Quantitative visualization of steady and unsteady flows using spark velocimetry

This paper describes the usefulness, limitations, and potential applications of spark velocimetry to complex flows in fluid machinery. Spark velocimetry uses high‐voltage high‐frequency sparks to successively illuminate a column of air particles and thus map out a complex velocity field. This work applied spark velocimetry to a two‐dimensional boundary layer, a three‐dimensional horseshoe vortex boundary layer, and boundary layers on the suction surface of a rotor blade in steady flow and in rotating stall. Measurements made in a two‐dimensional boundary layer compared favorably with measurements taken using a total pressure probe. The measurements in the horseshoe vortex showed the types of primary and secondary flow expected. The velocity profile of the boundary layer on a rotor blade was shown in both unstalled and stalled flow. The spark velocimetry method was shown to be a very useful measurement tool for three‐dimensional and unsteady flows with some limitations.