Ice accretions can significantly change the aerodynamic performance of wings and rotor blades. Significant performance degradation can occur when ice accreations cause regions of separated flow, to predict this change implies, at a minimum, the solution of the Reynolds-Averaged Navier-Stokes equations. This paper presents validation for two generic cases involving the flow over aerofoil sections with added synthetic ice shapes. Results were obtained for two aerofoils, namely the NACA 23012 and a generic multi-element configuration. These results are compared with force and pressure coefficient measurements obtained in the NASA LTPT wind-tunnel for the NACA 23012, and force, PIV and boundary-layer measurements obtained at DNW for the multi-element case. The level of agreement is assessed in the context of industrial requirements.

This paper presents the concept of using cylindrical pins as short protuberances for trajectory control of a blunted cone in the supersonic and hypersonic regimes. Supersonic and hypersonic flow interactions for cylindrical protuberances, installed on a blunt cone are studied for their aerodynamic effects. The utility of these protuberances for aerodynamic control and trajectory shaping of a re-entry cone are explored. Static aerodynamic coefficients in the Mach range of 2–9·7 at various incidences are computed. The pressure distribution along the vehicle longitudinal axis in the presence of the pin-protuberance is studied using CFD analysis. With the altered pressure distribution, a net increase in the aerodynamic force is obtained which can be actively utilised for flight control and maneuvering of the vehicle during re-entry. After quantifying the aerodynamic effects of the protuberance, it is modelled and used as an effective actuation mechanism for flight feedback control. It is shown that this can work as an effective control device for Mach numbers less than five. An actuator design for insertion/retraction of the protuberance is presented and modelled, and a robust controller is synthesised which can in real time govern the position of the protuberance to control the flight attitude angle to achieve a desired trajectory. The controller takes in measurements of the vehicle’s pitch angle and actuates the pin height continuously to control the pitch angle to a desired value. The control performance is demonstrated on a high fidelity six degrees-of-freedom (6-DOF) nonlinear flight simulation.

This paper investigates the feasibility of flutter control using resistively shunted piezoceramics. 2D aerofoil model is elastically restrained in heave and pitch by a set of leaf springs modeled as Bernoulli-Euler beams. The piezoceramic transducers are bonded to the leaf springs. Unsteady aerodynamic theory is used to solve the flutter determinant incorporating the additive damping terms due to resistive shunting. Tuned dampers realised by resistive shunted piezoceramics in heave and pitch springs could enhance flutter speed in the range 25-50 % based on additive damping of 10 % achieved due to resistive shunting of piezoceramics in either pitch spring, heave spring or both.

In an effort to reduce the negative impact of civil aviation on the human environment, trajectory optimisation techniques have been used to minimise the single event impact of noise and gaseous emissions of departures on communities in the vicinity of airports. For this purpose, the earlier developed trajectory optimisation tool NOISHHH has been adapted to design departure trajectories optimised for environmental criteria, based on area navigation. The new version of NOISHHH combines a noise model, an emissions inventory model, a geographic information system and a dynamic trajectory optimisation algorithm to generate flight paths with minimised environmental impact. Operational constraints have been introduced to ensure that the resulting flight paths are fully compliant with the guidelines and regulations that apply to the design of standard instrument departures and the use of area navigation. To illustrate the capabilities of the new version of NOISHHH, two numerical examples are presented, which are both redesigns of standard instrument departures currently in use at Amsterdam Airport Schiphol.

Accurate stress and strain analysis in bolted joints is of considerable interest in order to design more efficient and safer aerospace structural elements. In this paper, a finite element modelling of aluminium alloy 7075-T6 bolted plates, which are extensively used in aircraft structures, is discussed. The ANSYS Finite Element (FE) package was used for modelling the joint and estimating the stresses and strains created in the joint due to initial clamping forces and subsequent longitudinal tensile loadings. A double-lap bolted joint with a single bolt and nut was considered in the study. A three-dimensional (3D) finite element model of the joint was generated, and then subjected to three different simulated clamping forces followed by different levels of longitudinal tensile load. 3D surface-to-surface contact elements were employed to model the contact between the various components of the bolted joint. Friction effects were considered in the numerical analysis; and moreover, the clearance between the bolt and the plates was simulated in the model. FE results revealed beneficial compressive stresses near the hole edge as a result of applying the clamping. It was found that a higher clamping force can significantly decrease the magnitude of the resultant tensile stress at the hole edge and also bearing stress in the joint when subjected to the longitudinal tensile load.

