An Aerial Deployed Unmanned Autonomous Glider for Cross-Channel Flight

This paper describes the technical and operational challenges of the first cross-Channel flight performed by an unmanned autonomous glider. The glider chosen for the attempt was a quarter scale Slingsby Type 45 Swallow. It was found to have a lift-to-drag ratio of 8, as verified by wind tunnel force balance tests. Essential retrospective aerodynamic refinements to the design, including modifications of the wing root and tip sections and wing aspect ratio, were modelled analytically and found to increase the aircraft’s lift-to-drag ratio to 19. The launch mechanism devised for the modified glider featured a bespoke crate suspended under an airborne helicopter at an altitude of 10,000 ft, from which the aircraft was released from an internal recess. The glider was pre-programmed to fly autonomously via waypoint navigation and completed the 22 mile mission in less than one hour at an average ground speed of 27 knots, a sink rate of 3 ft/s and with 3,500 ft altitude to spare. The successful flight, which was filmed from onboard cameras and a chase helicopter, represents a unique first in autonomous aviation and is unofficially the longest straight distance flight for an unmanned engineless glider

Particle image velocimetry measurements of the interaction of synthetic jets with a zero-pressure gradient laminar boundary layer

Copyright @ 2010 American Institute of PhysicsAn experimental investigation of the interaction between a synthetic jet actuator and a zero-pressure gradient laminar boundary layer is reported. The aim of this study is to quantify the impact of synthetic jet vortical structures; namely, hairpin vortices, stretched vortex rings and tilted vortex rings on a boundary layer, and to assess their relative potential for flow separation control. Streamwise particle image velocimetry was employed in a water flume (free stream boundary layer thickness Reynolds number of 500 and boundary layer thickness-to-jet orifice diameter ratio of 4) to obtain phase- and time-averaged boundary layer profile information of the impact of synthetic jets near the wall. The potential for flow control was assessed by analyzing near wall fluid mixing, realized by the measure of increase in wall shear stress produced by a passing vortex. Hairpin vortices (produced at a jet-to-free stream velocity ratio, VR=0.32 and dimensionless stroke length, L=1.6) and stretched vortex rings (VR=0.27; L=2.7) exhibit characteristics akin to a streamwise vortex pair with a common upwash. Conversely, tilted vortex rings (VR=0.54; L=2.7) induce a streamwise vortex pair in the near wall region with a common downwash. Wall shear stress measurements show that synthetic jets composed of stretched vortex rings offer the best combination of near wall fluid mixing, persistency, and low rms fluctuations for potential applications of flow separation control.Financial support from the Engineering and Physical Sciences Research Council (EPSRC Grant No. AF566NEZ) was used for this work

Systems and certification issues for civil transport aircraft flow control systems

This article is placed here with permission from the Royal Aeronautical Society - Copyright @ 2009 Royal Aeronautical SocietyThe use of flow control (FC) technology on civil transport aircraft is seen as a potential means of providing a step change in aerodynamic performance in the 2020 time frame. There has been extensive research into the flow physics associated with FC. This paper focuses on developing an understanding of the costs and design drivers associated with the systems needed and certification. The research method adopted is based on three research strands: 1. Study of the historical development of other disruptive technologies for civil transport aircraft, 2. Analysis of the impact of legal and commercial requirements, and 3. Technological foresight based on technology trends for aircraft currently under development. Fly by wire and composite materials are identified as two historical examples of successful implementation of disruptive new technology. Both took decades to develop, and were initially developed for military markets. The most widely studied technology similar to FC is identified as laminar flow control. Despite more than six decades of research and arguably successful operational demonstration in the 1990s this has not been successfully transitioned to commercial products. Significant future challenges are identified in cost effective provision of the additional systems required for environmental protection and in service monitoring of FC systems particularly where multiple distributed actuators are envisaged. FC generated noise is also seen as a significant challenge. Additional complexity introduced by FC systems must also be balanced by the commercial imperative of dispatch reliability, which may impose more stringent constraints than legal (certification) requirements. It is proposed that a key driver for future successful application of FC is the likely availability of significant electrical power generation on 787 aircraft forwards. This increases the competitiveness of electrically driven FC systems compared with those using engine bleed air. At the current rate of progress it is unlikely FC will make a contribution to the next generation of single-aisle aircraft due to enter service in 2015. In the longer term, there needs to be significant movement across a broad range of systems technologies before the aerodynamic benefits of FC can be exploited.This work is supported by the EU FP6 AVERT (AerodynamicValidation of Emissions Reducing Technologies) project

The near wall effect of synthetic jets in a boundary layer

Copyright @ 2007 Elsevier Inc. All rights reserved.An experimental investigation to analyse the qualitative near wall effect of synthetic jets in a laminar boundary layer has been undertaken for the purpose of identifying the types of vortical structures likely to have delayed separation on a 2D circular cylinder model described in this paper. In the first instance, dye visualisation of the synthetic jet was facilitated in conjunction with a stereoscopic imaging system to provide a unique quasi three-dimensional identification of the vortical structures. Secondly, the impact of synthetic jet structures along the wall was analysed using a thermochromic liquid crystal-based convective heat transfer sensing system in which, liquid crystals change colour in response to the thermal footprints of a passing flow structure. Of the different vortical structures produced as a result of varying actuator operating and freestream conditions, the footprints of hairpin vortices and stretched vortex rings revealed a marked similarity with the oil flow pattern of a vortex pair interacting with the separation line on the cylinder hence suggesting that either of these structures was responsible in delaying separation. Conditions were established for the formation of the different synthetic jet structures in non-dimensional parameter space

Curculionidae (weevils) of the alpine zone of mount Kenya

Volume: XXVI

Distribution and host-specificity of a number of fleas collected in south and central Kenya

Volume: XXVI

Development of a smoke visualisation system for wind tunnel laboratory experiments

The design, build and test of a smoke visualisation system for a vertical wind tunnel at Brunel University are described. The smoke visualisation system utilised a fog machine for smoke generation and required the design and manufacture of a smoke rake to produce smoke lines inside the wind tunnel test section. The application of these smoke lines over several test objects, including wing sections and bluff body shapes, demonstrated the functionality of the smoke system in producing high-quality visualisations. The facility has proven to be an economic addition in supporting other research projects and is anticipated to be a valuable ‘hands on’ addition to existing aerospace laboratory teaching