Uncertainty based multidisciplinary analysis (UMDA) is a methodology to quantify uncertainty on the system-level quantity of interest by propagating uncertainty within and among multiple disciplines of a system. In an industrial setting, the design of complex systems involves the collaboration of multiple and diverse teams involving high-fidelity disciplinary tools and experts. Under such scenarios

An experimental study is conducted on a NACA 0012 airfoil with a control surface to investigate the influence of a propeller slipstream under a low-Reynolds-number condition. To investigate the influence of the propeller slipstream on a wing surface, the flowfield on the wing surface is visualized using a temperature-sensitive paint when the chord-based Reynolds number is equal to 3.0×104. The control

Flying animals exploit highly nonlinear dynamics to achieve efficient and robust flight control. It appears that the distributed flow and force sensor arrays found in flying animals are instrumental in enabling this performance. Using a wind-tunnel wing model instrumented with distributed arrays of strain and pressure sensors, we characterized the relationship between the distributed sensor signals

To ensure the aerodynamic performance of the slat in aircraft when retracted, it is necessary to set rubber seals in the seam between the leading-edge slat and the fixed leading edge. However, the extrusion and friction of the seal will induce the increment frictional loading on the slat driver. In the present Paper, a rigid–flexible body configuration model of the increment frictional loading was

For small short/vertical takeoff and landing (S/VTOL) unmanned aerial vehicles, the propeller design should reach a compromise between S/VTOL and cruise. But the complexity cost of a variable-pitch propeller is too high to be applied to small propellers. To achieve the propeller pitch variability with minimum mechanic complexity and weight cost, an aerostable concept was used in the design of the blades

Research interest is growing for theoretical models of highly deflected structures in aeroelastic settings. Presented here is a model of a cantilevered plate subjected to axial supersonic flow to determine the flutter boundary and postflutter characteristics of a system such as a trailing edge control surface. The structural model is a nonlinear inextensible beam model with inertia and stiffness geometric

A first principles physics-based simulation framework that accounts for wind-over-deck (WOD) and ground effects during approach and landing of a helicopter on a ship deck is developed. The WOD velocities are obtained from unsteady detached-eddy simulation of the flow over a simple frigate shape version 2 ship. The HeliUM2 flight dynamics code was modified to include WOD, static and dynamic ground effects

Urban air mobility refers to an envisaged air taxi service, using small, autonomous, vertical-takeoff-and-landing, battery-powered electric aircraft. A conceptual design and optimization tool for urban air mobility, including vehicle, mission, and cost models, is presented in this paper. The tool uses geometric programming, a class of optimization problems with extremely fast solve times and for which

Journal of Aircraft, Ahead of Print.

Journal of Aircraft, Ahead of Print.

The flows past morphing cavities with different ramps of the leading wall and the fixed ramp of the trailing wall were investigated with direct numerical simulation and dynamic mode decomposition to analyze the oscillation phenomena. Based on the analysis of pressure signal and sound pressure level spectra obtained by direct numerical simulation, an interesting fact is found that there is a transition

The paper presents computational prediction of aerodynamic hysteresis loops in static conditions for a two-dimensional aerofoil that was used as a cross-section profile for a rectangular wing with an aspect ratio of five, tested in the TsAGI T-106 wind tunnel at a Reynolds number of Re=6×106 and a Mach number of M=0.15. Tests in the wind tunnel showed that minor changes in the curvature of the leading

Technology forecasting is an essential starting point for conceptual design of any complex engineering system. In fact, many research projects are focused on developing a small set of promising technologies to a suitable readiness level. However, selecting a set of technologies from a larger pool is a nontrivial task, opposed by uncertainty and subjective tradeoffs. This paper proposes a probabilistic

In forward flight, slowing down a rotor alleviates compressibility effects on the advancing side blade tip, extending the cruise speed limit, and inducing high-advance-ratio flight regime. Previous wind tunnel tests have shown that an articulated rotor trimmed to zero hub moment generates limited thrust at high advance ratios, because the advancing side needs to be trimmed against the retreating side

Journal of Aircraft, Ahead of Print.

