REDUCING THE NOISE INTENSITY OF SUBSONIC TURBULENT JETS USING NOISE-ATTENUATING DEVICES

Noise prediction of a subsonic turbulent round jet using the lattice-Boltzmann method.

The lattice-Boltzmann method (LBM) was used to study the far-field noise generated from a Mach, M(j)=0.4, unheated turbulent axisymmetric jet. A commercial code based on the LBM kernel was used to simulate the turbulent flow exhausting from a pipe which is 10 jet radii in length. Near-field flow results such as jet centerline velocity decay rates and turbulence intensities were in agreement wit...

Tonal dynamics and sound in subsonic turbulent jets

Acoustic waves trapped in the potential core of subsonic turbulent jets have recently been observed and explained by Towne et al. We show that these waves also radiate outside the jet, primarily into the upstream arc. We provide an experimental identification of the Mach-number dependence of the phenomenon, which indicates that the modes are active even when evanescent, probably due to turbulen...

Nonlinear interaction model of subsonic jet noise.

Noise generation in a subsonic round jet is studied by a simplified model, in which nonlinear interactions of spatially evolving instability modes lead to the radiation of sound. The spatial mode evolution is computed using linear parabolized stability equations. Nonlinear interactions are found on a mode-by-mode basis and the sound radiation characteristics are determined by solution of the Li...

Reducing luminance intensity can improve motion perception in noise

Visual perception generally improves under brighter environments. For instance, motion sensitivity is known to improve with luminance intensity especially at high temporal frequencies. However, the current study counter-intuitively shows that increasing luminance intensity can impair motion sensitivity in noise. Motion sensitivity was measured with and without noise added to a drifting Gabor pa...

Evaluation of the Advanced Subsonic Technology Program Noise Reduction Benefits