Closure to “Discussion on ‘Damping and Inertia Coefficients for Two End Sealed Squeeze Film Dampers With a Central Groove: Measurements and Predictions,’” (2013, ASME Paper No. GT2013-94273).

Abstract

The authors thank Professor Mihai Arghir for having performed the computational fluid dynamics (CFD) simulations of the flow fields for the two test damper configurations. The predictions demonstrate, as expected, the flow field in the deep feed groove and lubricated through feed holes to be extremely complicated. The brief discussion on the evolution of the flow patterns (vortices) along the various planes of observation is most enlightening.As per the question, “how can the magnitude of the groove effective depth be objectively selected knowing that the flow field is so complex?” the authors concur with Dr. Arghir's judgment, that is, one cannot ascertain the effective groove depth from simple knowledge of fluid mechanics. The effective depth depends not only on the geometry of the groove and adjacent film land but also on the lubricant properties and the operating conditions. That is, as stated in the original development analyses of Refs. [19,20] from the discussion, the effective groove depth is an empirical parameter to be determined from matching experimental results to predictions or extracted from a careful assessment of numerical predictions obtained from complete CFD simulations.An example of the first instance is offered by the current paper where the effective depth is obtained from correlating (only) one experimental parameter, namely a force coefficient, to predictions obtained by continuously varying the groove depth when solving the extended Reynolds equation for a centered journal condition. References [26,27] from the discussion and Ref. [1] offer full details on the matching procedure and note the good agreement of predictions to the experimental results for most off-centered or eccentric journal conditions, small to large orbit radii, and multiple frequencies.Recent CFD research [2,3] demonstrates, as Professor Arghir has done, the complexity of the flow field in even simple squeeze film dampers. Most importantly; however, is for the damper practitioner to realize that classical lubrication theory, which regards a feed groove as a region of stagnant fluid and impervious to the kinematics of journal motion, is plain wrong.The authors express their sincere gratitude to Dr. Arghir. In this time and age where everyone is so busy, having taken the time to understand and to enlighten the work of others is a rarity—a demonstration that someone cares. Discussions to published papers are nowadays an unfortunate anachronism.