Spatially distributed load on aircraft structures is difficult to obtain due to the limitation of measurement technology, the complexity of load and the external environment of the aircraft during flight, etc. A load identification method based on a subregion interpolation technique is proposed to indirectly estimate the distributed dynamic load from measured strain data on planar structures. The load

Conceptual sizing and performance estimation of four vertical takeoff and landing (VTOL) configurations for a package delivery mission is presented in this Paper. The multifidelity VTOL design framework HYDRA is used to size a notional quadrotor, hexarotor, quadrotor biplane tailsitter (QBiT), and a lift-augmented tricopter for weight classes of 10, 15, 20, and 25 kg. Sizing is performed using a combination

Journal of Aircraft, Ahead of Print.

Journal of Aircraft, Ahead of Print.

The modeling of different problems in aeroelasticity requires a time-domain equation of motion, especially to design modern controllers and study nonlinear characteristics. Typically, unsteady aerodynamic forces are written in the (reduced) frequency domain and then rewritten using rational function approximations in the time domain. In this context, this Paper presents an investigation of this topic

Journal of Aircraft, Ahead of Print.

In recent years, multilayered hierarchical compositions of the well-known and widely used Gaussian process models called deep Gaussian processes are finding use in the approximation of black-box functions. In this paper, the performance of deep Gaussian process models is empirically evaluated and compared against the well-established Gaussian process models with a special emphasis on engineering problems

This paper uses gradient-based optimization to minimize the mass of a solar-regenerative high-altitude long-endurance flying-wing aircraft while accounting for nonlinear aeroelastic effects. The aircraft is designed to fly year round at 35° latitude at 18 km above sea level and subjected to energy capture, energy storage, material failure, local buckling, stall, longitudinal stability, and coupled

The present Paper investigates the ditching characteristics of a helicopter model by means of an in-house-developed smoothed-particle-hydrodynamics solver coupled with a six degree-of-freedom motion equation. Verification and validation have confirmed the feasibility and accuracy of the developed solver in predicting hydrodynamic problems. In view of the inherent importance, the effect of initial pitching

In this Paper, the wake dynamics of coaxial rotors are studied using the high-wake-resolution method. The high-wake-resolution method is a novel combination of the truncated vortex tube model for initial and boundary conditions and the wave-number-extended finite-volume interpolation scheme. The wake resolution of this method is verified by comparison with other general computational fluid dynamics

Air traffic controller workload is considered to be a limiting factor for further air traffic growth. To reduce workload, increased automation levels and novel decision-support tools are being investigated. This Paper describes the adaptation and evaluation of a previously developed interface, called the Solution Space Diagram, in a route merging task. It portrays both constrained and unconstrained

Some of the existing challenges of fixed-wing micro aerial vehicle designs at low Reynolds number are low lift and reduced aerodynamic efficiency. Delta wings, despite their characteristic maneuverability, are rarely used for micro aerial vehicles, perhaps due to the limited lifting capacity because of the reduced aspect ratio. Corrugations on insect wings are ubiquitous and augment the aerodynamic

Droplet deformation and breakup in the continuously accelerated flowfield generated by an incoming airfoil have been studied. The upper limit of droplet deformation and the minimum distance to the airfoil model at which the breakup onset takes place have been modeled. Three analytical equations have been developed based on the combination of two models: a droplet deformation and trajectory model for

A 10%-scale high-lift version of the Common Research Model and an active flow control (AFC) version of the model equipped with a simple-hinged flap were successfully tested. The main objective of the test was to develop an AFC system that can provide the necessary lift recovery on a simple-hinged flap high-lift system while minimizing its pneumatic power requirement. The tests were performed in the

A simple, accurate, reduced-order model is developed for predicting the maximum available thrust performance of subsonic ring-wing propulsors varying in shroud airfoil length, thickness, camber, and/or angle of attack relative to the centerline. The method, applicable to drones, aircraft, ships, and more, identifies the potential upper limit to the thrust augmentation available from hover to cruise

