Study of the effect of excitation on a circular air jet

Abstract

The deficiency in the clear understanding of the turbulent jet structure. despite its important speculative role. provided the motivation for the present study. Somecharacteristics of circular jet with and without excitation were investigated along with the calculation of some integral and differential variables. Constant temperature hot wire anemometer responses and First Fourier Transform (FFT) analyzer traces have been analyzed in order to get an articulate picture of the jet response to pure. tone acoustic excitation. The effect of jet column mode and shear layer mode excitation are also considered in this research. The results show that the longitudinal turbulence intensities in the centerline and different axial distances parallel to the centerline can both be enhanced and suppressed by inducing different conditions of excitation. The centerline turbulence intensities started to be enhanced at lower excitation frequency and after reaching the maximum started to decrease with further increase in excitation frequencies. However on a line parallel and half diameter apart from centerline. suppression is observed for all excitation frequencies. Both in enhancement and suppression of turbulence the effect of jet column mode excitation is nearly stable while that of shear layer mode excitation is unstable.