This paper aims at developing an aeroelastic model for the instability analysis of supersonic thick fins. To this aim the modal analysis technique is used for the structural dynamics modelling of a fin with a general structure. An unsteady aerodynamic model is applied based on the shock/expansion analysis over the flat surfaces of the fin along with local application of the piston theory. Assuming a supersonic fin with an arbitrary polygonal cross-section, thickness and initial angle-of-attack, the steady flow properties (e.g. Mach number, density and temperature) are calculated over the flat surfaces of the fin. Then, assuming small amplitude vibrations, the generalised aerodynamic forces are obtained in terms of the structural modal coordinates. Using the obtained model, the effect of thickness, initial angle-of-attack, taper ratio and sweep angle on the aerodynamic derivatives and aeroelastic stability of the fin are studied which show their remarkable effects on the instability Mach number and its type. Specially, the presented results show that increasing the fin thickness dramatically diminishes the stability margin mainly at low angles of attack. Also a sharp decrease of the divergence Mach number is observed by increasing the fin’s incidence angle.

The present paper describes the design of a hybrid actuation control concept, a fuzzy logic proportional-integral-derivative plus a conventional on-off controller, for a new morphing mechanism using smart materials as actuators, which were made from shape memory alloys (SMA). The research work described here was developed for the open loop phase of a morphing wing system, whose primary goal was to reduce the wing drag by delaying the transition (from laminar to fully turbulent flows) position toward the wing trailing edge. The designed controller drives the actuation system equipped with SMA actuators to modify the flexible upper wing skin surface. The designed controller was also included, as an internal loop, in the closed loop architecture of the morphing wing system, based on the pressure information received from the flexible skin mounted pressure sensors and on the estimation of the transition location.

The controller’s purposes were established following a comprehensive presentation of the morphing wing system architecture and requirements. The strong nonlinearities of the SMA actuators’ characteristics and the system requirements led to the choice of a hybrid controller architecture as a combination of a bi-positional on-off controller and a fuzzy logic controller (FLC). In the chosen architecture, the controller would behave as a switch between the SMA cooling and heating phases, situations where the output current is 0A or is controlled by the FLC.

In the design phase, a proportional-integral-derivative scheme was chosen for the FLC. The input-output mapping of the fuzzy model was designed, taking account of the system’s error and its change in error, and a final architecture for the hybrid controller was obtained. The shapes chosen for the inputs’ membership functions were s -function, π-function, and z -function, and product fuzzy inference and the center average defuzzifier were applied (Sugeno).

Consideration of the environmental impact of aircraft has become critical in commercial aviation. The continued growth of air traffic has caused increasing demands to reduce aircraft emissions, imposing new constraints on the design and development of future airplane concepts. In this paper, an aircraft design optimisation framework is used to design aircraft that minimise specific environmental metrics. Multidisciplinary design optimisation is used to optimise aircraft by simultaneously considering airframe, engine and mission. The environmental metrics considered in this investigation are CO2 emissions — which are proportional to fuel burn — and landing-takeoff NOx emissions. The results are compared to those of an aircraft with minimum direct operating cost. The design variables considered in the optimisation problems include aircraft geometry, engine parameters, and cruise settings. An augmented Lagrangian particle swarm optimiser and a genetic algorithm are used to solve the single objective and multi-objective optimisation problems, respectively.

The generation of a fully turbulent boundary layer profile is investigated using analytical and numerical methods over the Reynolds number range 422 ≤ Reθ ≤ 31,000. The numerical method uses a new mixing length blending function. The predictions are validated against reference wind tunnel measurements under zero streamwise pressure gradient. The methods are then tested for low and moderate adverse pressure gradients. Comparison against experiment and DNS data show a good predictive ability under zero pressure gradient and moderate adverse pressure gradient, with both methods providing a complete velocity profile through the viscous sub-layer down to the wall. These methods are useful computational fluid dynamic tools for generating an equilibrium thick turbulent boundary layer at the computational domain inflow.

