Laser Velocimeter Measurements in Turbulent and Mixing Flows.

Abstract : An experimental facility has been designed and constructed to investigate the application of laser Doppler velocimetry to turbulent and mixing flows. Major features of the optical system include variable fringe spacing, variable beam diameter in the probe volume, precise control of the beam intersection point relative to the beam waist, provision for frequency shifting of one or both input beams, the ability to easily rotate the instrument about the optical axis, the ability to traverse the probe volume in x, y and z, and the control of the polarization of light entering the beam divider. The flow system provides subsonic air flow over a rearward facing step simulating a dump combustor. The data collection and storage system consists of a high speed burst processor, a dedicated microcomputer for high speed data collection, and a floppy disc for data storage. Data processing is done on a CDC6500 computer connected to the system via a phone line. The system will be used to measure and document measuring biases in an LDV system in highly turbulent and mixing flows. (Author)