Entrainment and mixing of turbulent jets in co-flow

Kilcoyne, David Thomas; Hugger, Craig Peter; Vassilieva, Maria I.

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Entrainment and mixing of turbulent jets in co-flow

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The main focus of this project was to study the behavior of turbulent, axisymmetric jets in co-flow. There were two primary goals. The first was to compare the techniques of jet seeding to co-flow seeding using smoke. The second goal was to study the technique of seeding the jet or the co-flow with solid particles. To accomplish this a particle generator was designed and manufactured. To obtain flow visualization, the seeded material of the jet or co-flow was illuminated with a laser sheet. Seeding material included mineral oil smoke and aluminum oxide particles. The illumination of the particles allowed an image of the flow to be taken with a digital camera. These images were analyzed using WiT image processing software. An existing wind tunnel developed for co-flow was used for this project. The wind tunnel consisted of a contraction section, jet injection system and test section. The test section had a 6" x 6" (15.24 cm x 15.24 cm) cross section and was 23" (58.42 cm) in height. The contraction area ratio was 6:1, which corresponded to a 15" x 15" (38.1 cm x 38.1 cm) cross section for the contraction nozzle inlet. To expand the capabilities of the wind tunnel, modifications to the previous plumbing and test section design were made. The plumbing was redesigned to allow both jet and co-flow seeding by either a smoke generator or a particle generator. The test section height was increased to eliminate effects on the gas flow by the ventilation system. Experimental results showed that jet seeding proved to be a better method for flow visualization than co-flow seeding. Self-similarity of radial concentration profiles for jet seeding was observed as far as 100 nozzle diameters downstream for some cases, whereas the co-flow seeded profiles rarely displayed any selfsimilarity for distances greater than 50 nozzle diameters downstream. Seeding the jet with solid particles of aluminum oxide appears to be an acceptable technique for flow visualization. While a limited amount of data was obtained, it was concluded that this seeding technique, with improvements, could work as well as the smoke seeding technique.

This report represents the work of one or more WPI undergraduate students submitted to the faculty as evidence of completion of a degree requirement. WPI routinely publishes these reports on its website without editorial or peer review.

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