Aktív rács keltette turbulencia jellemzőinek meghatározása hődrótos adatok alapján

Abstract

This paper deals with the determination of several turbulence quantities in case of nearly isotropic, homogeneous grid turbulence. Grids placed in wind tunnels upstream of the test section are used to produce flow with roughly isotropic and homogeneous, decaying turbulence. Such flows then can be applied for measurements which demand flow with predetermined turbulent properties. Therefore first, the characterization of the achievable turbulence has to be carried out. For this purpose, the so-called constant-temperature anemometry was applied. The time series of instantaneous velocity-component samples downstream of a novel type active grid were processed in MATLAB® script made by us for this purpose. By means of the script, the following turbulent properties can be derived: turbulence intensity in one and three dimensions, turbulence kinetic energy, isotropy ratio, integral time-scale, turbulence energy spectra, dissipation rate of turbulent kinetic energy, Kolmogorov microscales, Taylor microscale, Turbulence Reynolds number, Taylor-Reynolds number. The longitudinal energy spectra at different setups of our novel active grid is presented, as well.