Effect of Reynolds number on the characteristics of coherent structures in free round jets

Date of Award


Publication Type

Master Thesis

Degree Name



Mechanical, Automotive, and Materials Engineering

First Advisor

Balachandar, Ramaswami (Civil & Environmental Engineering)


Engineering, Mechanical.



Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.


The effects of Reynolds number on the coherent structures in the near-exit region of a round free jet were examined. A quantitative analysis of the identified coherent structures was performed to understand the behaviour of the structures for different Reynolds numbers. High resolution PIV images were taken at three Reynolds numbers of 10,000, 30,000, and 55,000 up to a distance of 12 nozzle exit diameters in the axial direction in three fields-of-view. Two thousand images were acquired at each location in order to extract the statistical information about the behaviour of the flow. The POD technique was then applied to the PIV data to expose energy-containing structures. An automated vortex identification method was developed to identify the coherent structures. The structures so identified were quantified by their size, rotation, circulation and location. New insights into the jets were obtained by plotting statistical distributions of vortex properties.