Turbulence effects on shaped booms: Propagation simulations using KZKFourier

Abstract

Upcoming X-59 aircraft flight tests as part of NASA’s Quesst Mission are expected to occur in a range of atmospheric conditions. Sensitivity of ground waveform acoustic metrics to turbulent perturbations through which booms propagate is a complicating factor in determining noise levels. A series of simulations through turbulence was executed using the KZKFourier model of Stout et al. to develop a database of results with which to expand functionality of NASA tools for estimating turbulence effects on shaped-boom ground waveforms. For 45 cases covering a seven-factor design space, multiple realizations of turbulence were generated to characterize statistical turbulence effects on levels of six acoustic metrics. Each individual simulation produced over one thousand waveforms across a virtual microphone array. Different measures were used to evaluate refinement of results with increasing number of simulations. Data suggest that mean effects and variability were most strongly influenced by propagation distance as well as velocity fluctuation intensity, and that, although local increases in acoustic metrics were common, the overall average result in all cases was a reduction in metric levels. Sensitivity of acoustic metrics varied, with mean reductions in Perceived Level occurring in the range of up to 2 dB across the 45 cases.