Search results

1 – 10 of 368
To view the access options for this content please click here
Article
Publication date: 4 October 2021

Abderrahim Serrar, Mohamed El Khlifi and Azeddine Kourta

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…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Originality/value

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.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0961-5539

Keywords

To view the access options for this content please click here
Article
Publication date: 1 August 1967

D.E. Wheatley

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…

Abstract

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.

Details

Aircraft Engineering and Aerospace Technology, vol. 39 no. 8
Type: Research Article
ISSN: 0002-2667

To view the access options for this content please click here
Article
Publication date: 1 June 1973

Michael Wright

Fluidics has become a bit of a dirty word among a lot of engineers; I try to avoid using it.’ The words don't sound like those of an engineer confident in his chosen…

Abstract

Fluidics has become a bit of a dirty word among a lot of engineers; I try to avoid using it.’ The words don't sound like those of an engineer confident in his chosen field, but they reflect a feeling that's pretty widespread in the world of fluidics—or, to use the term this par‐ticular engineer would prefer, fluid logic.

Details

Industrial Management, vol. 73 no. 6
Type: Research Article
ISSN: 0007-6929

To view the access options for this content please click here
Article
Publication date: 1 December 2005

A. Nakayama, F. Kuwahara and Y. Kamiya

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…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Originality/value

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.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 15 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

To view the access options for this content please click here
Article
Publication date: 2 July 2018

Darko Belavic, Andraž Bradeško and Hana Uršič

The purpose of this study is to design, fabricate and investigate low-temperature co-fired ceramic (LTCC) structures with integrated microfluidic elements. Special…

Abstract

Purpose

The purpose of this study is to design, fabricate and investigate low-temperature co-fired ceramic (LTCC) structures with integrated microfluidic elements. Special attention is paid to the study of fluid properties of micro-channels and microvalves, which are important constitutive parts of both, microfluidic systems and individual microfluidic devices.

Design/methodology/approach

Several test patterns of fluid channels with different geometry and different types of valves were designed and realized in LTCC technology. All test structures were tested under the flow of two fluids (liquids): water and isopropyl alcohol. Flow rates at different applied pressure were measured and hydrodynamic resistance and diode effect were calculated.

Findings

The investigation of the channels showed that viscosity of fluidic media has significant influence on the hydrodynamic resistance in channels with rectangular cross-section, while this effect is small on channels with square cross-section. The viscosity also has a decisive influence on the diode effect of different shape of valves, and therefore, it is important in the selection of the valve in practical applications.

Research limitations/implications

In this work, the investigation of hydrodynamic resistance of channels and diode effect of passive valves is limited on selected geometry and only on two fluidic media and two applied pressures. All these and some other parameters have a significant influence on fluidic properties, but this will be the topic of the next research work, which will be supported by numerical modelling.

Practical implications

The presented results are useful in the future designing process of LTCC-based microfluidic devices and systems.

Originality/value

Microfluidic in the LTCC structures is an unconventional use of this technology. Therefore, the fluid properties are relatively unsearched. On the other hand, the global use of microfluidic devices and systems is growing rapidly in various applications. They are mostly made by polymer materials, however, in more demanding applications; ceramic is a useful alternative.

Details

Microelectronics International, vol. 35 no. 3
Type: Research Article
ISSN: 1356-5362

Keywords

To view the access options for this content please click here
Article
Publication date: 1 January 1995

H. Oberhem and H.A. Nour Eldin

Modelling, computation and performance animation of turbomachinerysystems has recently enjoyed remarkable attention in CAD research. This isalso reflected its application…

Abstract

Modelling, computation and performance animation of turbomachinery systems has recently enjoyed remarkable attention in CAD research. This is also reflected its application to exhaust machine components such as turbo loaders and the exceptionally novel pressure wave machine (Comprex) in the automobile industry and gas turbines. The necessity for the thermo‐fluidic performance animation of such pressure wave machines results from the fact that the machine geometry must be adapted to the technical and thermo‐fluidic properties of the exhaust flow of the gas turbine or automobile engine. Experimental adaptation or adjustment is costly and should be validated for every application case. Thus the potential to apply accurate animation for such shock‐tube like behaviour of compressible flow is now economically promising with a view to optimizing the design of the pressure wave machine. This paper presents briefly the problem oriented algorithms used and illustrates the performance animation of the pressure wave machine operating under constant speed drive. After introducing the pressure wave machine operation, the principles and summary of the algorithms used to compute the thermodynamic behaviour within the cell, the boundary models and the accuracy of computation. A Comprex cycle operating on an engine exhaust gas with T = 920°K, p = 2bar is illustrated through 3‐dimensional representations for pressure, speed of flow and temperature. The particle path (gas and air) together with time representation of the state variables at different points of the Compex will be shown. The mass balance problem is discussed and the conditions for mass balanced flow for the gas as well as for the air side are given. The results achieved for such materially balanced pressure wave machines indicate a reduction in the costs for subsequent experimental validation and to deliver the sound base for further development towards considering the pre‐balanced transient operation cases as well.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 5 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

