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The objective of this paper is to report the effects of Reynolds number and hub-to-tip ratio on the performance of the impulse turbine for wave energy conversion. The turbine was investigated experimentally under steady and sinusoidally oscillating flow conditions by model testing. As a result, it was found that the critical value of Reynolds number and the optimum hub-to-tip ratio am approximately 4.0 X [10.sup.4] and O. 7, respectively: Furthermore, their effect on starting characteristics have been clarified.

A Wells turbine for wave power conversion has hysteretic characteristics in a reciprocating flow. The counterclockwise hysteretic loop of the Wells turbine is opposite to the clockwise one of the well-known dynamic stall of an airfoil. In this paper, the mechanism of the hysteretic behavior was elucidated by an unsteady three-dimensional Navier-Stokes numerical simulation. It was found that the hysteretic behavior was associated with a streamwise vortical flow appearing near the blade suction surface. In the accelerating process of axial flow velocity, the vortex is intensified to enlarge the flow separation area on the blade suction surface. In the decelerating flow process, the flow separation area is reduced because of the weakened vortex. Therefore, the aerodynamic performance in the accelerating flow process is lower than in the decelerating flow process, unlike the dynamic stall. Based on the vortex theorem, the mechanism to vary the intensity of the vortex can be explained by the trailing vortices associated with the change in the blade circulation.

Railway train aerodynamic problems are closely associated with the flows occurring around train. Much effort to speed up the train system has to date been paid on the improvement of electric motor power rather than understanding the flow around the train. This has led to larger energy losses and performance deterioration of the train system, since the flows around train are more disturbed due to turbulence of the increased speed of the train, and consequently the flow energies are converted to aerodynamic drag, noise and vibrations. With the speed-up of train, many engineering problems which have been neglected at low train speeds, are being raised with regard to aerodynamic noise and vibrations, impulse forces occurring as two trains intersect each other, impulse wave at the exit of tunnel, ear discomfort of passengers inside train, etc. These are of major limitation factors to the speed-up of train system. The present review addresses the state of the art on the aerodynamic and aeroacoustic problems of high-speed railway train and highlights proper control strategies to alleviate undesirable aerodynamic problems of high-speed railway train system. Keywords: Train aerodynamics; Impulse noise; Train tunnel; Compressible flow; Unsteady flow; Aerodynamic drag

This work investigated an air turbine with self-pitch-controlled blades operating in the airflow generated by an oscillating water column (OWC) under irregular wave conditions to determine turbine performance and identify the optimum blade pitch angle setting. Rotor models with fixed blades were tested under steady flow conditions. The running and starting characteristics of the turbine under irregular wave conditions were determined from a computer simulation that modeled both the turbine and the air chamber The performance of the air turbine was evaluated and the optimum rotor blade limit was found to be about 10 [degrees] . [DOI: 10.1115/1.1408306] Keywords: Fluid Machinery, Wave Power Conversion, Air Turbine, Self-Pitch-Controlled Blade, Ocean Wave

The current understanding of the mechanism of origin and propagation of impulse noise from sources such as blasting, high speed train in a tunnel, sonic boom, muzzle blast and engine exhaust is reviewed. The state of the art on prediction methods and control techniques available are described. The need to develop a further understanding of the impulse noise is stressed.