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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.

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Council, Reports and Technical Memoranda of the United States National Advisory Committee for Aeronautics and publications of other similar Research Bodies as issued.

The prediction of critical velocity at instability threshold for shell and tube heat exchangers is important to avoid failure of tubes as a result of flow-induced vibrations due to water cross flow. The flow-induced vibration in finned tube heat exchangers is affected by various parameters such as fin height, fin pitch, fin material, tube array, pitch ratio, fin type, fluid velocity etc. In this paper, an experimental investigation of fluid elastic instability in shell and tube heat exchangers is carried out by subjecting normal square finned tube arrays of pitch ratio 1.79 to water cross flow.

The five tube arrays, namely plain array, two finned tube arrays with 3 fpi and 9 fpi fin density, and two finned tube arrays with 3 mm and 6 mm fin height are tested in the experimental test setup with water flow loop and vibration measurement system. The research objective is to evaluate the effect of fin density and fin height on the instability threshold. The critical velocity at instability threshold is determined to characterize the fluid elastic instability behavior of different tube arrays. The vortex shedding behavior of the tube arrays is also studied by determining Strouhal number corresponding to the small peaks before fluid elastic instability.

The fluid elastic instability behavior of the tube arrays was found to be the function of fin tube parameters. The experimental results indicate that an increase in fin density and fin height results in delaying the instability threshold for finned tube arrays. It is also observed that critical velocity at instability is increased for finned tube arrays compared to plain tube arrays of the same pitch ratio. The design modifications in the outer box have resulted in further reduction in the natural frequency. This enabled to reach clear instability for all the five-tube arrays.

The research data add the value to the present body of knowledge by knowing the effect of fin height and fin density on the fluid elastic instability threshold of normal square finned tube arrays subjected to water cross flow.

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Council, Technical Reports and Translations of the United States National Aeronautics and Space Administration and publications of other similar Research Bodies as issued.

Under this heading published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Council, Reports and Technical Memoranda of the United States National Advisory Committee for Aeronautics and publications of other similar Research Bodies as issued.

I'VE said it before, and I'll say it again: Eastbourne is an excellent place for a conference, and I set out for it after five years' absence with the hope that its handsome and genial presence would produce something better than the mixture of ordinary, obvious and sometimes inaudible papers that have been a constituent of more than one intervening conference. That towns can affect such occasions is no doubt a farfetched conceit, but they certainly affect me; as soon as I arrived the environmental magic worked, and old friends and new faces were seen in the golden light of perfect autumn weather.

The study of markets encompasses a number of disciplines – including anthropology, economics, history, and sociology – and a larger number of theoretical frameworks (see Plattner, 1989; Reddy, 1984; Smelser & Swedberg, 1994). Despite this disciplinary and theoretical diversity, scholarship on markets tends toward either realist or constructionist accounts (Dobbin, 1994; Dowd & Dobbin, forthcoming).¹ Realist accounts treat markets as extant arenas that mostly (or should) conform to a singular ideal-type. Realists thus take the existence of markets as given and examine factors that supposedly shape all markets in a similar fashion. When explaining market outcomes, they tout such factors as competition, demand, and technology; moreover, they can treat the impact of these factors as little influenced by context. Constructionist accounts treat markets as emergent arenas that result in a remarkable variety of types. They problematize the existence of markets and examine how contextual factors contribute to this variety. When explaining market outcomes, some show that social relations and/or cultural assumptions found in a particular setting can qualify the impact of competition (Uzzi, 1997), demand (Peiss, 1998), and technology (Fischer, 1992). Constructionists thus stress the contingent, rather than universal, processes that shape markets.