Masayuki Shimura

Wind-induced response of a large cantilevered roof

Abstract The subject of this study is to clarify aerodynamic properties of a large cantilevered roof. We conducted free vibration experiments in order to investigate effects of various parameters such as mass, pitch angle, and damping ratio to wind-induced vibration of the roof. In the experiments, we have found that the roof hardly vibrated at its natural frequency until a certain critical wind velocity, then a flutter-like vibration occurred and a sharp peak at frequency lower than the natural frequency appeared in a spectrum of the vibration. In the light of forced oscillation experiments, the frequency of the sharp peak was the natural frequency of the roof lowered by the positive aerodynamic stiffness. The lowered natural frequency synchronized with the frequency of the vortex shedding from the leading edge of the roof, which causes a negative damping effect of unsteady wind force.

A study on wind-induced vibration of super high rise building by multi-degree-of freedom model

Three types of multi-degree-of-freedom models of super high-rise buildings with side ratios of 11, 12 and 13 were made for boundary layer wind-tunnel tests. Each model was composed of six blocks to satisfy the similarity of the equivalent mass and stiffness of a 400 m high-rise building. Two methods were proposed to estimate the complex vibration mode from the measured data of columns strains. Both methods were based on the concept of the modal decomposition. The modal decomposition was carried out in space domain in the first method, and in frequency domain in the second method. Both methods worked well, but the second method is more feasible because it needs only one set of strain data at an arbitrary level. The vibrational behaviors of the three types of the models were examined by boundary layer wind-tunnel tests.

The Numerical Simulation of Snowdrift Around a Building

In this paper, we suggest a numerical simulation method of snowdrift. Two-dimensional numerical simulation method was first examined by comparison with the wind tunnel experiments. We found that the prediction method had the sufficient accuracy. Next, the simulation method was expanded to the three-dimensional simulation method. The simulation of snowdrift for the actual building was conducted to verify the applicability of the method. It became clear that the numerical simulation method was a useful tool to predict the snowdrift around the building.

Three Dimensional Numerical Flow Simulation Around Parallel Rectangular Cylinders

Abstract Noises of flow around parallel rectangular cylinders are likely to be caused by wind flow. According to the wind tunnel experiment, it is known that there are three kinds of special noises. Two kinds of noises occur when the wind comes from a perpendicular direction to the cylinders. These noises are caused by the vortex excited oscillation. Another noise occurs when the wind comes from an inclined direction to the cylinders. This noise is very high frequency, and its mechanism is not clear. Therefore in this study, the three dimensional numerical flow simulation is performed to clarify the high frequency noise of flow around parallel rectangular cylinders.