This paper studies the rotor aeromechanics in descending flight using a nonlinear flexible multibody dynamic analysis code, DYMORE. A freewake model is included in DYMORE to improve the rotor wake modelling. The wind-tunnel test data of the Higher-harmonic Aeroacoustics Rotor Test (HART) II rotor, with and without higher harmonic pitch control (HHC), and the flight test data of the full-scale utility helicopter rotor in descent are used for the aeromechanics correlation at an advance ratio of 0·15. The blade-vortex interaction (BVI) airloads are reasonably predicted for both the HART II and utility helicopter rotors, although some BVI peaks are missed on the advancing sides for both the rotors. The flap deflections and elastic torsion deformations at the blade tip are fairly correlated against the measured data of the HART II rotor. The correlation of blade structural moments for both HART II and utility helicopter rotors are not as good as the lift predictions; however, a reasonable prediction is obtained for the utility helicopter rotor.

A Parabolised Navier-Stokes (PNS) flow solver is used to predict the aerodynamic heating on the surface of a hypersonic vehicle. This case study highlights some of the main heat flux sensitivies to various conditions for a full-scale vehicle and illustrates the use of different complimentary methods in assessing the heat load for a realistic application. Different flight phases of the vehicle are considered, with freestream conditions from Mach 4 to Mach 8 across a range of altitudes. Both laminar and turbulent flows are studied, together with the effect of the isothermal wall temperature, boundary-layer transition location and body incidence. The effect of the Spalart-Allmaras and Baldwin-Lomax turbulent models on the heat transfer distributions is assessed. A rigorous assessment of the computations is conducted through both iterative and grid convergence studies and a supporting experimental investigation is performed on a 1/20th scale model of the vehicle’s forebody for the validation of the numerical results. Good agreement is found between the PNS predictions, measurements and empirical methods for the vehicle forebody. The present PNS approach is shown to provide useful predictions of the heat transfer over the axisymmetric vehicle body. A highly complex flow field is predicted in the fin-body-fin region at the rear of the vehicle characterised by strong interference effects which limit the predictions over this region to a predominately qualitative level.

This contribution presents a novel simulation for a fixed-wing aircraft powered by gas turbine engines and advanced propellers (turboprops). The work is part of a large framework for the simulation of aircraft flight through a multi-disciplinary approach. Novel numerical methods are presented for flight mechanics, turboprop engine simulation (in direct and inverse mode), and propeller dynamics. We present in detail the integration of the propeller with the airframe, aircraft and tonal noise model. At the basic level, we address a shortfall in multi-disciplinary integration in turboprop-powered aircraft, including economical operations and environmental emissions (exhausts and noise). The models introduced are based on first principles, supplied with semi-empirical correlations, if required. Validation strategies are presented for component-level analysis and system integration. Results are presented for aerodynamics, specific air range, optimal cruise conditions, payload-range performance, and propeller noise. Selected results are shown for the ATR 72-500, powered by PW127M turboprop engines and F568-1 propellers.

This lecture recognises the background and distinguished work of Frederick William Lanchester, and notes that my background has a few similarities with his. These include a shared interest in wings, lift and vortices. My career at the NASA Langley Research Center spans the time-frame from America’s Super Sonic Transport through 2009. An early emphasis involved wind-tunnel testing of research aircraft models and the development of computer codes for subsonic aerodynamics of wing planforms. These attached-flow codes were applied to various configurations, including those with variable-sweep, dihedral, and more than one planform in both the analysis- and design-modes. These codes were used to provide a connection between leading-edge-forces and the associated additional lift on delta-wings with shed-vortex systems through the leading-edge suction analogy of Edward C. Polhamus. Subsequently, I extended the suction analogy to configurations with side-edges to predict the vortical-flow aerodynamics on complex configurations, including wing-strake combinations. These analysis codes could also be used in a design-by-analysis mode for configurations with leading-edge shed vortices. Later, I was involved in vortical-flow flight research with the F-106B and the F-16XL aircraft at cruise and maneuver conditions. Associated CFD predictions, generated by me and other members of the RTO/AVT-113 task group, have increased our understanding of the flight flow-physics measured on the F-16XL aircraft.

An overview of the major issues to be addressed for widespread commercial introduction and use of aviation biofuels is presented in this paper. These include the progress toward standards and approvals, bio-feedstock supply and sustainability, conversion routes to suitable fuel molecules, and policy and regulation considerations to create the necessary market and investment environment. It has been shown that while technical standards are now largely in place, biojet faces competition from biodiesel markets for feedstock, and existing sources of vegetable oil face sustainability challenges for greater supply. Other conversion routes exist that can use more sustainable feedstock, but they are capital intensive and will require a high fuel price to support investment. Policy approaches to cover the expected price premium above fossil fuel may also face political difficulties.