Recent aircraft noise calculation methods separate engine and airframe noise components to provide accurate single-flight noise predictions. General noise mapping, such as legal compliance calculations, usually relies on position data as the only available input. Therefore, more advanced input variables of engine and airframe noise models require estimation based on position data. This paper presents

Regime recognition (RR) is an important aspect of condition-based maintenance for modern helicopters. RR involves the postflight classification of flight data into regime categories. These classifications are then used to predict fatigue damage and vehicle usage spectra. Although several RR algorithms have been proposed to date, many suffer from an overreliance on training data or poor accuracy when

Because of the large domestic civil aircraft projects started in China a decade ago, there is a greater need to control the accuracy of the Mach number in aerodynamic tests, especially near the designed cruise point of large commercial aircraft. Nowadays the control accuracy of China Aerodynamics Research and Development Center 2.4-meter transonic wind tunnel Mach number is in the range of ±0.002 to

This paper presents a thorough evaluation of three flutter prediction techniques based on the well-understood autoregressive moving-average (ARMA) parametric model. Other than the original stability parameter Fz that is derived from the identified autoregressive coefficients, the flutter margin and the Houbolt–Rainey (H-R) method are also presented and adjusted to provide alternative flutter predictions

In this Paper, the integrated propeller–wing system design space is investigated to gain insight into the influence of propeller diameter, location, and rotation direction. To conduct this investigation, a methodology is developed that uses the propeller power required during steady-level flight as a metric for efficiency. Full mutual interaction between the propeller and wing are taken into account

This work presents the aeromechanics analysis and evaluation of an ultralight counter-rotating coaxial rotorcraft using a combined numerical and experimental approach with a focus on turn, climb, and descent flight conditions. The helicopter features a 2-by-2 bladed coaxial rotor system with teeter hinges, 6.5 m in diameter and uniform airfoil sections of the linearly twisted blades. Hover and forward-flight

An advanced potential flow method is used to study the aerodynamic interactions between small rotors of quadrotor configurations and the impact on the overall flight performance. The aerodynamic analysis method is validated by comparing the thrust and power predictions of isolated rotors in hover and forward flight with experimental results. The aerodynamic model was next extended to consider the interactions

We discuss the requirements of a predictive microburst flight trajectory guidance system, and analyze the trajectories of low thrust-to-weight ratio airplanes passing through a microburst downdraft and vortex ring along the approach glideslope. The simulation results reveal that it is possible to fly through such a microburst using 5–20 deg pitch angle and maximum thrust. T tests and one-way analysis

Control surface reversal is a classical aeroelastic phenomenon commonly investigated during aircraft development. It occurs under static equilibrium between the elastic restoring torque and the aerodynamic moment on the system. Besides the equilibrium, it depends on an additional condition defined through the lift force. As discussed in the literature, this second condition can be considered by two

Boundary-layer ingestion (BLI) promises increased aircraft efficiency, but excessive inlet distortion must be avoided to prevent fans that are too heavy or structurally infeasible. We propose a new approach to study the effect of distortion on BLI propulsors via an aeropropulsive design optimization with a constraint on inlet distortion using highly efficient gradient-based methods with analytic derivatives

An experimental remotely piloted aircraft named X-HALE was designed and built at the University of Michigan to collect experimental data for the flight dynamics of vehicles with very flexible wings. Similar aircraft with a wing span of 4 and 6 m were later developed and built at the Aeronautics Institute of Technology, Brazil, to study the flight dynamics and control of highly flexible aircraft. In

The hinge clearance and rotation axis deviation of aircraft landing-gear retraction mechanism are unavoidable due to factors, such as manufacture, assembly, wear, and wing deformation. Such negative factors affect the dynamic response of the mechanism itself, which is more serious for spatial mechanisms. To study this effect, both numerical and experimental investigations on a spatial landing-gear

This paper studies the influence of flared-hinge folding wingtips on the aerodynamic derivatives and flight dynamics of a narrow-body transport aircraft. In addition, the influence of fold angle, hinge-line angle (flare angle), and wingtip size on wing loading is assessed. The Tornado vortex lattice method is used for aerodynamic predictions and to estimate the stability and control derivatives. First

Journal of Aircraft, Ahead of Print.

