Three-dimensional measurements in gas flows

Abstract

This paper presents a series of experiments designed to extend the capability of laser diagnostic techniques to allow the measurement of scalar quantities throughout a three-dimensional volume in the flow. In one experiment, two closely-spaced parallel planes within a gas jet were illuminated simultaneously and imaged onto two intensified vidicon detectors. The measurement of the gas concentrations in the two flow planes enabled the three-component concentration gradient vector throughout a slice of the flow to be determined, so that some measure of the three-dimensionality of the flow field was obtained. For an instantaneous volumetric recording, measurements must be made at many more than two planes essentially simultaneously. To relax this requirement, a reproducible flow field was initially studied, so that the measurement of consecutive parallel flow planes could be made on different realizations of the same flow field. After this, a nonreproducible flow field was studied. A rotating mirror was used to rapidly sweep a laser illumination sheet through the flow volume and a fast data acquisition system was used to record the imaged flow planes in real-time. Time-resolved three-dimensional recordings of gas jets were thereby achieved.This paper presents a series of experiments designed to extend the capability of laser diagnostic techniques to allow the measurement of scalar quantities throughout a three-dimensional volume in the flow. In one experiment, two closely-spaced parallel planes within a gas jet were illuminated simultaneously and imaged onto two intensified vidicon detectors. The measurement of the gas concentrations in the two flow planes enabled the three-component concentration gradient vector throughout a slice of the flow to be determined, so that some measure of the three-dimensionality of the flow field was obtained. For an instantaneous volumetric recording, measurements must be made at many more than two planes essentially simultaneously. To relax this requirement, a reproducible flow field was initially studied, so that the measurement of consecutive parallel flow planes could be made on different realizations of the same flow field. After this, a nonreproducible flow field was studied. A rotating mirror was used ...