Showing papers in "Journal of Basic Engineering in 1965"

Use of hydrogen bubbles for quantitative determination of time dependent velocity fields in low speed water flows

Abstract: : Improved flow visualization methods based on the hydorogen bubble technique are described. Use of 'combinedstreak markers' allows quantitative measurement of the instantaneous velocity field in a plane as a function of time in low speed water flows. Adaptation to a great variety of situations using different probe techniques is possible. Disturbance to the flow is very small. Adequate accuracy is obtainable. The method offers the advantage of simultaneous visual images of the flow structure and quantitative measurement of velocity over a finite region. It also allows some types of measurements not previously possible. Limitations of the method include its restriction to low speed water flows and the observation of fluctuations only at low frequencies. Practical difficulties occur due to probe frangibility and problems of uniform bubble production. Part I describes the underlying concepts, summarizes the history of the method and describes operating experience to date at Educational Services, Incorporated and Stanford University. Part II is a detailed analysis of the uncertainties in velocity measurements using combined-time-streak markers formed by hydrogen bubbles. (Author)

Characteristics of Herringbone-Grooved, Gas-Lubricated Journal Bearings

Abstract: : A differential equation is obtained for the smoothed overall pressure distribution around a herringbone-grooved, gas-lubricated, journal bearing operating with a variable film thickness. The equation is based on the limiting case of an idealized bearing for which the number of grooves approaches an infinite number. A numerical solution to the differential equation is obtained valid for small eccentricities. This solution includes the case where the journal is undergoing steady circular whirl. In addition to the usual plain bearing parameters L/D and lambda, the behavior of a grooved bearing also depends on four additional parameters: The groove angle beta, the relative groove width alpha, the relative groove depth H sub o, and a compressibility number, lambda sub s, which is based on the relative speeds of the grooved and smooth members of the bearing. Results are presented showing bearing radial force and attitude angle as functions of beta, alpha, H sub o, the compressibility number lambda, and also whirl speed ration. (Author)

The Static and Dynamic Characteristics of the Spiral-Grooved Thrust Bearing

Abstract: : A generalized analysis for spiral-grooved thrust bearings is presented. The effect of local radius is considered. For the same inside-tooutside radius ratio, the inflow design is shown to be superior in the load capacity. The analysis also treats a relative, transverse, oscillatory motion of the bearing surfaces. Both the magnitude and phase angle (in the temporal sense) of the bearing reaction are dependent on the frequency of the motion. The results for the oscillating motion reveal the possibility of a self-excited, rotor-bearing instability. The criterion for determining the onset of this type of instability is given. (Author)

The Theory of the Infinitely Wide, Perfectly Flexible, Self-Acting Foil Bearing

Abstract: : The differential equations applicable to the film thickness beneath an infinitely wide, perfectly flexible self-acting tape are derived in the paper. Accurate numerical solutions are obtained for the film thickness in both the entrance and exit regions. These solutions have general applicability to situations where the entrance and exit regions are separated by a third region of uniform thickness. (Author)

Solution of the Stability Problem for 360 Deg Self-Acting, Gas-Lubricated Bearings

Abstract: Stability of self-acting gas lubricated journal bearings, using small perturbation and finite shaft orbit approaches

Cavitation Bubble Collapse in Viscous, Compressible Liquids—Numerical Analysis

Abstract: Numerical analysis of collapse of spherical bubble in compressible fluid, including surface tension, viscosity and adiabatic compression of gas within bubble

Surface Displacement of a Convective Elastic Half-Space Under an Arbitrarily Distributed Fast-Moving Heat Source

Abstract: : A solution of the normal displacement of the elastic half-space under an arbitrarily-distributed fast-moving heat source of constant velocity within the two-dimensional quasi-static, uncoupled thermoelasticity theory is presented. The surface of the half-space is allowed to dissipate heat by convection. Moreover, an example associated with the problem of elastohydrodynamics is given. (Author)

The Parameter Variation Problem in State Feedback Control Systems

Abstract: : The plant parameter variation problem in multivariable linear systems described by state vector equations is formulated using a new sensitivity measure. This formulation involves a direct comparison of open-loop and state feedback performance in the presence of parameter variations, and provides a basis for guaranteeing the superiority of the feedback design. Results are obtained for both continuous and discrete multiinput multi-output systems. Furthermore, it is shown for single-input multi-output plants that a low sensitivity design is also an optimal feedback control design with respect to a quadratic performance index. This provides a new interpretation of a similar result previously obtained by Kalman. (Author)