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Aircraft noise is dominant for residents near airports when planes fly at low altitudes such as during departure and landing. Flaps, wings, landing gear contribute significantly to the total sound emission. This paper aims to present a passive flow control (in the sense that there is no power input) to reduce the noise radiation induced by the flow over the cavity of the landing gear during take-off and landing.

The understanding of the noise source mechanism is normally caused by the unsteady interactions between the cavity surface and the turbulent flows as well as some studies that have shown tonal noise because of cavity resonances; this tonal noise is dependent on cavity geometry and incoming flow that lead us to use of a sinusoidal surface modification application upstream of a cavity as a passive acoustics control device in approach conditions.

It is demonstrated that the proposed surface waviness showed a potential reduction in cavity resonance and in the overall sound pressure level at the majority of the points investigated in the low Mach number. Furthermore, optimum sinusoidal amplitude and frequency were determined by the means of a two-dimensional computational fluid dynamics analysis for a cavity with a length to depth ratio of four.

The noise control by surface waviness has not implemented in real flight test yet, as all the tests are conducted in the credible numerical simulation.

The application of passive control method on the cavity requires a global aerodynamic study of the air frame is a matter of ongoing debate between aerodynamicists and acousticians. The latter is aimed at the reduction of the noise, whereas the former fears a corruption of flow conditions. To balance aerodynamic performance and acoustics, the use of the surface waviness in cavity leading edge is the most optimal solution.

The proposed leading-edge modification it has important theoretical basis and reference value for engineering application it can meet the demands of engineering practice. Particularly, to contribute to the reduce the aircraft noise adopted by the “European Visions 2020”.

The investigate cavity noise with and without surface waviness generation and propagation by using a hybrid approach, the computation of flow based on the large-eddy simulation method, is decoupled from the computation of sound, which can be performed during a post-processing based on Curle’s acoustic analogy as implemented in OpenFOAM.

The purpose of this paper is to present the results of mixing promotion and screech frequency of controlled elliptical supersonic jet.

Flow field characteristics of low-aspect-ratio elliptical jets are examined at over-expanded, under-expanded and correctly expanded conditions. The tabs are placed at elliptical jet exit along the major and minor axes.

The results show that the mixing done by the minor axis is superior to the tabs along major axis. At all pressure ratios, the content of jet noise and the frequency are high for the tabs along the major axis because of increase in the amplitude of screech frequency. Further the tabs along minor axis show a dominance of large-scale vertical structures. In under-expanded conditions, the shock cell shows the rapid change because of the presence of tabs. The tabs along minor axis are making the shock weaker, hence no evidence of axis switching.

To achieve the greater performance of jet, the authors need to reduce the potential core length of the issuing jet. This can be achieved by implementing different types of tabs at the exit of the nozzle.

The present paper represents the flow of controlled jet using inverted triangular tabs. By achieving the controlled jet flow, the performance of propulsion systems can be improved. This can be used in systems such as combustion chamber, missile’s noise reduction and thrust vector control.

Compiled by K.G.B. Bakewell covering the following journals published by MCB University Press: Facilities Volumes 8‐18; Journal of Property Investment & Finance Volumes 8‐18; Property Management Volumes 8‐18; Structural Survey Volumes 8‐18.

Index by subjects, compiled by K.G.B. Bakewell covering the following journals: Facilities Volumes 8‐18; Journal of Property Investment & Finance Volumes 8‐18; Property Management Volumes 8‐18; Structural Survey Volumes 8‐18.

Compiled by K.G.B. Bakewell covering the following journals published by MCB University Press: Facilities Volumes 8‐18; Journal of Property Investment & Finance Volumes 8‐18; Property Management Volumes 8‐18; Structural Survey Volumes 8‐18.

Compiled by K.G.B. Bakewell covering the following journals published by MCB University Press: Facilities Volumes 8‐18; Journal of Property Investment & Finance Volumes 8‐18; Property Management Volumes 8‐18; Structural Survey Volumes 8‐18.

This paper aims to investigate the aerodynamic sound generated from flow over bluff bodies at a high Reynolds number. By taking circular and square cylinders as two representative geometries for the cross-section of bluff bodies, this study aims to clarify the difference in flow formation and sound generation between the two types of bluff bodies. Furthermore, the possibility for a downstream flat plate to be used as sound cancellation passive mechanism is also discussed in this study.

Sound source from the near field is numerically solved by using the Unsteady Reynolds-Averaged Navier Stokes equations. While for the sound at far-field, the compact sound theory of Curle’s analogy is used.

