摘要
The aerodynamic, or more generally fluid-dynamic, instability of the downstream circular cylinder in the wake of a similar cylinder in subcritical flow is the focal point of this paper. These phenomena are known to cause fatigue problems and impair the serviceability and safety of structures in various engineering fields. The aim of this study is to clarify the mechanism of this phenomena, as well as to find the conditions under which vibrations occur. A series of wind tunnel experiments and corresponding flow visualization in a water flume were conducted to permit discussion of the unsteady pressure properties, the aerodynamic unsteady force characteristics including its nonlinearity, and their relationship to the flow patterns. The sudden decrease in pressure on the inward surface of the downstream cylinder when it approaches the upstream one, appears to play an important role in the vibration. Furthermore, an analogy between the unsteady aerodynamic force properties of the downstream cylinder and those of an isolated bluff body which undergoes both torsional and coupled flutter is postulated. © 1990.