Turbulence measurements by particle imaging velocimetry

Abstract

Statistical parameters of the flow velocity are often appropriate in the description of nonstationary flows. Derivation of such data from step by step scanning of Particle Imaging Velocimetry (PIV) records is cumbersome and time-consuming. It is proposed to obtain statistical quantities by processing large fields in such records in a single step. Principal relations are derived leading to an evaluation of the autocorrelation function of the PIV image. This is obtained by combining optical and electronic processing. The range of applicability is extended greatly by introducing an image doubling method. This is demonstrated by measurement of the degree of turbulence in low turbulence wind tunnel flows.Statistical parameters of the flow velocity are often appropriate in the description of nonstationary flows. Derivation of such data from step by step scanning of Particle Imaging Velocimetry (PIV) records is cumbersome and time-consuming. It is proposed to obtain statistical quantities by processing large fields in such records in a single step. Principal relations are derived leading to an evaluation of the autocorrelation function of the PIV image. This is obtained by combining optical and electronic processing. The range of applicability is extended greatly by introducing an image doubling method. This is demonstrated by measurement of the degree of turbulence in low turbulence wind tunnel flows.