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Journal of Flow Visualization and Image Processing
SJR: 0.161 SNIP: 0.312 CiteScore™: 0.1

ISSN Print: 1065-3090
ISSN Online: 1940-4336

Journal of Flow Visualization and Image Processing

DOI: 10.1615/JFlowVisImageProc.2018027034
pages 33-46

STRUCTURE OF UNDEREXPANDED SUPERSONIC JETS FROM AXISYMMETRIC LAVAL NOZZLES

Hiroaki Maeda
University of Kitakyushu, 1-1, Hibikino, Wakamatsu-ku, Kitakyushu, Fukuoka, 808-0135 Japan
H. Fukuda
University of Kitakyushu, 1-1, Hibikino, Wakamatsu-ku, Kitakyushu, Fukuoka, 808-0135 Japan
K. Kubo
Meisei Electric Co., Ltd., 2223 Naganumamachi, Isesaki-shi, Gunma, 372-8585 Japan
Shinichiro Nakao
University of Kitakyushu, 1-1, Hibikino, Wakamatsu-ku, Kitakyushu, Fukuoka, 808-0135 Japan
D. Ono
University of Kitakyushu, 1-1, Hibikino, Wakamatsu-ku, Kitakyushu, Fukuoka, 808-0135 Japan
Yoshiaki Miyazato
University of Kitakyushu, 1-1, Hibikino, Wakamatsu-ku, Kitakyushu, Fukuoka, 808-0135 Japan

ABSTRACT

The rainbow schlieren deflectometry is combined with the computed tomography to obtain three-dimensional density fields of a shock-containing free jet issued from a Laval nozzle with a design Mach number of 1.5. Experiments have been performed at a nozzle operating pressure ratio of 4.0, where the nozzle is operated at a slightly underexpanded condition. Multidirectional rainbow schlieren pictures of the jet can be acquired by rotating the nozzle about its longitudinal axis in equal angular intervals and the three-dimensional density fields are reconstructed by two types of image analyses for experimental data. One is a data processing procedure based on the Abel inversion algorithm, and the other is that with the convolution back-projection algorithm. It is found that excellent quantitative agreement is reached between the jet three-dimensional density fields reconstructed from both algorithms. The present rainbow schlieren technique is found to be significantly effective to examine a fine shock-cell structure of the shock-containing jet and makes it possible to provide experimental data with high accuracy and reliability on the jet density field.