Index of content:
Volume 113, Issue 5, May 2003
- NONLINEAR ACOUSTICS 
113(2003); http://dx.doi.org/10.1121/1.1564022View Description Hide Description
Experiments on oscillating flow at the abrupt transition between a two-dimensional channel and essentially infinite space are presented. It is shown that phenomena associated with the transition are functions of three independent dimensionless parameters including the dimensionless radius rounding the edge of the end of the channel. The effect of each of these three parameters on the time-averaged pressure difference across the transition and the acoustic power dissipation is explored by holding two parameters fixed while varying the third. Evidence is presented that the losses due to oscillatory flow in this geometry are smaller than would be expected from commonly accepted values for steady flow in similar geometry.
Noncontacting lateral transportation using gas squeeze film generated by flexural traveling waves—Numerical analysis113(2003); http://dx.doi.org/10.1121/1.1564014View Description Hide Description
This paper presents the theory describing the dynamical behavior of a noncontacting lateral transportation of planer objects by means of a gas squeeze film created by traveling flexural waves of a driving surface. An oscillating motion in the normal direction between two surfaces can generate a gas film with an average pressure higher than the surrounding. This load-carrying phenomenon arises from the fact that a viscousflow cannot be instantaneously squeezed; therefore, fast vibrations give rise to a cushioning effect. Equilibrium is established through a balance between viscousflow forces and compressibility forces. When the oscillatory motion between two surfaces creates traveling waves, lateral viscous forces are generated in addition to the normal levitation forces. These forces are produced as a result of nonuniform pressure gradients in the lateral direction between the surfaces. The combination of normal and lateral forces could be used for transporting objects without any direct contact with the driving surface. The numerical algorithm in this work couples the squeeze film phenomenon, which is represented by means of finite difference equations, to model a variant of the Reynolds equation, together with the equations describing the dynamics of the floating object. Numerical simulations are presented and investigated to highlight noteworthy topics.