Study on fluid-elastic vibration of tube bundle

Many fluid equipments using circular tube bundles have been employed in various plants, but recently, the vibration troubles of circular tube bundles become remarkable, accompanying the increase of flow rate. Such vibration of circular tube bundles induced by fluid is hydrodynamic elastic vibration, but it has not necessarily been explained sufficiently. It was found that the fluid force working on a row of columns was considerably different from quasistatic fluid force. The same problem seems to exist also in many rows of columns, therefore the unsteady fluid force working on many rows of columns was measured, and the hydrodynamic elastic vibration induced by it was studied. The vibration phenomenon was modeled, assuming that the motion of five columns affects fluid force. The equation of motion of columns is derived. According to the measurement, the fluid force in many rows of columns seemed to increase as compared with that in case of one row. The test to determine the critical velocity for vibration generation was carried out, and the critical velocity was calculated, using the unsteady fluid force. These results are reported. The assumed vibration model was almost appropriate. (Kako, I.)