Experimental study of the propagation of a far-field disturbance in the turbulent flow through square array tube banks

Abstract

This paper presents the experimental analysis of the propagation of a disturbance with a fixed frequency in the incidence velocity of the cross flow through a tube bank, and its influence on the velocity fluctuations inside the bank. The disturbance is generated outside the bank by vortex shedding from an obstacle. The tube banks investigated had square arrangement and aspect ratio P/D = 1.60 and 1.26. Air was the working fluid. Measurements were performed with hot wires. Behavior of fluctuating velocities is described by means of autospectral density. The results show that the frequency of the disturbance remains unchanged as it passes through the bank, and subsists until the 4th row in spite of the high turbulence intensities and of the fact that flow velocity inside the bank varies with the position. This fact indicates that external excitations can be transferred to the solid boundaries of the bank maintaining their original frequency. Continuous Wavelet Transforms of the signals show that, in time domain, the frequency of the disturbance has an almost steady behavior.