Magnitude of the generated sound is dominant by the aerodynamic forcer fluctuations, i.e. lift and drag, where the lift fluctuation gives the strongest influence on the sound generation. The square cylinder emits 4.7 dB higher than the sound emitted from flow over the circular cylinder. This relates to the longer vortex formation length for the case of square cylinder that provides space for more vortex to dissipate. It is suggested that downstream flat plate is possible to be applied for a sound cancellation mechanism for the case of circular cylinder, but it would be more challenging for the case of square cylinder.

This study include implications for the development of noise reduction study especially in high-speed vehicles such as the aircrafts and high-speed trains.

This study identified that there is possible method for sound cancellation in flow over bluff body cases by using passive control method, even in flow at high Reynolds number.

The purpose of this research is to study and investigate the flow control of 0.8 Mach jet using three tab configurations. The tabs with the slots will eventually lead to generation of vortices and thus enhances the mixing characteristics.

The jet flow control is achieved by the usage of three tabs, namely, Tab A, Tab B and Tab C that are placed at the exit plane of the convergent nozzle at 180 degrees apart. Three tabs with different slot profile are designed with the same constant blockage ratio of 7.3%. The tabs produce vortices of varying sizes that directly influence and modify the jet structure, thereby enhancing the efficiency in mass entrainment and mixing. The tabs are studied numerically first and then are compared with the results of the experiments.

The results are compared with that of the results of the uncontrolled jet. For Mach 0.8 jet, Tab C is found to reduce the core length and gives reduction of 90.23%, in comparison to Tab A and Tab B, which provides 84.1% and 87.79%, respectively. The results of numerical are then compared with the centerline results obtained via experiments. With the engagement of Tabs A, B and C, the jet structure is seen to have been modified at Mach 0.8 with Tab C performing better.

The tabs are a passive control device that can be practically enabled in the aircraft nozzles to control the flow and even suppress the noise emanated by the jet. Tabs can be effectively used for better thrust vector control and assist in jet noise suppression. Thus, this study on tabs and its uses are important and essential in aerospace technology.

This particular study on mechanical slotted tabs is innovatively carried out by designing the tabs in such a way that one such has not been designed before. The slots run through the adjacent sides of the tabs which is a novelty in itself, whereas perforations made only through the opposite sides of the tabs are studied by various researchers till now. The slots in the adjacent faces modify the flow physics in such a way that it enhances mixing by the creation of turbulence because of the interaction between the main stream and the secondary jet exactly at the core. So far, such slots and profiles are not investigated. By the usage of such tabs, the flow to mix faster is much closer to the core of the jet by creating mixed size vortices and thus has higher efficiency.

The purpose of this paper is to describe a programme of research into an innovative approach to whole‐house ventilation with heat reclaim. In order to save energy, houses are now required to be constructed to a high level of air tightness. This poses potential problems of indoor air quality, condensation and mould growth, with implications for human health. Adequate and controlled ventilation is a necessity, and in Europe the adoption of mechanical systems incorporating heat reclaim has become the preferred technology. The relatively mild climate of the UK undermines the efficiency of these fan‐driven solutions. The programme of research has been to test the viability of an engineered system of natural ventilation for use in temperate regions.

The system works by the combination of “supply air” windows and passive stacks. The windows have an air path for incoming ventilation that passes between panes of glass, the pressure drop across the windows to induce the air flow through them is provided by the passive stacks in kitchens and bathrooms. Passive stacks are an alternative to the use of extract fans; they have been included in the building regulations since their efficacy was proven by research carried out at the Building Research Establishment in the 1980s. “Supply air” windows are manufactured in Finland, and have also been researched in Canada. The research described in this paper is the first to combine “supply air” windows and passive stacks to form a system that is completely natural and operates without the use of electricity. It has been carried out over the course of a number of projects. Beginning with laboratory studies that established the design dimensions for the windows, followed by test cell measurements, and then installation in real buildings monitored, both empty and occupied. Each stage was validated in relation to simulation models.

It was demonstrated that window U‐values of down to 0.6 W/m²/°C can be achieved. It has been demonstrated in real building applications that a reduction in overall household heating consumption of 20 per cent is attained in dwellings where the system has been installed. User approval, which was the focus of the later projects carried out in Norwich, has also been high.

The windows have no special installation requirements and passive stacks are a catalogue component. The windows are designed as two separate sashes that are locked together by catches that can be undone to clean the space between the panes. The system is an alternative to mechanical ventilation heat reclaim systems, it is a simple low maintenance, low‐cost method that offers good indoor air quality as well as energy advantages, which has been shown to be particularly suited to the typical winter climate conditions in the UK.

Stress damages us and our performance. It is a real part of most manager's experience and can be said to occur when significant demands exceed perceived management responsibilities and routines. Stress can be the essence of working life, and certainly need not always be damaging to us. But when it becomes excessive, it is something unwanted.