Contribution
Influence on the Sound Field of the Boundary Layer Interface and Low-Level Jet Modelling in a Conventionally Neutral Boundary Layer
* Presenting author
Abstract:
The variation of wind and temperature with height determines how sound propagates over large distances. This variation is often described by a logarithmic profile, which is a suitable description in a truly neutral boundary layer. However, the boundary layer is more often only conventionally neutral. In this case, the profile has a characteristic nose (low level jet, LLJ) the results in a wind speed and gradient larger than what is predicted by a logarithmic profile. In this work we investigate the effect that this nose has on the turning point of the acoustic waves when they go from upward to downward propagation due to the inhomogeneous medium through theory and simulations using the Crank-Nicholson Parabolic Equation. Furthermore, the interface between the boundary layer, considered in this study, and the free atmosphere aloft can also have an impact on the sound field on the ground. In this study, we also investigate this effect, considering an abrupt and smooth interface between these two layers and analyzing the corresponding sound fields on the ground through simulations.