The behaviour of two one-way type suspension roof models in a smooth flow was investigated. One model had bracing cables and the other did not. Mean values, rms values and spectral density functions of vertical displacements of the models were measured.Natural frequencies, especially that of the symmetric first mode, of the model which did not have bracing cables decreased as flow velocity increased.Oscillation consisted mainly of the oscillations in the symmetric first mode and in the anti-symmetric first mode.Mean and rms values of the displacements were calculated from characteristics of pressure fields on rigid roof models on the assumption that movement of roofs had no effect on the pressure field. The measured and calculated results were compared and effects of roof movement were discussed.It appeared that roof movement had no significant effect on the mean pressure field. However, it had a significant effect on the fluctuating pressure field at a flow velocity range. An oscillation in the anti-symmetric first mode, which appeared to be a self-excited oscillation, occurred to both models in the flow velocity range.
There are any methods of producing a shear flow in wind tunnel.However, most of them accompany relatively high turbulence level of about 5 %.Herein, a method to produce low turbulence uniform shear flow is introduced, which was riginally developed by Davies (1957) and Elder (1959) and was later modified by Moult (1969).The method uses a curved gauze to produce a linear velocity profile.The authors further modified the gauze method, and produced uniform shear flows with large velocity gradient.The flows were found to have the turbulence level of about 0.6% in a moderately well designed wind tunnel.
Large-scale structures sometimes cause a considerable temperature drop around it in winter nights, which often results in a serious damage to crops.This micrometeorological problem is very serious in some regions;it is an important item of environmental assessment. Stagnation of chilled night air is the essence of the problem.Analysis of this problem requires the study of the natural convective flow which is generated by the radiative cooling of the ground surface.Numerical method is profitably applicable to this problem.In this paper the fundamental process is described and the governing equations are presented;massconservation transport of momentum, diffusion of energy and heat balance. Once the flow field is determined, conventional meteorological procedures enable the environmental assessment.Numerical examples are also presented.
Various methods for wind field computation from sparse observed wind data are summarized. The procedure for the computation of wind field based on these methods is as follows. (1).Computation of grid-point values of wind components by interpolating and extrapolating observed wind data. (2).Adjustment for the wind vectors obtained in procedure (1) to make them non-divergent An objective analysis procedure is employed to adjust the wind vectors at each grid point. The methods summarized in this report are therefore called an objective analysis technique.
The world energy problem has stimdlated interest in the application of wind power. The attempts have been made to develop wind power systems as auxiliary supplies for local energy. The main motivation for this study is to clarify the performance of a wind power system. In this paper, the performance has been analyzed by means of analog simulation.From the results of the simulation, it is seen that the characteristics are affected considerably nature of wind and each parameter of a wind power system.