To view the access options for this content please click here
Article
Publication date: 18 October 2018

Yang Tingting, Li Aijun, Muhammad Taimoor and Rooh ul Amin

The purpose of this paper is to propose a high angle of attack short landing model for switched polytopic systems as well as to derive an equation for fluidic thrust…

Abstract

Purpose

The purpose of this paper is to propose a high angle of attack short landing model for switched polytopic systems as well as to derive an equation for fluidic thrust vector deflection angle based on pressure to reduce the velocity during the landing phase of flight.

Design/methodology/approach

In this paper, robust control algorithm is proposed for a non-linear high angle of attack aircraft under the effects of non-linearities, tottering hysteresis, irregular and wing rock atmosphere. High angle of attack short landing flight under asynchronous switching is attained by using the robust controller method. Lyapunov function and the average dwell time scheme is used for obtaining the switched polytopic scheme. The asynchronous switching and loss of data are controlled asymptotically. The velocity of aircraft has been lucratively reduced during the landing phase of flight by using the robust controller technique.

Findings

The proposed algorithm based on robust controller including the effects of non-linearities guarantee the successful reduction of velocity for high angle of attack switched polytopic systems.

Practical implications

As the landing phase of an aircraft is one of the complicated stage, this algorithm plays a vital role in stable and short landing under the condition of high angle of attack (AOA).

Originality/value

In this paper, not only the velocity of flight has been reduced, but also the high angle of attack has been attained during the landing phase, because of which the duration of landing has been reduced as well, while in most of the previous research, it is based on low angle of attack and long landing duration.

Details

Aircraft Engineering and Aerospace Technology, vol. 91 no. 1
Type: Research Article
ISSN: 1748-8842

Keywords

To view the access options for this content please click here
Article
Publication date: 1 June 1974

Goran Lundstrom

With the word fluid we mean gases and liquids. With a fluid control system we mean a control system in which we use a fluid as the signal carrier. Those fluid control…

Abstract

With the word fluid we mean gases and liquids. With a fluid control system we mean a control system in which we use a fluid as the signal carrier. Those fluid control systems in which the fluid is not air or oil are few, at least in connection with industrial robots (IRb).

Details

Industrial Robot: An International Journal, vol. 1 no. 6
Type: Research Article
ISSN: 0143-991X

To view the access options for this content please click here
Article
Publication date: 4 September 2017

Philipp Schloesser, Michael Meyer, Martin Schueller, Perez Weigel and Matthias Bauer

The area behind the engine/wing junction of conventional civil aircraft configurations with underwing-mounted turbofans is susceptible to local flow separation at high…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Originality/value

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

Details

Aircraft Engineering and Aerospace Technology, vol. 89 no. 5
Type: Research Article
ISSN: 1748-8842

Keywords

To view the access options for this content please click here
Article
Publication date: 8 June 2015

Mica Grujicic, Ramin Yavari, Jennifer Snipes and S Ramaswami

In the present work, a new blast-/ballistic-impact mitigation concept is introduced and its efficacy analyzed using advanced computational methods and tools. The concept…

Abstract

Purpose

In the present work, a new blast-/ballistic-impact mitigation concept is introduced and its efficacy analyzed using advanced computational methods and tools. The concept involves the use of a zeolite protective layer separated by air from the structure being protected and in contact with a water layer in front. The paper aims to discuss these issues.

Design/methodology/approach

To properly capture the attendant nano-fluidics phenomena, all the calculations carried out in the present work involved the use of all-atom molecular-level equilibrium and non-equilibrium molecular-dynamics simulations.

Findings

Under high-rate loading, water molecules (treated as a nano-fluidic material) are forced to infiltrate zeolite nanopores wherein, due to complex interactions between the hydrophobic nanopore walls and the hydrogen bonds of the water molecules, water undergoes an ordering-type phase transition and acquires high density, while a significant portion of the kinetic energy of the water molecules is converted to potential energy. Concomitantly, a considerable portion of this kinetic energy is dissipated in the form of heat. As a result of these energy conversion/dissipation processes, the (conserved) linear momentum is transferred to the target structure over a longer time period, while the peak loading experienced by the structure is substantially reduced.

Originality/value

To the authors’ knowledge, the present work constitutes the first reported attempt to utilize pure SiO2 hydrophobic zeolites in blast-/ballistic-impact protection applications.

Details

International Journal of Structural Integrity, vol. 6 no. 3
Type: Research Article
ISSN: 1757-9864

Keywords

1 – 10 of 368