Turbulent scalar fluxes from a generalized Langevin model: Implications on mean scalar mixing and tracer particle dispersion

2021 ◽  
Vol 33 (3) ◽  
pp. 035101
Author(s):  
Bertrand Naud ◽  
Dirk Roekaerts
Keyword(s):  
Tracer Particle ◽  
Particle Dispersion ◽  
Scalar Mixing ◽  
Langevin Model ◽  
Scalar Fluxes

scholarly journals Penetrative convection in stratified fluids: velocity and temperature measurements

2006 ◽  
Vol 13 (3) ◽  
pp. 353-363 ◽  
Author(s):  
M. Moroni ◽  
A. Cenedese
Keyword(s):  
Feature Tracking ◽  
Tracer Particle ◽  
Mixing Layer ◽  
Pollutant Dispersion ◽  
Particle Dispersion ◽  
Layer Growth ◽  
Laboratory Model ◽  
Penetrative Convection ◽  
Stratified Lakes

Abstract. The flux through the interface between a mixing layer and a stable layer plays a fundamental role in characterizing and forecasting the quality of water in stratified lakes and in the oceans, and the quality of air in the atmosphere. The evolution of the mixing layer in a stably stratified fluid body is simulated in the laboratory when "Penetrative Convection" occurs. The laboratory model consists of a tank filled with water and subjected to heating from below. The methods employed to detect the mixing layer growth were thermocouples for temperature data and two image analysis techniques, namely Laser Induced Fluorescence (LIF) and Feature Tracking (FT). LIF allows the mixing layer evolution to be visualized. Feature Tracking is used to detect tracer particle trajectories moving within the measurement volume. Pollutant dispersion phenomena are naturally described in the Lagrangian approach as the pollutant acts as a tag of the fluid particles. The transilient matrix represents one of the possible tools available for quantifying particle dispersion during the evolution of the phenomenon.

Diffusion in stably stratified turbulence

1996 ◽  
Vol 328 ◽  
pp. 253-269 ◽  
Author(s):  
Y. Kimura ◽  
J. R. Herring
Keyword(s):  
Reynolds Numbers ◽  
Eddy Diffusion ◽  
Stable Stratification ◽  
Particle Dispersion ◽  
Stratified Flows ◽  
Stratified Turbulence ◽  
Low Reynolds Numbers ◽  
Langevin Model ◽  
Pair Separation ◽  
Decaying Turbulence

We examine results of direct numerical simulations (DNS) of homogeneous turbulence in the presence of stable stratification. We focus on the effects of stratification on eddy diffusion, and the distribution of pairs of particles released in the flow. DNS results are presented over a range of stratification, and at Reynolds numbers compatible with aliased free spectral results for a resolution of 128 mesh points. We compare results for particle dispersion to simple analytic theories such as that proposed by Csanady (1964) and Pearson et al. (1983) by adapting the basic Langevin model to decaying turbulence at low Reynolds numbers. Stable stratification is found to arrest both single particle displacements and pair separation in the direction of stratification, but it leaves these quantities nearly unaltered in the transverse direction. With respect to the dynamics of stratified flows, we find that regions of strong viscous dissipation are intermittently spaced, and are associated with large horizontal vorticity, consistent with recent experimental results by Fincham et al. (1994).

Effect of Improved ThO2 Particle Dispersion in Nickel on High-Temperature Strength

1970 ◽  
Vol 28 ◽  
pp. 444-445
Author(s):  
E. R. Kimmel ◽  
H. L. Anthony ◽  
W. Scheithauer
Keyword(s):  
High Temperature ◽  
Metal Matrix ◽  
Oxide Particle ◽  
Oxide Phase ◽  
Dislocation Motion ◽  
Particle Dispersion ◽  
High Temperature Strength ◽  
Strengthening Effect ◽  
Oxide Particles ◽  
The Stability

The strengthening effect at high temperature produced by a dispersed oxide phase in a metal matrix is seemingly dependent on at least two major contributors: oxide particle size and spatial distribution, and stability of the worked microstructure. These two are strongly interrelated. The stability of the microstructure is produced by polygonization of the worked structure forming low angle cell boundaries which become anchored by the dispersed oxide particles. The effect of the particles on strength is therefore twofold, in that they stabilize the worked microstructure and also hinder dislocation motion during loading.

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