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The purpose of this study is to compare two unsteady actuators: an oscillator and a sweeping jet. Both actuators can produce an oscillating jet of different amplitudes and frequencies without any moving parts, making them an attractive actuator concept. The Coanda effect phenomenon can explain the operating principles of these two unsteady actuators.

A numerical study was conducted to compare the amplitudes and frequencies of fluidic and sweeping jet (SJ) oscillators to obtain an efficient actuator to control separated flows at high Reynolds numbers. For this goal, two-dimensional unsteady Reynolds-averaged Navier-Stokes simulations were carried out using computational fluid dynamics (CFD) fluent code to evaluate the actuator performances. The discrete fast Fourier transform method determined the oscillation frequencies.

The oscillation frequencies gradually increase as the inlet pressure increases. The characteristics and dimensions of the vortices produced in the mixing chamber and feedback loops vary overtime when the injected fluid is swept sideways. The frequencies supplied by the SJ are stronger than those obtained by the fluidic oscillator, which may contribute to improving the aerodynamic performance at a lower power supply cost.

The existence of the splitter in the fluidic oscillator led to the production of separate pulses, which would be useful in various industrial applications, including active control of combustion and mixing processes while other applications such as flow separation control require SJs. With the latter actuator higher and interesting frequencies can be obtained, leading to efficient flow control.

To introduce an efficient two‐dimensional numerical procedure for a three‐dimensional internal flow through a complex passage with a small depth, in which the viscous effects from upper and lower walls are significant.

A set of two‐dimensional governing equations has been derived by integrating the full three‐dimensional Navier‐Stokes equations over the depth. Then, this set of the governing equations has been discretized using a finite volume method. Simple algorithm and quick scheme are used to solve the resulting discretized equations.

A numerical experiment conducted to investigate the oscillation mechanism of a feedback fluidic oscillator reveals that the feedback passage plays an important role of transmitting the pressure rise to the control port, which triggers the jet stream to deflect towards the opposite side wall in the reaction region. Comparison of the prediction and experiment substantiates the validity of the present numerical procedure.

The two‐dimensional numerical procedure, proposed in this study, will be used by researchers and practitioners to investigate various kinds of complex passages with a small depth. Especially, those who are interested in fluidic devices may find it extremely convenient to conduct numerical experiments.

The area behind the engine/wing junction of conventional civil aircraft configurations with underwing-mounted turbofans is susceptible to local flow separation at high angles of attack, which potentially impacts maximum lift performance of the aircraft. This paper aims to present the design, testing and optimization of two distinct systems of fluidic actuation dedicated to reduce separation at the engine/wing junction.

Active flow control applied at the unprotected leading edge inboard of the engine pylon has shown considerable potential to alleviate or even eliminate local flow separation, and consequently regain maximum lift performance. Two actuator systems, pulsed jet actuators with and without net mass flux, are tested and optimized with respect to an upcoming large-scale wind tunnel test to assess the effect of active flow control on the flow behavior. The requirements and parameters of the flow control hardware are set by numerical simulations of project partners.

The results of ground test show that full modulation of the jets of the non-zero mass flux actuator is achieved. In addition, it could be shown that the required parameters can be satisfied at design mass flow, and that pressure levels are within bounds. Furthermore, a new generation of zero-net mass flux actuators with improved performance is presented and described. This flow control system includes the actuator devices, their integration, as well as the drive and control electronics system that is used to drive groups of actuators.

The originality is given by the application of the two flow control systems in a scheduled large-scale wind tunnel test.

This paper aims to provide an insight into robot developments that use bioinspired design concepts.

Following a short introduction to biomimetics, this paper first provides examples of bioinspired terrestrial, aerial and underwater robot navigation techniques. It then discusses bioinspired locomotion and considers a selection of robotic products and developments inspired by snakes, bats, diving birds, fish and dragonflies. Finally, brief concluding comments are drawn.

The application of design concepts that mimic the capabilities and processes found in living creatures can impart robots with unique abilities. Bioinspired techniques used by insects and other organisms, notably optic flow and sunlight polarisation sensing, allow robots to navigate without the need for methods such as simultaneous localisation and mapping, GPS or inertial measurement units. Bioinspired locomotion techniques have yielded robots capable of operating in water, air and on land and in some cases, making the transition between different media.

This shows how bioinspired design concepts can impart robots with innovative and enhanced navigation and locomotion capabilities.

