to-high aspect ratio wings in subsonic and transonic flows. First, the nonlinear vortex-lattice method is described, augmented

Morphing wings are expected to have transformative impact on future transportation and energy systems. To enable analysis and optimization of morphing wings, efficient numerical models are critically important. In this work, we present an accurate and tractable reduced-order model embedded in a genetic-algorithm-based optimization framework. The modeling and optimization framework allows concurrent

This study deals with the development of a numerical wire mesh screen model for the unsteady simulation of aeroacoustic configurations. Such devices are indeed of growing interest for practical applications because they potentially lead to significant noise-reduction effects. Numerical simulations including wire mesh screens are therefore of major interest to optimize their possible location and properties

The stress-intensity factors of box beams under torsion and crack propagation under torsion or/and bending moment are discussed here. This study is motivated by a previous work [1] that derived a closed-form expression of the mode II stress-intensity factor for thin-walled beams with a centered longitudinal crack and subjected to torsion. Naturally, the way in which mode I stress-intensity factors

Mesh generation and deformation are critical elements in gradient-based aerodynamic shape optimization (ASO). Improperly generated or deformed meshes may contain bad-quality cells that degrade the accuracy of computational fluid dynamics (CFD) solvers. Moreover, an inefficient mesh deformation method can become the bottleneck for the entire ASO process. To perform practical ASO, mesh generation and

We study the collective response of synthetic hair sensors to changes in the airflow direction. Specifically, we examine whether an array of isotropic sensors, which are unable to detect the direction of an incident flow when operating in isolation, can together sense not only the magnitude but also the orientation of a freestream flow passing over and through them. To conduct our inquiry, we consider

The bimodal behavior of turbulent junction flows is associated with a low-frequency unsteadiness that can have implications for the overall performance of engineering applications. The literature suggests that the bimodal behavior may be correlated with upstream boundary-layer events. To test this hypothesis, large-eddy simulations of a generic junction flow with Rood wing geometry were performed for

The objective of multifidelity modeling is to achieve both accurate and efficient predictions by combining high- and low-fidelity models. A flexible approach considering additive, multiplicative, and input correction factors is proposed to improve the low-fidelity model using high-fidelity data. The correction factors are estimated using a Bayesian approach. Collection of high-fidelity data is optimized

Straight-bladed crossflow turbines are computationally explored for harvesting energy in wind and water currents. One challenge for crossflow turbines is the transient occurrence of high apparent angles of attack on the blades that reduces efficiency due to flow separation. This paper explores kinematic manipulation of the apparent angle of attack through intracycle control of the angular velocity

High-speed aerospace engineering applications rely heavily on computational fluid dynamics (CFD) models for design and analysis. This reliance on CFD models necessitates performing accurate and reliable uncertainty quantification (UQ) of the CFD models, which can be very expensive for hypersonic flows. Additionally, UQ approaches are many-query problems requiring many runs with a wide range of input

Separated flows arising due to shock-wave/turbulent boundary-layer interactions can cause problematic low-frequency unsteadiness with potentially severe structural response. High-fidelity large-eddy simulations are employed to examine surface morphing as a way to reduce the size of the separation region, and thus favorably alter the unsteadiness characteristics. The configuration considers a turbulent

AIAA Journal, Ahead of Print.

The structural dynamics of turbomachinery bladed disks is of paramount importance to ensure safety and reliability. Due to their sensitivity to mistuning (that is, any deviation from nominal properties), bladed disk vibrations encountered in practical applications can be significantly amplified. Thus, it is important to identify mistuning of as-manufactured blisks so that computational models can be

This paper presents a theoretical model based on Biot theory to investigate the sound transmission loss (STL) of a pyramidal lattice sandwich structure lined with porous material. This theory is more accurate than equivalent methods and suitable for use in different complex filling configurations. Several filling patterns with different boundary conditions are studied, and their governing equations

This work discusses the design, measurement, and simulation of an oscillating shock-wave/boundary-layer interaction on a flat plate at Mach 5.8 and Re∞=7×106 m−1. The shock generator is free to pitch and oscillates with a frequency of 42 Hz, resulting in a shock that varies in intensity and impingement point, with a maximum flow-deflection angle of approximately 10 deg. Transition appears to take place

A large number of deployable space structures involve multibody system dynamics, and in order to effectively analyze and optimize dynamic performance, the sensitivity information of multibody systems is often required. At present, the sensitivity analysis methods of multibody system dynamics, which have been widely used, are mainly finite difference method, direct differentiation method, and adjoint

AIAA Journal, Ahead of Print.