The aerodynamic shape optimisation of a micro air vehicle (MAV) wing is performed to obtain the basic wing geometrical characteristics which produce the maximum range and endurance requirements. Multhopp’s method based on Prandtl’s classical lifting line theory is used for the determination of the spanwise load distribution required during the optimisation process. The obtained lift and drag characteristics are used for the derivation of the range and endurance equations of an electrically driven micro air vehicle. The optimisation process is based on the modified feasible directions gradient based optimisation algorithm. Results are validated using wind tunnel measurements showing very good agreement. Results are also compared with solutions to the Navier-Stokes equations obtained with ANSYS-CFX finite elements using different turbulence models. These include the k-ε and the shear stress transport (SST) models as well as the Reynolds stress model.

In the present article, in-flight ice formation on finite wings and air intakes of low-speed aircraft are numerically studied. The approach to the problem involves calculation of the velocity field using a three-dimensional panel method. Using the calculated velocity field, the droplet trajectories and droplet impact locations are computed yielding the droplet collection efficiency distribution. In the next step, convective heat transfer coefficient distributions around the geometries are calculated using a two-dimensional Integral Boundary-Layer Method, which takes surface roughness due to ice accretion into account. A thermodynamic analysis employing the Extended Messinger Method yields the ice growth rates. Integration of these rates over time yields the ice shapes, hence the modified geometry. Predicted ice shapes are compared with experimental shapes reported in the literature and good agreement is observed. Ice shapes around vastly varying geometries including complex shapes are successfully computed. As such, the developed tool may be used for academical purposes or for airworthiness certification efforts.

This paper presents the design and implementation of a vision-based automatic guidance system on a fixed-wing unmanned aerial vehicle (UAV). The system utilises a low-cost ordinary video camera and simple but efficient image processing techniques widely used in computer-vision technology. The paper focuses on the identification and extraction of geographical tracks such as rivers, coastlines, and roads from real-time aerial images. The image processing algorithm primarily uses colour properties to isolate the geographical track of interest from its background. Hough transform is eventually used to curve-fit the profile of the track which yields a reference line on the image plane. A guidance algorithm is then derived based on this information. In order to test the vision-based automatic guidance system in the laboratory without actually flying the UAV, a hardware-in-the-loop simulation system is developed. Description regarding the system and significant simulation result are presented in the paper. Finally, an actual test flight where the UAV successfully follows a stretch of a river under automatic vision-based guidance is also presented and discussed.

Research by Rogers et al (2009) and Leland et al established that flight simulator training can improve a pilot’s ability to recover a general aviation aeroplane from an in-flight upset. To reach this conclusion, they administered simulator-based and classroom-based upset-recovery training to two groups of student pilots, then compared their performance in recovering an aerobatic Decathlon aeroplane from a series of four upsets with the performance of a third group of untrained control group pilots subjected to the same upsets. We extend this result by addressing the unanswered question of how much classroom-based training as opposed to simulator-based training contributes to improving a pilot’s upset-recovery manoeuvring skills. After receiving classroom-based upset-recovery training but no simulator training, our participants were subjected to the same series of four upsets in the same Decathlon aeroplane. We then compared the performance of the classroom-trained pilots with the performances of control group pilots and the two groups of simulator-trained pilots. Statistical analysis suggests that classroom-based instruction alone improves a pilot’s ability to recover an aeroplane from an upset. We summarise related research, describe the training experiment and the training program, analyse and interpret flight-test data, and explain what our research implies with respect to establishing career-long commercial pilot upset-recovery training requirements.

Design optimisation of a helicopter rotor blade is performed. The objective is to reduce helicopter vibration and constraints are put on frequencies and aeroelastic stability. The ply angles of the D-spar and skin of the composite rotor blade with NACA 0015 aerofoil section are considered as design variables. Polynomial response surfaces and space filling experimental designs are used to generate surrogate models of the objective function with respect to cross-section properties. The stacking sequence corresponding to the optimal cross-section is found using a real-coded genetic algorithm. Ply angle discretisation of 1°, 15°, 30° and 45° are used. The mean value of the objective function is used to find the optimal blade designs and the resulting designs are tested for variance. The optimal designs show a vibration reduction of 26% to 33% from the baseline design. A substantial reduction in vibration and an aeroelastically stable blade is obtained even after accounting for composite material uncertainty.