The design of a 6U CubeSat including spacecraft systems and imaging payload is described for an Earth observation mission. From a Sun synchronous orbit at an altitude of 600km the design enables imaging with a 6.5m GSD, an optical MTF (on axis) of >59% at half Nyquist and >35% at Nyquist, a 26km swath, 12 bit digitisation and SNR of 120-200:one in five spectral bands; blue, green, red, red edge and near infrared. Data can be downlinked at the rate of 14 Mbps to a 3.7m S band ground station. This design allows an 8kg CubeSat to perform Earth observation missions equivalent to those of current 50-150kg microsatellites, with a corresponding reduction in cost.

A series of tests were carried out to study the unsteady wake behaviour behind an aerofoil which is a section of a wind-turbine blade. The model is oscillated in pitch about its quarter chord axis at various reduced frequencies, amplitudes, and mean angles-of-attack. Instantaneous and mean velocity profiles were obtained using total and static pressure at 35 vertically aligned points behind the aerofoil via two similar rakes. The rakes were located at a distance of 1·5 chord length behind the model. An estimation of the real time and average variations of the linear momentum deficit during the oscillation cycle is obtained and has been compared with the corresponding static data. The results show that oscillation amplitude and reduced frequency have pronounced effects on the wake characteristics.

The unsteady flowfield of a series of mixed-compression hypersonic inlets with different bleeding rates were numerically simulated. Firstly unstart oscillatory flow of hypersonic inlets caused by downstream massflow choking was discussed. Then the effects of boundary layer bleeding on the averaged performance parameter of hypersonic inlets, and on the dominant amplitude and frequency of unstart oscillatory flow of hypersonic inlets were presented. The reasons why the boundary-layer bleeding can suppress unstart oscillatory flow of hypersonic inlets were analysed. In conclusion, the averaged performance parameter of hypersonic inlets during a big buzz is improved greatly, and the dominant frequency of unstart oscillatory flow of hypersonic inlets is reduced in contrast with no bleeding, and all these are benefit to the design and operation of hypersonic inlets.

The climate impacts of three fleets of supersonic small-scale transport aircraft (S4TA) are simulated. Based on characteristic aircraft parameters, which were developed within the EU-project HISAC, emissions along geographically representative trajectories are calculated and in addition the resulting changes in the atmospheric composition (carbon dioxide, ozone layer, water vapour) and climate (near surface global mean temperature) are deduced. We assume a fleet development with an entry in service in 2015, a full fleet in 2050. The results show a temperature increase of 0·08mK (0·07-0·10mK) with only small but statistically significant variations between the configurations, leading to a minimum climate impact for a weight optimised and hence lower flying aircraft. A climate impact ratio of 3·0 ± 0·4 between a S4TA and its subsonic counterpart is calculated, which is considerable less than for previous supersonic fleets because of a lower flight altitude, leading to smaller water vapour impacts.

The ground vortices generated by an intake under both headwind and crosswind configurations have been investigated using computational and experimental approaches. The flow field of a scale-model intake was experimentally studied using stereoscopic particle image velocimetry to measure the ground vortex in conjunction with induct total pressure measurements for the internal flow. The computational predictions were performed using an unsteady Reynolds averaged Navier-Stokes approach. The experimental results show that under crosswind conditions a single ground vortex forms which becomes stronger as the crossflow velocity is increased. Under headwind conditions the measured ground vortex strength initially increases with freestream velocity before it reaches a local maximum and then reduces thereafter. The computations also exhibit the same characteristics and show good agreement with the measurements for some configurations. Based on the predictions, the complex flow field topology is investigated and a detailed flow model of the vortex flow field under crosswind conditions is proposed.