The mean flowfield in the aft region of cargo aircraft configurations is analyzed using large-eddy simulations. A simplified surrogate fuselage is considered, consisting of a cylinder with axis parallel to the flow and a slanted (upswept) base. Emphasis is placed on understanding the major changes that occur in the flow as the upsweep angle of the base is increased in a broad 20°–45° range. Qualitative

This paper conducts improved delayed detached eddy simulation (IDDES) to numerically investigate the performance of a three-dimensional (3D) aircraft control surface using coflow jet (CFJ) active flow control. For the numerical validation with the baseline control surface that has a large flow separation, the predicted lift coefficient CL and drag coefficient CD achieve a very good agreement with the

A key challenge in the design of hybrid-electric propulsion systems (HEPSs) for aircraft is the complexity involved in handling efficient sizing of the components as well as control synergy between multiple power sources. To handle this challenge effectively, combined optimal design and control (codesign) methods that enable the integration of energy management optimization along with vehicle sizing

Journal of Aircraft, Ahead of Print.

The pursuit of greener aviation led to the investigation of new aircraft concepts. Disruptive aircraft configurations show great potential in reducing the ground noise impact, but extensive research is required before they can be manufactured. Tube-and-wing aircraft with over-the-wing engines, benefiting from noise shielding, are a more feasible option for midterm noise reduction targets. This work

Journal of Aircraft, Ahead of Print.

By using a computational-fluid-dynamics-based numerical virtual flight (NVF) simulator, a simplified quasi-Cobra maneuver of a typical third-generation fighter is simulated and the unsteady aerodynamics, such as the dynamic forces and moments and the flow separation, are analyzed preliminarily. The NVF simulator integrates an unsteady Reynolds-averaged Navier–Stokes (RANS) solver on dynamic unstructured/hybrid

Journal of Aircraft, Ahead of Print.

The quad tilt rotor (QTR) has complex aerodynamic characteristics and strong aerodynamic interference. The flight dynamic model is the basis of control. To effectively account for the aerodynamic interference between the multiple aerodynamic surfaces of the QTR unmanned aerial vehicle, a hybrid optimization trimming analysis method based on Immune Algorithm/Levenberg–Marquardt (IA/LM) and lattice Boltzmann

The rotor blade double-swept-tip geometry can effectively improve the aerodynamic and aeroacoustic behaviors of a rotor. However, the aeroelastic or aeromechanical behaviors of a double-swept rotor helicopter are a challenge to helicopter flight safety and need to be investigated. In this paper, the aeromechanical stability of a bearingless rotor helicopter with double-swept blades is studied. The

As multirotor vehicles become integrated into the national airspace for applications such as package delivery and videography, it is important that the inner-loop control system be robust and able to meet ever-demanding performance constraints. To achieve high bandwidth control designs, it is necessary to have accurate and high bandwidth open-loop models. In this Paper, a linear state-space model of

Recent research on flight-deck interval management technology, including the findings of a flight-test demonstration conducted by NASA, led to the development of an alternative control logic for flight-deck interval management, termed as “interval management–speed planning.” As this logic demonstrated promising results in numerical simulations, for the first time, test pilots and airline pilots were

Journal of Aircraft, Ahead of Print.

Journal of Aircraft, Ahead of Print.

This Paper describes a new method of correcting the wind tunnel wall interference of permeable Kevlar test section walls. The classical three-dimensional panel method is extended to flows in a Kevlar-walled test section and modified to improve its general predictability. The results computed using this enhanced panel method are in good agreement with experimental results with regard to the pressure

Journal of Aircraft, Ahead of Print.