An analysis, based on the narrow groove theory, is presented for the closed, spiral-grooved spool bearing. Designs optimized for static stiffness are obtained for range of values of the groove extent parameter Y, and the characteristics of these designs under oscillatory motion are investigated over a wide frequency spectrum. It is shown that the geometry of the boundaries common to thrust and journal sections has an appreciable effect on the dynamic compliance of the bearing, and that a relief volume between the bearing sections can give rise to a gas film resonance, at which the compliance is strongly dependent on the dimensions of this volume. The beneficial effect of a thrust-bearing seal region with respect to this type of resonance is demonstrated, and it is shown that a design for optimum static stiffness differs considerably from one for optimum dynamic stiffness. It is the prediction of this analysis that a small sacrifice in static performance can lead to considerable gains in the performance under dynamic conditions.

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