State-of-the-art in aerodynamic shape optimisation methods

Aerodynamic optimisation has become an indispensable component for any aerodynamic design over the past 60 years, with applications to aircraft, cars, trains, bridges, wind turbines, internal pipe flows, and cavities, among others, and is thus relevant in many facets of technology. With advancements in computational power, automated design optimisation procedures have become more competent, however, there is an ambiguity and bias throughout the literature with regards to relative performance of optimisation architectures and employed algorithms. This paper provides a well-balanced critical review of the dominant optimisation approaches that have been integrated with aerodynamic theory for the purpose of shape optimisation. A total of 229 papers, published in more than 120 journals and conference proceedings, have been classified into 6 different optimisation algorithm approaches. The material cited includes some of the most well-established authors and publications in the field of aerodynamic optimisation. This paper aims to eliminate bias toward certain algorithms by analysing the limitations, drawbacks, and the benefits of the most utilised optimisation approaches. This review provides comprehensive but straightforward insight for non-specialists and reference detailing the current state for specialist practitioners

Semi-span wind tunnel testing without conventional peniche

Low-speed wind tunnel tests of a flexible wing semi-span model have been implemented in the 9×79×7 ft de Havilland wind tunnel at the University of Glasgow. The main objective of this investigation is to quantify the effect of removing the traditional peniche boundary layer spacer utilised in this type of testing. Removal of the peniche results in a stand-off gap between the wind tunnel wall and the model’s symmetry plane. This offers the advantage of preventing the development of a horseshoe vortex in front of the model, at the peniche/wall juncture. The formation of the horseshoe vortex is known to influence the flow structures around the entire model and thus alters the model’s aerodynamic behaviours. To determine the influence of the stand-off gap, several gap heights have been tested for a range of angles of attack at Re=1.5×106Re=1.5×106 , based on the wing mean aerodynamic chord (MAC). Force platform data have been used to evaluate aerodynamic coefficients, and how they vary with stand-off heights. Stereoscopic Particle Imaging Velocimetry (sPIV) was used to examine the interaction between the tunnel boundary layer and model’s respective stand-off gap. In addition, clay and tuft surface visualisation enhanced the understanding of how local flow structures over the length of the fuselage vary with stand-off height and angle of attack. The presented results show that a stand-off gap of four-to-five times the displacement thickness of the tunnel wall boundary layer is capable of achieving a flow field around the model fuselage that is representative of what would be expected for an equivalent full-span model in free-air—this cannot be achieved with the application of a peniche

Experimental investigation on shock wave diffraction over sharp and curved splitters

Shock wave diffraction occurs when a normal travelling wave passes through a sudden area expansion. Turbulent, compressible, and vortical are the characterising adjectives that describe the flow features, which are slowly smeared out due to the dissipative nature of turbulence. The study of this phenomenon provides insight into several flow structures such as shear layer formation, vortex development, and vortex/shock interaction whose applications include noise control, propulsion or wing aerodynamics. A large amount of research has been carried out in the analysis of shock wave diffraction mainly around sharp wedges, but only few studies have considered rounded corners. This project has the aim to examine and compare the flow features which develop around three different geometries, ramp, symmetric and rounded, with experimental incident shock Mach numbers of 1.31 and 1.59, and Reynolds numbers of 1.08×106 and 1.68×106. Schlieren photography is used to obtain qualitative information about the evolution of the flow field. The results show that ramp and symmetrical wedges with a tip angle of 172° behave in the same manner, which exhibit clear dissimilarities with a curved corner. The flow field evolves more rapidly for a higher incoming Mach number which is also responsible for the development of stronger structures

Aerodynamic and Stability Optimisation of Non-Planar Wings

No abstract available

Electrohydrodynamic Methods for Fluid Flow Control

No abstract available

Pseudo-shock waves and their interactions in high-speed intakes

In an air-breathing engine the flow deceleration from supersonic to subsonic conditions takes places inside the isolator through a gradual compression consisting of a series of shock waves. The wave system, referred to as a pseudo-shock wave or shock train, establishes the combustion chamber entrance conditions, and therefore influences the performance of the entire propulsion system. The characteristics of the pseudo-shock depend on a number of variables which make this flow phenomenon particularly challenging to be analysed. Difficulties in experimentally obtaining accurate flow quantities at high speeds and discrepancies of numerical approaches with measured data have been readily reported. Understanding the flow physics in the presence of the interaction of numerous shock waves with the boundary layer in internal flows is essential to developing methods and control strategies. To counteract the negative effects of shock wave/boundary layer interactions, which are responsible for the engine unstart process, multiple flow control methodologies have been proposed. Improved analytical models, advanced experimental methodologies and numerical simulations have allowed a more in-depth analysis of the flow physics. The present paper aims to bring together the main results, on the shock train structure and its associated phenomena inside isolators, studied using the aforementioned tools. Several promising flow control techniques that have more recently been applied to manipulate the shock wave/boundary layer interaction are also examined in this review

Experimental Study of Low-Speed Cavity Flow Using Steady Jets

Open cavity ሺܮ/ܦ = 4ሻ was examined at low speed ሺܷஶ = 26 ݉/ݏሻ. The baseline flow showed a typical open cavity flow. It was also found that a region of relatively high velocity fluctuations (indicated by RMS values) extends along the cavity separated shear layer from the mid of the cavity to the cavity’s trailing edge. Steady jets at an outlet velocity of 1.8 m/s was forced through a narrow slot at the leading edge. The jets modified the profile shape of the averaged ܷ velocity for the shear layer at the close proximity of the leading edge. However, the jet increased the fluctuation in the separated shear layer

Control of flow separation on a contour bump by jets in a Mach 1.9 free-stream: an experimental study

Flow separation control over a three-dimensional contour bump using jet in a Mach 1.9 supersonic free-stream has been experimentally investigated using a transonic/supersonic wind tunnel. Jet total pressure in the range of 0–4 bar was blowing at the valley of the contour bump. Schlieren photography, surface oil flow visualisation and particle image velocimetry measurements were employed for flow visualisation and diagnostics. Experimental results show that blowing jet at the valley of the contour bump can hinder the formation and distort the spanwise vortices. The blowing jet can also reduce the extent of flow separation appears downstream of the bump crest. It was observed that this approach of flow control is more effective when high jet total pressure is employed. It is believed that a pressure gradient is generated as a result of the interaction between the flow downstream of the bump crest and the jet induced shock leads to the downwards flow motion around the bump valley

Aerodynamic and Stability Optimisation of Non-Planar Wings

No abstract available

Coupling Reading Strategies and Literary Texts: An Approach to Improving Reading

The present study aimed to explore the effect of reading comprehension strategy use and literature on the improvement of the reading ability of Iranian EFL learners. An analysis of the use of SQR3 (survey, question, read, recite, and review) and TPS (think, pair, and share) comprehension strategies in terms of the learners’ reading achievements was perused. Moreover, the differences between the reading of short stories as the source of teaching reading and adapted books were studied. The data were collected through a pretest-treatment-posttest design and were analyzed using t-tests and ANOVA. Results revealed that SQR3 and TPS groups outperformed the learners who did not receive any treatment. This indicated that merging reading strategies in reading short stores significantly improved the learners’ comprehension level. The study suggests that instructors should be aware of the learning opportunities that arise in literature-centered readings, provide learners with and instruct comprehension strategies, and accordingly enhance the experience of reading in a foreign language