A linearized Euler finite-difference time-domain sound propagation model with terrain-following coordinates

Heimann, Dietrich; Karle, Regina

doi:10.1121/1.2200139

Cited by 26 publications

(14 citation statements)

References 16 publications

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“…This choice was justified in view of the reduction in computing time by a factor 8 when using the coarser grid. Surface-following coordinates [11] or curvilinear FDTD grids [12] could be an alternative.…”

Section: Finite Differences Time Domain Modelling Of the Acoustic Scamentioning

confidence: 99%

Finite difference time domain modelling of sound scattering by the dynamically rough surface of a turbulent open channel flow

et al. 2016

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a b s t r a c tThe problem of scattering of airborne sound by a dynamically rough surface of a turbulent, open channel flow is poorly understood. In this work, a laser-induced fluorescence (LIF) technique is used to capture accurately a representative number of the instantaneous elevations of the dynamically rough surface of 6 turbulent, subcritical flows in a rectangular flume with Reynolds numbers of 10; 800 6 Re 6 47; 300 and Froude numbers of 0:36 6 Fr 6 0:69. The surface elevation data were then used in a finite difference time domain (FDTD) model to predict the directivity pattern of the airborne sound pressure scattered by the dynamically rough flow surface. The predictions obtained with the FDTD model were compared against the sound pressure data measured in the flume and against that obtained with the Kirchhoff approximation. It is shown that the FDTD model agrees with the measured data within 22.3%. The agreement between the FDTD model and stationary phase approximation based on Kirchhoff integral is within 3%. The novelty of this work is in the direct use of the LIF data and FDTD model to predict the directivity pattern of the airborne sound pressure scattered by the flow surface. This work is aimed to inform the design of acoustic instrumentation for non-invasive measurements of hydraulic processes in rivers and in partially filled pipes.

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Section: Finite Differences Time Domain Modelling Of the Acoustic Scamentioning

confidence: 99%

Finite difference time domain modelling of sound scattering by the dynamically rough surface of a turbulent open channel flow

et al. 2016

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“…In cases of high variations of the terrain or of the medium properties, however, the parabolic approximation in PE is not valid. In recent years, FDTD [14][15][16] models have drawn substantial interest due to their ability to handle complex topography, meteorology and complicated phenomena such as scattering from buildings and trees or dynamic turbulence fields. The treatment of finite ground impedance and the timeconsuming calculations-in order to get accurate resultsare the main drawbacks of these models.…”

Section: Introductionmentioning

confidence: 99%

Determination of equivalent sound speed profiles for ray tracing in near-ground sound propagation

Prospathopoulos

Voutsinas

2007

The Journal of the Acoustical Society of America

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The determination of appropriate sound speed profiles in the modeling of near-ground propagation using a ray tracing method is investigated using a ray tracing model which is capable of performing axisymmetric calculations of the sound field around an isolated source. Eigenrays are traced using an iterative procedure which integrates the trajectory equations for each ray launched from the source at a specific direction. The calculation of sound energy losses is made by introducing appropriate coefficients to the equations representing the effect of ground and atmospheric absorption and the interaction with the atmospheric turbulence. The model is validated against analytical and numerical predictions of other methodologies for simple cases, as well as against measurements for nonrefractive atmospheric environments. A systematic investigation for near-ground propagation in downward and upward refractive atmosphere is made using experimental data. Guidelines for the suitable simulation of the wind velocity profile are derived by correlating predictions with measurements.

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“…(4) Elevate the DSM points to their heights. (5) Elevate the boundary and building outline segments by extrapolation of the heights of the DSM points extracted in step (1). The extrapolation technique is explained in Sect.…”

Section: Reconstruction Of the Groundmentioning

confidence: 99%

“…However, the study was conceptual in that the frequency target of the simulation was as low as approximately 30 Hz owing to the use of a finite-difference grid of 1 m spacing forced by the limitation of the technique. Specifically, the applicability of the geometry reconstruction technique was limited by the following points: (1) The technique performs staircasing of the original building geometry with alignment to a grid system of hard-coded 1 m spacing. The staircasing prohibits accurate reproduction of the original geometry, especially required for high-frequency simulations.…”

Section: Introductionmentioning

confidence: 99%

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Geometry reconstruction and mesh generation techniques for acoustic simulations over real-life urban areas using digital geographic information

Oshima

Hiraguri

Imano

2014

Acoust. Sci. & Tech.

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With the recent progresses in computer performance and simulation techniques, it is becoming feasible to apply full three-dimensional wave-based numerical simulation techniques to large-scale problems of real-life sound propagation outdoors. In the present paper, a reconstruction technique for real-life urban geometries with full reproduction of the roof shapes and for the ground profiles using digital geographic information is presented. Also, a generation technique for the uniform rectilinear grid used in finite-difference time-domain simulations is presented. The types of geographic dataset used for the reconstruction are a digital surface model and a two-dimensional building outline map. For comparison, another geometry with flat building roofs, which is the type of geometry used in former noise-mapping studies using empirical models, is created. Comparison of the results of finitedifference time-domain acoustic simulations performed over the geometries shows sound pressure level differences above and behind buildings. The maximum level difference of 10 dB in magnitude indicates the necessity of proper reconstruction of the roof shapes in real-life urban acoustic simulations.

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A linearized Euler finite-difference time-domain sound propagation model with terrain-following coordinates

Cited by 26 publications

References 16 publications

Finite difference time domain modelling of sound scattering by the dynamically rough surface of a turbulent open channel flow

Finite difference time domain modelling of sound scattering by the dynamically rough surface of a turbulent open channel flow

Determination of equivalent sound speed profiles for ray tracing in near-ground sound propagation

Geometry reconstruction and mesh generation techniques for acoustic simulations over real-life urban areas using digital geographic information

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