A MULTI-SCALE APPROACH FOR THE ANALYSIS OF PROPER SAMPLED DATA SCALE IN HOT-WIRE EXPERIMENT OF SQUARE DUCT FLOW

Without rational criteria to determine the Proper Sampled Data Scale(PSDS),it would result in the expense of the too much unnecessary processing time and storage space in turbulent experiments.A novel approach for PSDS was established herein on the basis of turbulence theory and statistics.The specific procedure was given by using wavelet tools.A case study to prove the reliability and rationality of this approach was reported,where the sampled hot-wire data were from the experiment of square duct flow and turbulence kinetic energy was selected as the concerned turbulence parameter.It is shown that 220 quantities of the sampled data are enough to analyze turbulence kinetic energy in the present experiment.The PSDSs of three turbulence parameters at different Reynolds numbers(Re =4.60×104,7.68×104 and 1.23×105)were studied.The results illustrate that the PSDSs increase with the increment of the Reynolds number and the order of concerned turbulence parameter.