Simulating the Envelope of Scalar Waves in 2D Random Media Having Power-Law Spectra of Velocity Fluctuation

2003 ◽  
Vol 93 (1) ◽  
pp. 240-252 ◽  
Author(s):  
T. Saito
Keyword(s):  
Power Law ◽  
Velocity Fluctuation ◽  
Random Media ◽  
Scalar Waves

scholarly journals FRONT PROPAGATION IN RANDOM MEDIA: FROM EXTREMAL TO ACTIVATED DYNAMICS

2002 ◽  
Vol 13 (06) ◽  
pp. 751-757 ◽  
Author(s):  
RUNE SKOE ◽  
DAMIEN VANDEMBROUCQ ◽  
STÉPHANE ROUX
Keyword(s):  
Low Temperature ◽  
Numerical Simulations ◽  
Power Law ◽  
Random Environment ◽  
Random Media ◽  
Front Propagation ◽  
Force Distribution ◽  
Zero Temperature ◽  
Arrhenius Behavior ◽  
Very Low Temperature

Front propagation in a random environment is studied close to the depinning threshold. At zero temperature we show that the depinning force distribution exhibits a universal behavior. This property is used to estimate the velocity of the front at very low temperature. We obtain a Arrhenius behavior with a prefactor depending on the temperature as a power law. These results are supported by numerical simulations.

scholarly journals Numerical and Experimental Investigation of the Neutral Atmospheric Surface Layer

2007 ◽  
Vol 64 (1) ◽  
pp. 137-156 ◽  
Author(s):  
Philippe Drobinski ◽  
Pierre Carlotti ◽  
Jean-Luc Redelsperger ◽  
Valery Masson ◽  
Robert M. Banta ◽  
...  
Keyword(s):  
Surface Layer ◽  
Power Law ◽  
Velocity Fluctuation ◽  
Scale Model ◽  
Order Moment ◽  
Doppler Lidar ◽  
Mean Flow ◽  
Surface Exchange ◽  
Near Surface ◽  
Sonic Anemometers

Abstract This study combines the experimental measurements with large-eddy simulation (LES) data of a neutral planetary boundary layer (PBL) documented by a 60-m tower instrumented with eight sonic anemometers, and a high-resolution Doppler lidar during the 1999 Cooperative Atmospheric and Surface Exchange Study (CASES-99) experiment. The target of the paper is (i) to investigate the multiscale nature of the turbulent eddies in the surface layer (SL), (ii) to explain the existence of a −1 power law in the velocity fluctuation spectra, and (iii) to investigate the different nature of turbulence in the two sublayers within the SL, which are the eddy surface layer (ESL; lower sublayer of the SL lying between the surface and about 20-m height) and the shear surface layer (SSL; lying between the ESL top and the SL top). The sonic anemometers and Doppler lidar prove to be proper instruments for LES validation, and in particular, the Doppler lidar because of its ability to map near-surface eddies. This study shows the different nature of turbulence in the ESL and the SSL in terms of organized eddies, velocity fluctuation spectra, and second-order moment statistics. If quantitative agreement is found in the SSL between the LES and the measurements, only qualitative similarity is found in the ESL due to the subgrid-scale model, indicating that the LES captures part of the physics of the ESL. The LES helps explain the origin of the −1 power-law spectral subrange evidence in the velocity fluctuation spectra computed in the SL using the CASES-99 dataset: strong interaction between the mean flow and the fluctuating vorticities is found in the SL, and turbulent production is found to be larger than turbulent energy transfer for k1z > 1 (k1 being the longitudinal wavenumber and z the height), which is the condition of the −1 power-law existence.

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