Today, all sailplanes in any particular class look and perform more or less the same. This gives credence to the view that the necessary compromises in design and sailplane technology have reached a limit. Sailplane development is on a sort of plateau. Further, apart from perhaps boundary-layer control (BLC), there appears to be nothing in the foreseeable future that promises any significant improvement in performance. It is the purpose of this paper to, once again, encourage interest in Variable Geometry (VG) and address the controversies which prevailed in abundance during the 1970s and which apparently still survive today.

In this paper, flow control effectiveness of a passive device in relation to open cavity flowfield is investigated computationally and compared with experimental work. Specifically the modification in the cavity flowfield due to the presence of a spoiler is studied in details to explain the physics behind the flow control effects. A combination of 2D and 3D flow visualisation tools are used to understand the flow behaviour inside the cavity and the quantitative analysis of the unsteady pressure fluctuations is also performed to assess the unsteady effects. Flow simulations with a turbulence model based on a hybrid RANS/LES (commonly known as Detached-Eddy Simulation (DES)) are used in this study. The time-mean flow visualisation clearly showed the presence of three dimensional effects inside the empty cavity whereas the 3D effects were found to diminish in the presence of a spoiler. In the unsteady flow analysis, near-field acoustic spectra were computed for empty cavity as well as cavity-with-spoiler cases. Study of unsteady pressure spectra for the cavity-with-spoiler case was found to record the complete suppression of the dominant tones in the presence of the spoiler. The analysis has indicated that the main reason behind this suppression is due to the inability of faintly energised vortical structures (faintly energised as a result of the extraction of turbulent kinetic energy by the spoiler) to maintain the unsteady flapping of the separated shear layer.

The paper presents the numerical and experimental validation of a hybrid actuation control concept – fuzzy logic proportional-integral-derivative (PID) plus conventional on-off – for a new morphing wing mechanism, using smart materials made of shape memory alloy (SMA) as actuators. After a presentation of the hybrid controller architecture that was adopted in the Part 1, this paper focuses on its implementation, simulation and validation.

The PID on-off controller was numerically and experimentally implemented using the Matlab/Simulink software. Following preliminary numerical simulations which were conducted to tune the controller, an experimental validation was performed. To implement the controller on the physical model, two programmable switching power supplies (AMREL SPS100-33) and a Quanser Q8 data acquisition card were used. The data acquisition inputs were two signals from linear variable differential transformer potentiometers, indicating the positions of the actuators, and six signals from thermocouples installed on the SMA wires. The acquisition board’s output channels were used to control power supplies in order to obtain the desired skin deflections. The experimental validation utilised an experimental bench test in laboratory conditions in the absence of aerodynamic forces, and a wind-tunnel test for different actuation commands. Simultaneously, the optimised aerofoils were experimentally validated with the theoretically-determined aerofoils obtained earlier. Both the transition point real time position detection and visualisation were realised in wind tunnel tests.

A computational study was performed to compare the stress distributions in finite element torsion box models of a box wing structure that result from employing four different wing/end fin joint fixities. All considered wings were trimmed in pitch. The joint fixities refer to the type of attachment that connects the tip of the fore and aft wings to the end fin. Using loads from a vortex lattice tool, the analysis determined the best wing-joint fixity of a statically loaded idealised box wing configuration by comparing the stress distributions resulting from the different wing joints in addition to other essential aerodynamic requirements. Analysis of the wing joint fixity indicates that the rigid joint is the most suitable.

Experimental aerodynamic testing of objects in close ground proximity at high subsonic Mach numbers is difficult due to the construction of a transonic moving ground being largely unfeasible. Two simple, passive methods have been evaluated for their suitability for such testing in a small blowdown wind tunnel: an elevated ground plane, and a symmetry (or mirror-image) approach. The methods were examined using an unswept wing of RAE2822 section, with experiments and Reynolds-Averaged Navier Stokes CFD used synergistically to determine the relative merits of the techniques. The symmetry method was found to be a superior approximation of a moving ground in all cases, with mild discrepancies observed only at the lowest ground clearance. The elevated ground plane was generally found to influence the oncoming flow and distort the flowfield between the wing and ground, such that the method provided a less-satisfactory match to moving ground simulations compared to the symmetry technique.