Fluttering Behavior of a Flexible Thin Sheet in High Speed Air Flow

点击翻译按钮获取中文摘要

Process of moving and/or handling in air at high speed a very thin and flexible sheet of such as paper, plastic film, cloth, thin metal plate, etc. are utilized in many fields of industry. Accelerating such processes tends to cause fluttering of the sheet, thus having adverse effects on the product quality and the production efficiency. The phenomena are considered to be of aeroelastic instability (flutter) induced by the interference of the sheet elastic behavior and the aerodynamic excitation. This investigation aimed to establish a method for prediction and elucidation of the phenomena on both theoretical and experimental bases.Tests were conducted on sheets of papers with the leading edge fixed and the trailing edge freely blown in a small wind tunnel ; experimental data on flutter speeds, frequencies, and modes, etc. were collected for a wide variety of the sheet conditions. The experimental flutter limits were found to form a clear boundary in terms of relative stiffness (stiffness/dynamic pressure) vs.mass ratio, and the vibrational characteristics were summarized in terms of reduced frequency vs.mass ratio..At the same time, a prediction method of the flutter condition was developed utilizing a distributed vortex method for the fluid dynamics and an elastic beam theory for the sheet dynamics on the assumption of small perturbation. Results predicted by the method gave good agreement with the above experimental data and explained well the characteristics of the phenomena observed.It is also necessary to know about the effects of external disturbances tending easily to affect very thin sheets. This investigation includes experimentally obtained informations on such concerns.Thus the investigation, both experimental and theoretical, succeeded in forming a basis and providing a useful means for evaluating and tackling the practical situations.