Effect of aspect ratio on mean flow characteristics of cruciform orifice jet
Aircraft Engineering and Aerospace Technology
ISSN: 0002-2667
Article publication date: 8 December 2023
Issue publication date: 6 February 2024
Abstract
Purpose
The purpose of this study reports the effects of aspect ratio (AR) on mean flow characteristics of the cruciform orifice jet.
Design/methodology/approach
The aspect ratio is the height-to-width ratio of the lobe of the cruciform shape. The aspect ratios considered are 0.25, 0.5, 0.75, 1, 2, 3 and 4. The turbulent jet flow is issued through an orifice being fitted to the jet tunnel facility. The velocity measurements are recorded with the help of pitot-static tube connected to a digital manometer setup. The Reynolds number calculated using the equivalent diameter 50.46 × 10–3 m and exit velocity 51.23 m/s was 1.75 × 105. Based on the experimental data, the streamline velocity decay plots, the potential core length (PCL), mean velocity profiles and velocity half widths were plotted, and discussions were made based on the measured data. A smoke-based flow visualization was carried out at moderate Reynolds number 5396.
Findings
The PCL remains almost constant for the aspect ratio 0.25:1 and then starts decreasing for the aspect ratio 1:4. The decrease in PCL indicates improved mixing. The off-center peaks are found along the major axis in mean velocity profiles for almost all cruciform jets. More than one axis switching occurs and can be identified by the crossover points. The location of the first crossover point shifts forward, and the second crossover point shows an oscillating trend. The flow visualization exhibits the jet evolution, and the distance up to which the jet maintains the cruciform shape is increased with the aspect ratio.
Research limitations/implications
The experiments are limited to air in air jet under isothermal conditions.
Social implications
The cruciform orifices can be used as fuel injectors and in air-conditioning systems, thereby improving efficiency and energy usage.
Originality/value
The aspect ratio effects on PCL and axis switching are used to explain the mixing characteristics. Flow visualization was also used to support the discussion.
Keywords
Acknowledgements
B.T.K. acknowledges the usage of the following facilities, jet tunnel in Aerodynamics Laboratory, machine shop for machining the orifice plates, Advanced Computing Laboratory for documentation work and impingement jet facility for flow visualization. K.B.T. expresses heartfelt thanks to the supervisor and lab assistants of the Aerospace Engineering Hangar for the assistance in conducting the experiment. The authors also thank the students Mr Lalit V. and Mr Promoth K.K. for their help during flow visualization experiment. The authors also thank Dr M Vignesh Kumar (Assistant Professor) for the preparation of the Metal Orifice Plates.
Citation
S., R.K., Sadrani, N. and B.T., K. (2024), "Effect of aspect ratio on mean flow characteristics of cruciform orifice jet", Aircraft Engineering and Aerospace Technology, Vol. 96 No. 1, pp. 144-150. https://doi.org/10.1108/AEAT-08-2022-0205
Publisher
:Emerald Publishing Limited
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