Intelligent shape optimisation architecture is developed, validated and applied in the design of high-altitude long endurance aerofoil (HALE). The direct numeric optimisation (DNO) approach integrating a geometrical shape parameterisation model coupled to a validated flow solver and a population based search algorithm are applied in the design process. The merit of the DNO methodology is measured by computational time efficiency and feasibility of the optimal solution. Gradient based optimisers are not suitable for multi-modal solution topologies. Thus, a novel particle swarm optimiser with adaptive mutation (AM-PSO) is developed. The effect of applying the PARSEC and a modified variant of the original function, as a shape parameterisation model on the global optimal is verified. Optimisation efficiency is addressed by mapping the solution topology for HALE aerofoil designs and by computing the sensitivity of aerofoil shape variables on the objective function. Variables with minimal influence are identified and eliminated from shape optimisation simulations. Variable elimination has a negligible effect on the aerodynamics of the global optima, with a significant reduction in design iterations to convergence. A novel data-mining technique is further applied to verify the accuracy of the AM-PSO solutions. The post-processing analysis, to swarm optimisation solutions, indicates a hybrid optimisation methodology with the integration of global and local gradient based search methods, yields a true optima. The findings are consistent for single and multi-point designs.

The paper begins with a summary of the performance characteristics of the most important classes of adaptive aerostructures which are relevant for UAVs and the materials which drive them. The paper describes several classes of UAVs that take advantage of the various kinds of adaptive aerostructures technologies. These technologies are shown to be suitable for very small and even hard-launched UAVs, hovering, high speed, low speed and convertible UAVs (i.e. UAVs that can transition between helicopter and aircraft/missile flight modes). The first class of UAVs presented highlights newly invented post-buckled precompressed (PBP) actuators which are particularly well suited to enhancing convertible coleopters or ‘ultra-high performance UAVs.’ These UAVs are capable of hovering for extended periods of time as a helicopter in gusty, windy, dusty, real tactical environments, then popping up, converting and dashing out like a missile at several hundred knots. The paper shows photos (i.e. no computer simulations) of convertible coleopter launches from armoured vehicles, a battle-damage assessment exercise and a live fire sequence with 40mm munitions. The paper concludes with a description of the visual signature suppression (VSS) system which was employed on a 2m UAV. The VSS system was shown to suppress the visual cross section to below 1·8cm2 which is the threshold for human aircraft observation. Accordingly, VSS equipped aircraft are said to ‘disappear’ in mid flight.

This paper studies hovering capability of flapping two-dimensional tandem wing sections inspired by a real dragonfly wing configuration and kinematics. Based on unsteady numerical simulations, the dragonfly corrugated wings have been benchmarked against a flat wing in terms of the aerodynamic forces and flow structures generated during a flapping cycle. The timing of rotation at each stroke is studied by pitch rotation at three different rates, i.e., 80%, 60% and 40% of a flapping period. The results suggest that the longer time pitch rotation with the period of 80% of the overall flapping period is closer to the force calculations obtained of a balanced flight, that is, the mean vertical force supports the dragonfly weight of 0.754 g with a small difference of 0.92% and the mean horizontal force indicates negligible thrust. However, the corrugated wing performs aerodynamically differently from the flat plate with differences in and in by ±2.06% for the corrugated shape. The vorticity flow field for both wings have been recorded at some instants of flapping motions which give more explanation of such dissimilarity.

