Water leak diagnosis of tiled roofs under vibration and scattering by wind tunnel experiment
This paper describes a water leak test of roof tiles. The 100 roof tiles were set up on 10 lines and 10 rows on the pitched roof in the downstream of the flow from the wind tunnel. The flow velocity was increased gradually from the low velocity to the high velocity, and the effects of the wind on the roof tiles were investigated by the water leak test. The situation of the water leak test was filmed by video camera. Two accelerometers were simultaneously used. The roof tiles which showed significant vibration at any velocity were found in a series of experiments and the accelerometers were attached to the two neighboring roof tiles on the model roof. The water leak phenomena in the experiment by using the artificial rainfall apparatus are discussed in this paper. Some mechanisms with relatively large amplitudes at low-frequency vibrations, which caused water leak phenomena were made clear.
Researches on Vibration and Scattering of Roof Tiles by Wind Tunnel Test (2nd Report, Effect of Vibration on Scattering of Roof Tiles)
風洞実験によるかわらの振動と飛散現象の研究* (第2報,か わ らの飛散に及ぼす振動の影響) 難 波 礼 治*1, 岡 本 覚*2 奥 田 昭 博*1, 芝 尾 宜 秀*3 Researches on Vibration and Scattering of Roof Tiles by Wind Tunnel Test (2nd Report, Effect of Vibration on Scattering of Roof Tiles) Reiji NANBA, Satoru OKAMOTO *4, Akihiro OKUDA and Yoshihide SHIBAO *4 Interdisciplinary F culty of Science andEngineering , Shimane University, 1060 Nishikawatsu-machi, Matsue-shi, Shimane, 690-8504 Japan This study has investigated the nature and source of the vibrating and scattering behavior of roof tiles with the aim of providing a better insight to the mechanism. The 100 roof tiles were set up on 10 lines and 10 lows on the pitched roof in the downstream of the flow from the wind tunnel. These experiments were followed by series of tests where the slope angle of the roof tiles was changed. The vibrations of the roof tiles were simultaneously measured by the two accelerometers, and the motions of the vibration and scattering were observed by the high-speed video camera. The frequency response function and coherence function of roof tile were measured by impact hammer test under no flow condition. Just before scattering of the roof tiles, both vibrations of higher frequency mode and vibrations of lower frequency mode appeared simultaneously in roof tiles. The values of the higher frequencies were corresponding to the values of resonant frequencies of the roof tiles. It was thought that the scattering of roof tiles was influenced by the vibration of the lower frequency mode. The frequencies of the vibration were measured by the high-speed video camera system. The values of the lower frequencies were 10 Hz-20 Hz. The mechanism of scattering of roof tiles could be understood by means of the information from the accelerations and the images of roof tiles.
Thermally Induced Dynamics of Satellite Solar Panels
Thermally induced structural motions are known to affect the attitude dynamics of low Earth orbiting satellites during eclipse transitions. Motions of e exible appendages such as solar panels lead to rigid body rotations of the entire satellite because the total angular momentum of the system is conserved. These potentially large attitude disturbances may violate pointing accuracy and jitter requirements. One type of thermally induced dynamics exhibited by solar panels is thermal snap. The Upper Atmosphere Research Satellite is a prominent example of a satellite that experiences thermal snap disturbances during eclipse transitions. This paper describes recent studies of thermally induced dynamicsof solarpanels, including an analysisofsatelliteattitudedynamics resulting from thermally induced structural motions and a laboratory investigation of the thermal-structural performance of a satellite solar panel. Analytical and experimental results demonstrate thermal bending deformations with acceleration transients that have characteristic thermal snap disturbance histories in response to rapid changes in heating. The studies show that solar panel thermal snap disturbances are caused by through-the-thickness temperature differences that vary at a nonconstant rate. Finite element analysis correctly predicts the thermal snap phenomenon observed in the solar panel experiments.