Influence of a Reynolds number on flow and aerodynamic and aeroelastic characteristics of bluff bodies with a cross section with cut corners, such as a cross- section of a tower of a suspension bridge has been studied using a wind tunnel. Pressure distribution on bodies and Strouhal frequencies have been measured, and a series of free oscillation tests for models with different cut corner and supported with different coil-springs have been carried out in a relatively wide range of Reynolds number based on a resonance velocity, in order to clarify effects of the height of cut corners and influence of Reynolds number on an oscillatory behaviour of bodies. Measured results proves the existence of the critical Reynolds number accompanied with the drastic change of a flow pattern, which is confirmed by the flow visualization technique. The values of the critical Reynolds numbers strongly depend upon a height of cut corners of a model.
A series of wind tunnel tests were performed to investigate the variation of the surface drag caused by different array patterns of roughness elements. The drag on the rough surface using cubic blocks was directly measured by a float built in the floor of the wind tunnel. The direct measurement by the float was comparablly reliable when compared with other three different ways of drag measurement. The variation of the surface drag coefficient Cr caused by array patterns has been examined. The relationship between Cr and the 'roughness concentration' ratio λ element frontal area/surface area per element, showed that the randomarrayed distribution was equivalent to the staggered arrayed pattern with the elements facing to the wind at an angle of 45°
This paper describes studies on wind-duration of strong wind, which is one of the factor for analysing fatigue damage of structures sujected to repeated wind load. In this paper, observed wind data, which is record with duration 72 hours at the center of which annual maximum wind speeds occurs, were used to estimate duration and probability of wind velocity. Generalized probability distribution function of wind velocity were proposed. Duration of strong winds presented as a function of its maximum wind velocity. From these results, multipling generalized probability distribution function by generalized number of (wind velocity) samples, approximate equation of wind-duration was derived. Approximate equation of wind-duration proposed in this Papers useful for analysing fatigue damage of structures under strong wind in Japan.
An Effel-type boundary layer wind tunnel has been installed at Dept. of Arch., University of Tokyo to examine flows in the wind tunnel and also to propose basic specifications of wind tunnels for both environmental and structural engineering purposes. The working section of the wind tunnel is 0.7m in height, 1.0m in width, and 4.2m in length. The range of wind speed is from 0.5 to 15.0m/s and the uniformity of mean wind speed and the intensity of turbulence are within ± 1.8%, 1.5%, respectively. Characteristics of the boundary layer flow made by spires and roughness blocks in the wind tunnel are also presented in this paper.