The Effects of an Annular Fluid on the Vibrations of a Long Rotor, Part 2—Test

Abstract

Analyses and tests were made to investigate the hydrodynamic mass and damping of a fluid in a thin annulus surrounding a rotor which is vibrating due to unbalance forces. The analysis is described in Part 1. This report describes the tests. Vibrational amplitudes were measured of a constant-speed rotor with various fluids and radius-to-clearance ratios. Axial flow was restricted by limited-leakage end seals. The fluid flow was considered to be either vortex or turbulent, based on the Taylor or Reynolds number. The presence of the fluid was found to lower the critical speed. This effect was ascribed to a hydrodynamic mass which was evaluated from the tests. Hydrodynamic masses were also determined for the rotor vibrating without rotation and were found to be in agreement with the results of Stokes [1]. All results were in reasonable agreement with the predictions of Part 1.