Experiments in a Large Boundary Layer Wind Tunnel: Propagation of Noise through the Turbulent Boundary Layer

Abstract

A series of acoustic propagation experiments was conducted in the University of Florida Boundary Layer Wind Tunnel (UFBLWT) to investigate tornadic infrasound propagation in the turbulent atmosphere. A synthetic acoustic wave was generated within a boundary layer wind field using a speaker, and distorted by the surrounding turbulent atmosphere as it propagated along the UFBLWT fetch where it was measured by an acoustic microphone 22 m downwind of the speaker. The wind tunnel operating speed and the configuration of the mechanical turbulence generating roughness elements were varied between experiments to alter the turbulence characteristics and thus the distortion of the acoustic wave. The wind field turbulence data were obtained by three Cobra probes mounted on an actuated and automated gantry. The turbulence-induced distortion of the acoustic wave was captured by analyzing the signal at its source and as-measured downwind. Data were characterized, organized, and curated into four stages.