Master of Science in Mechanical Engineering (MSME)


Mechanical Engineering

Document Type



Results from un-forced experiments conducted in the three-dimensional flow emanating from coaxial contoured nozzles with square cross section and parallel sides are presented and discussed. Two experiments were conducted with the inner to outer jet nominal velocity ratio equal to l=0.5 and l=1.5. The Reynolds number of the outer jet based on the hydraulic diameter of the outer nozzle exit was in both cases 16,000. A multi-position hot-wire anemometry method was used for measurements in the three-dimensional turbulent flow using a dual film sensor (X-probe). A methodology was developed and implemented to derive the mean-velocity components and Reynolds stresses corrected for velocity gradient effects. Axis switching, a phenomenon readily obtained with non-axisymmetric section nozzles, was observed as it evolves in the near-field using the three-dimensional flow maps obtained through this method. The overall entrainment was calculated from the measurements and compared to the case of equivalent circular coaxial nozzles under the same experimental conditions, where axis switching does not occur. The entrainment rate of the square geometry was found to clearly exceed the one of the circular geometry in the nozzle exit region. This brings evidence of overall mixing enhancement accomplished with the square nozzle. In addition to velocity spatial distribution, this study presents a spectral analysis that reveals the distribution of discrete modal amplitudes in three dimensions.



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Committee Chair

Dimitris Nikitopoulos