It is proposed in this work that the transition to slug flow occurs due to Kelvin-Helmholtz instability, which, in this case, is enhanced by the proximity of the upper wall and becomes wave-amplitude dependent. Since the surface waves possess a limiting amplitude, the transition can be predicted by examining whether the highest possible waves are unstable. The theoretical prediction is in good agreement with the authors’ experimental results. It also agrees reasonably well with Baker’s and Schicht’s flow pattern charts for strictly horizontal channels, but it exhibits large differences when the channels deviate somewhat from the horizontal.
The investigation deals with the “spin-up” of the liquid partially filling a right circular cylinder which is impulsively accelerated from rest to a constant angular velocity. By application of certain simplifying assumptions, a simplification of the Navier-Stokes equations is obtained and numerically solved, obtaining the unsteady angular velocity distribution of the liquid and the configuration of the liquid’s free surface, as it approaches, asymptotically with time, a paraboloid. The simplifying assumptions are qualitatively verified by experiment. Measurement of the theoretically predicted free-surface configuration is obtained by an electrohydraulic servosystem designed and developed for the problem. Good agreement between experiment and theory is obtained.
Statements in the literature appear to imply that the numerical value of the circumferential stress in thick-walled cylinders is always a maximum at the inner radius. While this is certainly correct in the case of zero external pressure, the presence of both external and internal pressures creates the possibility of a numerically larger tangential stress occurring at the outer radius. This paper investigates this possibility and establishes a criterion for a check on the location of the numerical tangential stress maximum. A chart is presented for its convenient application.
An experimental self-starting hydrodynamic gas bearing was designed, built, and tested. This bearing operates on the principle that the bearing is started and stopped hydrostatically by means of an air supply which is generated by the bearing itself. For this purpose, a portion of the self-starting bearing is executed as a herringbone grooved bearing, which performs as a pump, charging a reservoir during hydrodynamic operation of the bearing. The reservoir air supply generated by the herringbone bearing is used for hydrostatic operation of the bearing during starts and stops. Starting and stopping of the experimental bearing was demonstrated using the air supply generated by the herringbone bearing. An equation was derived for the mass flow rate of the herringbone bearing pump.
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