A review of the various optical methods to detect ultrasound (bulk and surface waves) at the surface of opaque solids is presented. The most useful techniques are thoroughly analyzed. Their performance when nonideal conditions are encountered, such as vibrations, air turbulence, and rough light scattering surfaces is evaluated. This review includes a description of knife-edge techniques, optical heterodyning, differential interferometry, and velocity (time-delay) interferometry methods, plus a mention of various less-important tech-

Optical Detection of Ultrasound

The flow behavior in the riser of a circulating fluidized-bed reactor was studied experimentally and computationally. Laser Doppler anemometry was applied to measure the flow behavior of FCC catalysts. Particle diameter and mean and fluctuating velocity for different particle sizes were measured at different flow conditions. A typical core-annulus flow with a relative velocity between particles of different sizes was obtained. A significant radial segregation of the mean diameter was measured in the riser. A multi-fluid computational fluid dynamics model was developed and verified against the experimental results. The flow model is based on a Eulerian description of the phases where the kinetic theory for granular flow forms the basis for the turbulence modeling in the solid phases. The model is generalized for one gas phase and N number of solids phases to enable a realistic description of the particle-size distribution in gas/solid flow systems. Each solid phase is characterized by a diameter, form factor, density, and restitution coefficient. Simulations with one gas and two solid phases were conducted, and the computational results agreed generally well with the measurements.

Experimental and computational study of multiphase gas/particle flow in a CFB riser

Velocity measurements in a two-phase turbulent jet

The concept, design, and construction of a directionally sensitive laser velocimeter for unsteady flow measurements are presented. Oscillatory flow measurements are compared with theoretical predictions.

Oscillatory Flow Measurements with a Directionally Sensitive Laser Velocimeter

The application of laser anemometry to the study of turbulent supersonic flow is discussed. An analysis is presented showing that the direct frequency method of measurement of the Doppler shift in frequency undergone by light scattered from flow borne particles using a single frequency laser and a Fabry-Perot interferometer has significant advantages over optical heterodyning. It is shown that a confocal rather than a plane Fabry-Perot used in conjunction with an argon laser is the most suitable instrumentation for this application. Preliminary results are presented of measurements made on a supersonic wind tunnel and a free jet.

https://iopscience.iop.org/article/10.1088/0022-3735/4/3/006/pdf

W. R. Babcock

Papers

A laser-Doppler technique for the measurement of particle velocity.