Fourier transform evaluation and numerical modeling of fluid flow in a Laval nozzle

Abstract

A new system for characterizing the flow delivered by a Laval nozzle in different stream configurations has been designed, developed, settled and tested. An optical module (Mach-Zehnder interferometer), an acquisition module (CMOS camera) and a processing module (Fourier Transform Phase Difference Method) have been integrated and assembled in order to obtain the instantaneous optical phase distribution along the gas flow. An additional postprocessing numerical stage provides gradient and Laplacian information of the optical phase distribution and allows a complete modeling of the fluid flow. In this work the main results, advantages and limitations of the metrological protocol related with a detailed measurement campaign are presented. Also the analysis of the obtained optical phase difference distribution is compared with results given by a tailored processing numerical stage.