Messungen instationärer Drücke bei Queranströmung von Kreiszylindern unter Berücksichtigung fluidelastischer Effekte

摘要

Tubes of heat exchangers are excited to mechanical vibrations by unsteady flow forces. Up to now no information on the character of these forces and the interdependence between tube vibrations and the flow forces is known. An experimental device is described with which steady and unsteady forces acting on a tube and the mechanical response of the tube to these forces can be measured. The test tube and its neighbours were either fixed or free to vibrate. At first a single cylinder in cross-flow was investigated to prove the reliability of the test procedure. After that experiments with four in-line tube banks with transverse and longitudinal pitches ranging from 1.15 to 2.88 tube diameters were performed. The aerodynamic forces were calculated on line by means of an analogue computer. Simultaneously the mechanical response of the tubes was registered. The measurements show that four kinds of exciting mechanicms exist. Tube vibrations are caused either by vortices, buffeting, galloping of fluidelastic coupling. The tests were performed in an atmospherical wind tunnel in a range of Reynolds number 10$^{4}$ $le$ Re $le$ 10$^{5}$.