Experimental Characterization of Turbulent Flow Around Cylinder Arrays

This research was done as part of an effort to develop alternative fire suppressant technologies for aircraft engine nacelles. A circular cylinder array was designed, built, and placed in the AFIT roll-around low speed wind tunnel to model generic clutter inside an engine nacelle. A turbulence grid was fabricated to enable measurements of the effects of turbulence level, independent of airspeed, on the flow over different model configurations. The wind tunnel test section was 12 inches wide x 12 inches high x 24 inches long. Pressure differential measurements were taken on various cylinder configurations. The configurations included one cylinder as well as one, two, and three arrays of cylinders. Half diameter spacing was used for two and three cylinder cases, as well as an additional case at a two-diameter spacing with the three array configuration. All conditions were tested with and without the turbulence grid placed at the front of the test section. Pressure differential measurements were taken at 15-degree increments from 0 degrees - 180 degrees on the circumference of an upstream cylinder, centered vertically on the array. Hot-wire measurements were taken with and without the turbulence grid to determine airspeed and the effect of turbulence intensity generated by the grid on the wake profile. Also, vertical traverse data was taken with the hot-wire to determine airflow characteristics behind two configurations, both with and without a turbulence grid. The first had only one cylinder installed while the second was done with three arrays spaced at a half-diameter length. Pressure and velocity measurements were used to investigate the effects caused by the upstream turbulence grid