Experimental Observation of Squeeze Film Damper Executing Offset Circular Whirl

State-of-the-art knowledge about the squeeze film damper (SFD) has been pithily commented in a recent paper [1] putting in evidence the limits that still affect the application to practical cases, despite a sensible quantity of theoretical and experimental work that has been carried out in a long-lasting activity of research in the field [3, 4]. In particular, the heavy influence of film cavitation on SFD performances, with its very likely to set in character that affects most of the common operative conditions, still represents a strong motive for investigation. Many researchers have significantly contributed to clarify, among other aspects, the characteristics of film rupture within SFD (for instance [5, 6]). Recent work [7, 8] has stressed the importance of a common mechanism of cavitation that manifests with air ingestion in the film and consequent formation of bubbly-mixtures. In these conditions, the decaying damping forces can lower till to 15 percent of those pertaining to normal conditions in the absence of cavitation. Under these premises, an experimental work has been carried out about a damper executing offset circular whirl, in line with a previous investigation [2], focusing attention on waveform of pressure signals. Film rupture with vapor cavitation or gaseous cavitation, due to air suction, was observed. The former type was prevailing and frequently accompanied by a region with tensile stresses. Operating conditions with co-presence of both mechanisms of film rupture were also detected.