Application of an ultra-high-speed framing camera to aero-opticinvestigations,

摘要

Abstract: Characterization of small scale structures within high speed turbulent flow fields requires instrumentation that is capable of acquiring high speed data at rates exceeding one megahertz. From experimental studies performed by the Teledyne Brown Engineering (TBE) Experimental Aero-Optics Group in conjunction with SY Technology, it has been observed that structures within a high speed turbulent flow have a limited lifetime. With the development of the Ultranac computer controlled high speed camera, the collection of high speed images was possible. The camera was capable of 8 to 24 short sub-microsecond exposure times and fast MHz frequency frame rates, all of which was variable and could be set independently for each frame recorded by the camera. An application for this system was demonstrated using a collimated beam of HeNe laser light to record shadowgraphs of turbulent flow structures generated by TBE's Aero-Optic Simulator (AOS). Argon gas was exhausted at a low speed from one nozzle and neon gas was exhausted at a higher speed from the other nozzle to give a calculated shear layer flow velocity of approximately 450 m/s. Frame-by-frame comparisons were made and flow structures were observed to persist for periods on the order of a microsecond. Based on experience from this preliminary demonstration, improvements for future experiments have been suggested. These tests clearly demonstrate the potential of the Ultranac camera to aid in the characterization of high speed turbulent flows. !8