This study aims to achieve optimum flow separation control for a road vehicle using a reverse flow fan on rear side.

A full-length reverse flow fan array (fan’s air speed is 50% of the car’s speed) is attached throughout the width of the vehicle at rear edge corner.

The reverse flow fan array positioned at rear edge of car pushes the airflow against the car’s rear window. It creates the recirculation region and alters the pressure distribution. This reduces the lift coefficient by 150%, which becomes the downforce and reduces the drag coefficient by 22%. As the car speed increases, fan speed should also be increased for effective flow control.

This active flow control method for 3D Ahmed car body has been studied computationally at low speed (40 m/s).

This design increases the downforce, thus gives better cornering speed and stability, and decreases the drag which improves fuel efficiency. It can be used for effective flow control of cars (hatchback/sedan). The findings can be applied to the bluff bodies, road vehicles, UAV and helicopter fuselage for flow separation control.

The fan array is attached on car’s rear side, which blows air against the car’s rear window. It alters the pressure distribution and aerodynamics forces favorably. But the existing high-speed fan used in a sports cars sucks the air from bottom and pushes it rearward, which increases both the traction force and drag.

FLUIDICS is a term coined recently defining a rapidly emerging technology which involves the use of gaseous or liquid fluids in motion to perform functions such as amplification, sensing, switching, logic or computation. The accelerating interest in fluidics is no doubt due to the increasing awareness that fluid energy can be manipulated in much the same way as electricity and without moving parts. Also, since fluidic control components are highly reliable under extreme environmental conditions and are impervious to radiation — magnetic or nuclear—they offer many advantages for use in aerospace or nuclear engineering. These particular advantages and others, coupled with the probable low ultimate economic costs of fluidic components, are further stimulating active interest in many commercial and industrial applications.

The purpose of this paper is to provide a review of recent progress in self‐assembly technology, principally in the microelectronics context.

First, the paper discusses the application of nanoscale self‐assembly techniques to microelectronic and related components and then considers research involving larger devices.

The paper shows that a range of self‐assembly techniques is being used to fabricate both production and experimental microelectronic devices, often with the aim of developing alternatives to copper wire interconnects. Other, experimental self‐assembly techniques are being developed for the packaging and mounting of microelectronic components on substrates.

Provides a useful, detailed review of the use of self‐assembly techniques at the nanoscale, microscale and macroscale.

The purpose of this paper is to present numerical investigations of the flow dynamic characteristics of a 47° Ahmed Body to identify wake flow control strategy leading to drag coefficient reduction, which could be tested later on sport utility vehicles.

This study begins with a mean flow topology description owing to dynamic and spectral analysis of the aerodynamic tensor. Then, the sparse promoting dynamic modal decomposition method is discussed and compared to other modal approaches. This method is then applied on the wall and wake pressure to determine frequencies of the highest energy pressure modes and their transfers to other frequency modes. This analysis is then used to design appropriated feedback flow control strategies.

This dynamic modal decomposition highlights a reduced number of modes at low frequency which drive the flow dynamics. The authors especially notice that the pressure mode at a Strouhal number of 0.22, based on the width between feet, induces aerodynamic losses close to the rear end. Strategy of the proposed control loop enables to dampen the energy of this mode, but it has been transferred to lower frequency mode outside of the selected region of interest.

This analysis and methodology of feedback control shows potential drag reduction with appropriated modal energy transfer management.

The purpose of this paper is to investigate the mechanism and performance of a potential strategy, which is to enhance turbulence to carry out drag reduction for heavy trucks.

Enhancing turbulence deflector (ETD) was placed on the roof surface of an ground transportation system (GTS) to investigate the drag reduction mechanism of enhancing turbulence. Transition shear-stress transport improved delay detach eddy simulation model was adopted to simulate the unsteady small-scale flow around the ETD.

By optimizing the three influencing factors, diameter, streamwise length and streamwise position, the optimized ETD has achieved a maximum drag reduction of 7.04%. The analysis of flow field results shows that enhancing turbulence can effectively suppress flow separation and reduce the negative pressure intensity in the wake region of GTS.

The present work provides another potential possibility for the improvement of the aerodynamic performance of heavy trucks.

Accles & Pollock Ltd. of Oldbury, Worcestershire, a TI Steel Tube Division company, will be exhibiting a comprehensive range of precision steel tube and tubular products, including plain, annularly convoluted and thin wall tube, at Farnborough.