On a numerical study of atmospheric 2D and 3D—flows over a complex topography with forest including pollution dispersion

2007 ◽  
Vol 95 (9-11) ◽  
pp. 1424-1444 ◽  
Author(s):  
I. Sládek ◽  
T. Bodnár ◽  
K. Kozel
Keyword(s):  
Numerical Study ◽  
Complex Topography ◽  
Pollution Dispersion ◽  
3D Flows ◽  
2D And 3D

Numerical Study on Air-Reed Instruments With LES

2011 ◽  
Author(s):  
Kin’ya Takahashi ◽  
Masataka Miyamoto ◽  
Yasunori Ito ◽  
Toshiya Takami ◽  
Taizo Kobayashi ◽  
...  
Keyword(s):  
Numerical Study ◽  
Sound Field ◽  
Acoustic Analogy ◽  
Empirical Theory ◽  
Sound Sources ◽  
Aerodynamic Sound ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Semi Empirical ◽  
2D And 3D

The acoustic mechanisms of 2D and 3D edge tones and a 2D small air-reed instrument have been studied numerically with compressible Large Eddy Simulation (LES). Sound frequencies of the 2D and 3D edge tones obtained numerically change with the jet velocity well following Brown’s semi-empirical equation, while that of the 2D air-reed instrument behaves in a different manner and obeys the semi-empirical theory, so called Cremer-Ising-Coltman theory. We have also calculated aerodynamic sound sources for the 2D edge tone and the 2D air-reed instrument relying on Ligthhill’s acoustic analogy and have discussed similarities and differences between them. The sound source of the air-reed instrument is more localized around the open mouth compared with that of the edge tone due to the effect of the strong sound field excited in the resonator.

PREDICTION OF UNSTEADY STATES IN LID-DRIVEN CAVITIES FILLED WITH AN INCOMPRESSIBLE VISCOUS FLUID

2012 ◽  
Vol 23 (04) ◽  
pp. 1250030 ◽  
Author(s):  
FAYÇAL HAMMAMI ◽  
NADER BEN-CHEIKH ◽  
ANTONIO CAMPO ◽  
BRAHIM BEN-BEYA ◽  
TAIEB LILI
Keyword(s):  
Reynolds Number ◽  
Numerical Study ◽  
Three Dimensional ◽  
Staggered Grid ◽  
Three Dimensional Flow ◽  
Driven Cavity ◽  
Flow Evolution ◽  
2D And 3D ◽  
Benchmark Solutions ◽  
Good Agreement

In this work, a numerical study devoted to the two-dimensional and three-dimensional flow of a viscous, incompressible fluid inside a lid-driven cavity is undertaking. All transport equations are solved using the finite volume formulation on a staggered grid system and multi-grid acceleration. Quantitative aspects of two and three-dimensional flows in a lid-driven cavity for Reynolds number Re = 1000 show good agreement with benchmark results. An analysis of the flow evolution demonstrates that, with increments in Re beyond a certain critical value Rec, the steady flow becomes unstable and bifurcates into unsteady flow. It is observed that the transition from steadiness to unsteadiness follows the classical Hopf bifurcation. The time-dependent velocity distribution is studied in detail and the critical Reynolds number is localized for both 2D and 3D cases. Benchmark solutions for 2D and 3D lid-driven cavity flows are performed for Re = 1500 and 6000.

scholarly journals Numerical Study of 2D and 3D Separation Phenomena in the Dam-Break Flow Interacting with a Triangular Obstacle

2016 ◽  
Vol 60 (3) ◽  
pp. 159-166 ◽  
Author(s):  
Alexander Khrabry ◽  
◽  
Evgueni Smirnov ◽  
Dmitry Zaytsev ◽  
Valery Goryachev ◽  
...  
Keyword(s):  
Numerical Study ◽  
Dam Break ◽  
Dam Break Flow ◽  
2D And 3D

