A generalized polar coordinate method for sound propagation over large-scale irregular terrain

2010 ◽  
Vol 128 (5) ◽  
pp. 2573-2580 ◽  
Author(s):  
Santosh Parakkal ◽  
Kenneth E. Gilbert ◽  
Xiao Di ◽  
Henry E. Bass
Keyword(s):  
Large Scale ◽  
Sound Propagation ◽  
Coordinate Method ◽  
Irregular Terrain ◽  
Polar Coordinate

scholarly journals Atmospheric Sound Propagation Over Large-Scale Irregular Terrain

2014 ◽  
Vol 61 (2) ◽  
pp. 369-397 ◽  
Author(s):  
Martin Almquist ◽  
Ilkka Karasalo ◽  
Ken Mattsson
Keyword(s):  
Large Scale ◽  
Sound Propagation ◽  
Irregular Terrain

scholarly journals Vertical and slanted sound propagation in the near-ground atmosphere : amplitude and phase fluctuations

2021 ◽  
Author(s):  
Matthew Kamrath ◽  
Vladimir Ostashev ◽  
D. Wilson ◽  
Michael White ◽  
Carl Hart ◽  
...  
Keyword(s):  
Large Scale ◽  
Sound Propagation ◽  
Microphone Arrays ◽  
Small Scale ◽  
Sound Sources ◽  
Phase Fluctuations ◽  
Turbulent Eddies ◽  
Low Altitude ◽  
Detection And Localization ◽  
Large Eddies

Sound propagation along vertical and slanted paths through the near-ground atmosphere impacts detection and localization of low-altitude sound sources, such as small unmanned aerial vehicles, from ground-based microphone arrays. This article experimentally investigates the amplitude and phase fluctuations of acoustic signals propagating along such paths. The experiment involved nine microphones on three horizontal booms mounted at different heights to a 135-m meteorological tower at the National Wind Technology Center (Boulder, CO). A ground-based loudspeaker was placed at the base of the tower for vertical propagation or 56m from the base of the tower for slanted propagation. Phasor scatterplots qualitatively characterize the amplitude and phase fluctuations of the received signals during different meteorological regimes. The measurements are also compared to a theory describing the log-amplitude and phase variances based on the spectrum of shear and buoyancy driven turbulence near the ground. Generally, the theory correctly predicts the measured log-amplitude variances, which are affected primarily by small-scale, isotropic turbulent eddies. However, the theory overpredicts the measured phase variances, which are affected primarily by large-scale, anisotropic, buoyantly driven eddies. Ground blocking of these large eddies likely explains the overprediction.

An Advanced Numerical Model for Assessing 3-D Wind Fields

2007 ◽  
Author(s):  
Darrell W. Pepper ◽  
Xiuling Wang
Keyword(s):  
High Resolution ◽  
Large Scale ◽  
Element Model ◽  
Integral Function ◽  
Wind Fields ◽  
Local Flow ◽  
Irregular Terrain ◽  
Topographic Features ◽  
Element Size ◽  
The Difference

An h-adaptive mass consistent finite element model (FEM) is developed for constructing 3-D wind fields over irregular terrain. The h-adaptive FEM allows the element size to be changed dynamically according to local flow and topographic features. The mesh is refined and unrefined to satisfy preset error criteria. Localized high resolution wind fields can be constructed. The FEM model uses a variational method in an integral function that minimizes the variance of the difference between the observed and analyzed variable. Simulation results are presented for constructing 3-D wind fields for two regions in Nevada. The method appears promising for accurately depicting large scale wind fields, especially where high resolution is needed to capture rapidly changing flows associated with local topographic features.

Study on Machining Accuracy of Scroll Shape Workpiece with Polar Coordinate Method

2002 ◽  
Vol 2002.39 (0) ◽  
pp. 255-256
Author(s):  
Hiroyasu IWABE ◽  
Masahide KOBAYASHI ◽  
Hideaki MATSUHASHI
Keyword(s):  
Machining Accuracy ◽  
Coordinate Method ◽  
Polar Coordinate
Sign in / Sign up

Export Citation Format

Share Document