Dissipation rate estimation in a rectangular shaped test section with periodic structure at the walls

Abstract

An experimental study of turbulent flow concerning the characterization of turbulence by two-point correlation and estimations of the turbulent dissipation rate is presented. The fluid used is deionized water and the test section used was a square shaped channel of 24mm by 30mm on the cross section with a length of 1m. The test section also presented periodic baffle structure at two of the walls for enhancing and maintaining turbulence. The study consisted in the measurement of the velocities at different positions of the channel using Laser Doppler Velocimetry instrument (LDV), the velocity measurement obtained were used for estimating two point correlations using the Taylor's frozen hypothesis. Finally, the results from the two-point correlation were used for estimating the turbulent dissipation rate. Considering the difference in the methods for calculating the dissipation rate, a comparison of the accuracy of each method is presented. It was found that the methods presented in this work showed similar results and trends of the dissipation rate with respect to changes in flow condition and distance to the channel walls. However, better accuracy was obtained by estimating the dissipation rate using the second order structure function and the Kolmogorov's two-third law.