Thermal Lattice-Boltzmann Models (TLBM) for Compressible Flows

1998 ◽  
Vol 09 (08) ◽  
pp. 1247-1261 ◽  
Author(s):  
George Vahala ◽  
Pavol Pavlo ◽  
Linda Vahala ◽  
Nicos S. Martys
Keyword(s):  
Lattice Boltzmann ◽  
Compressible Flows ◽  
Temperature Dependent ◽  
Prandtl Numbers ◽  
Gauss Hermite Quadrature ◽  
Lattice Boltzmann Models ◽  
Thermal Lattice Boltzmann ◽  
3D Flows ◽  
2D And 3D ◽  
Rayleigh Benard

The progress and challenges in thermal lattice-Boltzmann modeling are discussed. In particular, momentum and energy closures schemes are contrasted. Higher order symmetric (but no longer space filling) velocity lattices are constructed for both 2D and 3D flows and shown to have superior stability properties to the standard (but lower) symmetry lattices. While this decouples the velocity lattice from the spatial grid, the interpolation required following free-streaming is just 1D. The connection between fixed lattice vectors and temperature-dependent lattice vectors (obtained in the Gauss–Hermite quadrature approach) is discussed. Some (compressible) Rayleigh–Benard simulations on the 2D octagonal lattice are presented for extended BGK collision operators that allow for arbitrary Prandtl numbers.

 Numerical tools to model seismic waves in unconsolidated and partially saturated granular media

2021 ◽  
Author(s):  
Kassem Asfour ◽  
Roland Martin ◽  
Ludovic Bodet ◽  
Didier El Baz ◽  
Bastien Plazolles ◽  
...  
Keyword(s):  
Numerical Study ◽  
Seismic Inversion ◽  
High Order ◽  
Signal Spectrum ◽  
Near Surface ◽  
Partially Saturated ◽  
Fluid Saturation ◽  
Phase Velocity Dispersion ◽  
2D And 3D ◽  
Surface Scale

<div><span>In order to accurately study the properties of partially saturated unconsolidated media at the near surface scale, or be able to image deeper structures through them, accurate 2D and 3D wave propagation numerical modelling tools are required. The rheology/mechanical properties of such media are frequently extremely complex (nonlinear, anisotropic, ... ), even when considered at dry state and of homogeneous mixture. Experimental observations (both at the laboratory and field scales) show that the seismic wave-field in unconsolidated granular materials remains difficult to interpret within standard methodological frameworks. We present here a numerical study aiming at exploring possible alternative forward modelling approaches to better extract information from recorded signals. <br></span></div><div><span> </span></div><div><span>We first present a finite volume method (Asfour et al. 2021) in which exact Riemann solvers are introduced. Solutions are compared to high-order finite-differences (Seismic_CPML code) and spectral finite element (SPECFEM code) solutions. A first series of synthetic cases is shown to benchmark the code at the hundred meters scale with a 100-300Hz wavelet source content. Another synthetic and more reallistic case is then presented with a medium affected by a steep nonlinear velocity gradient in depth, typical of an unconsolidated granular medium (as previously considered  at laboratory scale). For this model, a 1500Hz dominant frequency point source wavelet is considered and fluid saturation is also tested by applying a fluid-solid coupling. First arrival times and PSV-wave dispersion obtained from the different codes are compared. <br></span></div><div><span> </span></div><div><span>In a second step, and considering the real data recorded at the laboratory, we apply a more realistic source wavelet (obtained through signal spectrum ratio) and we perform parallelized high-order finite difference simulations (UNISOLVER code) to compare 2D and 3D elastic as well as poroelastic solutions on finely discretized meshes. Computed and observed data are compared. The poroelastic rheology provides better amplitudes in the seismograms and better exhibits some PSV modes in the phase velocity dispersion observations. Sensitivity kernels are also shown for the different rheologies. The different results obtained are now paving the way to seismic inversion at the near surface scale and to image shallow fluid/water saturated layers.</span></div>

Summer Episodes of Pollution Dispersion over the Coastal Area of Israel - A Numerical Study

1994 ◽  
pp. 45-52
Author(s):  
Joan Goldstein ◽  
Yakov Tokar ◽  
Yakov Balmor ◽  
Ed Glaser ◽  
Pinhas Alpert
Keyword(s):  
Coastal Area ◽  
Numerical Study ◽  
Pollution Dispersion
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