A data analysis system for unsteady turbulence measurements

Abstract

data analysis system has been developed to analyze unsteady turbulence measurements obtained in the boundary layer of an airfoil subjected to periodic turbulent pulse disturbances such as in a propeller slipstream. Specific algorithms for analyzing the non-stationary data are identified, developed and implemented. Where alternate algorithms are developed, each is evaluated and the best method is recommended based on specified criteria. The statistical parameters used to characterize the unsteady turbulent boundary layer include the non-stationary mean velocity, turbulence intensity, power spectral density and the autocorrelation and cross correlation functions. Since the data are periodic, both ensemble averaging and special non- stationary empirical model techniques are employed. Each of the algorithms has been implemented in the FORTRAN language and examples are presented using representative test case data.