An electromechanically coupled zigzag theory is presented for static and free vibration responses in functionally graded material (FGM) plates bonded with piezoelectric layers. It has the capability to consider continuity as well as discontinuity in material properties at all interfaces. The displacement field approximation, which is initially layer based, has been made layer independent by using continuity

This paper explores the operating envelope for the University of Queensland’s free-piston driven X2 expansion tube to determine if flow conditions can be produced that generate a significant magnetohydrodynamic interaction. Numerical calculations are presented to demonstrate the existence of viable operating conditions to study magnetohydrodynamics. Argon is selected as the test gas due to its simple

Dielectric barrier discharge (DBD) plasma actuators were implemented on the leading edges of Wells turbine impeller blades for the purpose of controlling leading-edge separation, and the turbine performance was recorded. Pulse-modulated perturbations at dimensionless frequencies near unity produced remarkable increases in performance. Under massively stalled conditions, with upstream angles of attack

Bioinspired surface riblets have been known to improve drag performance by altering the near-wall flow structures, especially in the transitional flow regime. Unlike conventional riblet geometries (for example, sawtooth and scalloped shapes) overlaid on flat plates, the use of a new Gaussian-shaped abstraction overlaid on three-dimensional (3-D) airfoil surfaces is conceived in this paper. Given the

We carry out a parametric study of conical shock-wave/turbulent boundary-layer interactions by means of numerical simulation of the Reynolds-averaged Navier–Stokes (RANS) equations, with the eventual goal of establishing the predictive capabilities of standard turbulence models. Preliminary assessment of several linear-eddy-viscosity models for the case of planar interactions shows that the k−ε model

Three-dimensional transient dynamics of a towed system is investigated in this paper. The tow cable is modeled as a geometrically exact (GE) beam, and the payload is a rigid body. The GE beam model incorporates large displacements and rotations of the cable, including cross-sectional shear, which is impossible in current models. Time-domain electromagnetic (TDEM) systems, used in mineral surveying

An experimental investigation is conducted to study the effect of multiscale endplates on the wing-tip vortex and wing aerodynamic performance at Reynolds numbers of 215,000 and 244,000 based on the wing mean chord of a NACA 0012 half-span wing. Two groups of endplates are tested. The first group has three different fractal patterns applied along the top edge of the endplate, while the second group

The mechanism of the supersonic round jet mixing enhancement by a pulsed energy deposition is studied numerically by solving the three-dimensional unsteady Reynolds-averaged Navier–Stokes equations with the second-order scheme in space and time. A round jet at different Mach numbers (Mj=1.05, 1.76, 3.00) is parallelly injected into a coflowing air stream of Mach number 2.5, interacting with the oblique

This paper reports wall-modeled large-eddy simulation (WMLES) results of low-speed turbulent flows in a plane channel, in ribbed ducts, and around a film cooling jet. We compare our WMLESs to Pirozzoli et al.’s direct numerical simulations (DNSs) of low-speed plane channel flow (Pirozzoli, S., Bernardini, M., and Orlandi, P., “Passive Scalars in Turbulent Channel Flow at High Reynolds Number,” Journal

Dynamic effects of wing planform changes are investigated with the goal of gust alleviation. Force measurements are done on a low-aspect-ratio high-angle-of-attack translating wing having a rectangular planform that incorporates a moving tip with in-plane rotation and sweep. To create streamwise gusts, the wing is towed in a water tank from constant motion to a new velocity that is 50% higher (“step-up”)

The computational cost associated with simulating fluid flows can make it infeasible to run many simulations across multiple flow conditions. Building upon concepts from generative modeling, we introduce a new method for learning neural network models capable of performing efficient parameterized simulations of fluid flows. Evaluated on their ability to simulate both two-dimensional and three-dimensional

The validity of numerical modeling of discharge plasma in dielectric barrier discharge plasma actuator is evaluated by comparing the simulation and experimental results under the same conditions. Discharge plasma behavior is numerically simulated based on a three-fluid plasma model. Regarding the induced jet structure, although the simulation tends to underestimate the jet thickness and overestimate

Crackle is a perceptual feature of supersonic jet noise that is related to the presence of acoustic shocks. This study investigates the apparent source locations of the steepest shocklike events in the noise field of a high-performance military jet aircraft using an event-based time-domain beamforming method. This method uses the cross correlation between adjacent microphones to determine the angle

The longitudinal dynamic characteristics of a 60 deg sweptback delta-wing model at angles of attack of up to 21 deg were investigated in this study using a magnetic suspension and balance system. The magnetic suspension and balance system can obtain wind-tunnel data without support interference by suspending a model using magnetic forces. Wind-tunnel tests during accurate pitch oscillations were conducted

AIAA Journal, Ahead of Print.

This work introduces a novel structural concept for morphing wings, based on carbon-fiber reinforced polymer (CFRP) lattice structures. Conventional wing spars and ribs are replaced by CFRP rods, which are arranged with varying orientation and distribution within a load-carrying wing skin. A new structural parametrization is introduced to define the internal lattice structure. By adapting the orientation

It is well known that the nonlinear response of a beam or plate is sensitive to the assumptions made about the in-plane boundary constraints. This is true for any static or dynamic loading, and especially for aerodynamic loads that may lead to a dynamic instability and limit cycle oscillations. In the present paper, a mathematical and computational model for the general case has been created to allow

An efficient implicit Fourier time-spectral method is developed for the unsteady Reynolds-averaged Navier–Stokes (URANS) computations of turbulent flows. In addition to the time-spectral URANS equations, the time-spectral Spalart–Allmaras turbulence model equation is also solved by the space–time lower-upper symmetric Gauss–Seidel (LU-SGS) implicit scheme. The efficient LU-SGS sweeps are directly extended