Minimisation of airframe mass reduces the costs of materials and manufacturing, as well as fuel consumption and atmospheric emissions. Fast, reliable analysis tools are required during preliminary design, when many alternative configurations and load cases are considered. The modelling and computational costs of finite element analysis are avoided by employing exact strip solutions of the governing differential equations, using the Wittrick-Williams algorithm to solve the resulting transcendental eigenproblems of buckling and vibration. This paper reviews recent enhancements to the exact strip method for analysis and optimum design of aerospace structures, using the specialist software VICONOPT. Lighter composite panels can be designed by obtaining reliable estimates of the reduced postbuckling stiffnesses when loaded in compression and shear. Further advances include discrete optimisation of layer thicknesses to allow for practical composite manufacturing constraints, vibration constraints, and a newly extended multi-level interface combining finite element analysis of a whole wing with exact strip postbuckling design of individual panels.

Knowledge is a vital component of engineering design. Computer systems enriched with logic and engineering knowledge can support engineering design by automating repetitive and time-consuming processes. This automation is enabled using knowledge based engineering (KBE) techniques and can be obtained using dedicated KBE systems or augmented CAD systems, already pervasive throughout engineering industry. The development of these KBE applications is supported by a six-phase development process ranging from engineering process analysis to software development to business implementation. Distinctions and similarities exploiting alternative KBE platforms are addressed for each phase of the development process. An example KBE application is discussed, supporting the design of laminate aircraft fuselage panels. The implementation of the application is emphasised and five key-aspects required for a successful implementation are defined.

Fitting a spike on a blunt body provides a drag reduction at supersonic and hypersonic speeds. In this study, the laminar flow over a spiked, conical body terminated by a spherical cap, inspired by the Apollo re-entry capsule design, was investigated using a hypersonic wind tunnel. Schlieren pictures revealed the absence of flow unsteadiness for the range of spike lengths tested, and force measurements showed a maximum reduction of 77% of the unspiked body drag.

A simple theoretical model based on the pressure drag generated by a solid cone showed good agreement with the experimental data. The measured shock stand-off distance agreed well with predictions.

This paper summarises recent research conducted at the Defence Science and Technology Organisation in the area of aircraft battle damage repair, covering aspects such as ballistic testing, ballistic damage prediction, non-destructive damage inspection, structure residual-strength assessment, repair materials and techniques, repair design approaches, repair implementation and demonstration. The research has been focused on military helicopter composite structures. This paper provides an overview of a wide range of research conducted and detailed information in selected areas. Considerations for future research directions are also briefly discussed.

Mitigation of climate change is a challenge to science and society. Here, we establish a methodology, applicable in multi-disciplinary optimisation (MDO) during aircraft pre-design, allowing a minimisation of the aircraft’s potential climate impact. In this first step we consider supersonic aircraft flying at a cruise altitude between 45kfeet (~13·5km, 150hPa) and 67kfeet (~20·5km, 50hPa). The methodology is based on climate functions, which give a relationship between 4 parameters representing an aircraft/engine configuration and an expected impact on global mean near surface temperature as an indicator for the impact on climate via changes in the greenhouse gases carbon dioxide, water vapour, ozone and methane. These input parameters are cruise altitude pressure, fuel consumption, fuel flow and Mach number. The climate functions for water vapour and carbon dioxide are independent from the chosen engine, whereas the climate functions for ozone and methane depend on engine parameters describing the nitrogen oxide emissions. Ten engine configurations are taken into account, which were considered in the framework of the EU-project HISAC. An analysis of the reliability of the climate functions with respect to the simplified climate-chemistry model AirClim and a detailed analysis of the climate functions is given.

Ultrasonic guided wave techniques have great potential for structural health monitoring applications. Appropriate mode and frequency selection is the basis for achieving optimised damage monitoring performance. In this paper, several important guided wave mode attributes are introduced in addition to the commonly used phase velocity and group velocity dispersion curves while using the general corrosion problem as an example. We first derive a simple and generic wave excitability function based on the theory of normal mode expansion and the reciprocity theorem. A sensitivity dispersion curve is formulated based on the group velocity dispersion curve. Both excitability and sensitivity dispersion curves are verified with finite element simulations. Finally, a goodness dispersion curve concept is introduced to evaluate the tradeoffs between multiple mode selection objectives based on the wave velocity, excitability and sensitivity.