Investigation Of Impingement Region And Wall Jets Formed By The Interaction Of High Aspect Ratio Lift Jets And A Ground Plane

Author : Leighton Myers
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (927 download)

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Download or read book Investigation of the Flow-field of Two Parallel Round Jets Impinging Normal to a Flat Surface written by Leighton Myers and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The flow-field features of dual jet impingement were investigated through sub-scale model experiments. The experiments were designed to simulate the environment of a Short Takeoff, and Vertical Landing, STOVL, aircraft performing a hover over the ground, at different heights. Two different dual impinging jet models were designed, fabricated, and tested. The Generation 1 Model consisted of two stainless-steel nozzles, each with an exit diameter of approximately 12.7 mm. The front convergent nozzle was operated at NPR = 1.89 (Mj = 1.0), TTR = 1.0, while the rear C-D nozzle was generally operated over a range of NPR = 1.89 to NPR = 2.93 (Mj = 1.34), TTR = 1.0. The nozzles were embedded in a rectangular flat plate, referred to as the lift plate, which represented a generic lifting surface. The lift plate was instrumented with 36 surface pressure taps, which were used to examine the flow entrainment and recirculation patterns caused by varying the stand-off distance from the nozzle exits to a flat ground surface. The stand-off distance was adjusted with a sliding rail frame that the ground plane was mounted to. Typical stand-off distances, (ground plane separation), were H/D = 2 to 24.A series of measurements were performed with the Generation 1 model, in the Penn State High Speed Jet Aeroacoustics Laboratory, to characterize the basic flow phenomena associated with dual jet impingement. The regions of interest in the flow-field included the vertical jet plume(s), near impingement/turning region, and wall jet outwash. Other aspects of interest included the loss of lift (suckdown) that occurs as the ground plane separation distance becomes small, and azimuthal variation of the acoustic noise radiation. Various experimental methods and techniques were used to characterize the flow-field, including flow-visualization, pressure rake surveys, surface mounted pressure taps, laser Doppler velocimetry, and acoustic microphone arrays.A second dual impinging jet scale model, Generation 2, was designed and fabricated with a 50% increase in nozzle exit diameter. The primary design improvement is the ability to quickly and easily exchange the nozzles of the model. This allowed experiments to be performed with rapid-prototyped nozzles that feature more realistic geometry to that of tactical military aircraft engines. One such nozzle, which was designed and demonstrated by previous researchers to reduce jet noise in a free-jet, was incorporated into the model. The nozzle, featuring deflected seals, was installed in the Generation 2 model and its effect on suckdown was evaluated.