Passive scalar mixing: Analytic study of time scale ratio, variance, and mix rate

2006 ◽  
Vol 18 (7) ◽  
pp. 075101 ◽  
Author(s):  
J. R. Ristorcelli
Keyword(s):  
Time Scale ◽  
Passive Scalar ◽  
Analytic Study ◽  
Scalar Mixing ◽  
Scale Ratio

Effects of Schmidt Number on Turbulent Mass Transfer Around a Rotating Circular Cylinder

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Dong-Hyeog Yoon ◽  
Kyung-Soo Yang ◽  
Klaus Bremhorst
Keyword(s):  
Mass Transfer ◽  
Circular Cylinder ◽  
Diffusion Layer ◽  
Time Scale ◽  
Schmidt Number ◽  
Concentration Field ◽  
Limiting Behavior ◽  
Rotating Circular Cylinder ◽  
Scale Ratio ◽  
Turbulent Mass Transfer

Characteristics of turbulent mass transfer around a rotating circular cylinder have been investigated by Direct Numerical Simulation. The concentration field was computed for three different cases of Schmidt number, Sc = 1, 10 and 100 at ReR* = 336. Our results confirm that the thickness of the Nernst diffusion layer decreases as Sc increases. Wall-limiting behavior within the diffusion layer was examined and compared with that of channel flow. Concentration fluctuation time scale was found to scale with r+2, while the time scale ratio nearly equals the Schmidt number throughout the diffusion layer. Scalar modeling closure constants based on gradient diffusion models were found to vary considerably within the diffusion layer. Results of an octant analysis show the significant role played by the ejection and sweep events just as is found for flat plate, channel, and pipe flow boundary layers. Turbulence budgets revealed a strong Sc dependence of turbulent scalar transport.

High Rayleigh number convection and passive scalar mixing

1996 ◽  
Vol 97 (1-3) ◽  
pp. 286-290 ◽  
Author(s):  
Boris I. Shraiman ◽  
Eric D. Siggia
Keyword(s):  
Rayleigh Number ◽  
Passive Scalar ◽  
Scalar Mixing

Numerical Simulation of Heavy Particle Dispersion—Scale Ratio and Flow Decay Considerations

1994 ◽  
Vol 116 (1) ◽  
pp. 154-163 ◽  
Author(s):  
Lian-Ping Wang ◽  
David E. Stock
Keyword(s):  
Numerical Simulation ◽  
Time Scale ◽  
Dispersion Coefficient ◽  
Fluid Velocity ◽  
Heavy Particle ◽  
Particle Dispersion ◽  
Heavy Particles ◽  
Velocity Scale ◽  
Scale Ratio ◽  
Diffusivity Ratio

Lagrangian statistical quantities related to the dispersion of heavy particles were studied numerically by following particle trajectories in a random flow generated by Fourier modes. An experimental fluid velocity correlation was incorporated into the flow. Numerical simulation was performed with the use of nonlinear drag. The simulation results for glass beads in a nondecaying turbulent air showed a difference between the horizontal dispersion coefficient and vertical dispersion coefficient. This difference was related to the differences of both the velocity scale and the time scale between the two direction. It was shown that for relatively small particle sizes the particle time scale ratio dominates the value of the diffusivity ratio. For large particles, the velocity scale ratio reaches a value of 1/2 and thus fully determines the diffusivity ratio. Qualitative explanation was provided to support the numerical findings. The dispersion data for heavy particles in grid-generated turbulences were successfully predicted by the simulation when flow decay was considered. As a result of the reduction in effective inertia and the increase in effective drift caused by the flow decay, the particle dispersion coefficient in decaying flow decreases with downstream location. The particle rms fluctuation velocity has a slower decay rate than the fluid rms velocity if the drift parameter is large. It was also found that the drift may substantially reduce the particle rms velocity.

scholarly journals Passive Scalar Mixing Downstream of a Synthetic Jet in Crossflow

2008 ◽  
pp. 103-109
Author(s):  
Glen Mitchell ◽  
Emmanuel Benard ◽  
Václav Uruba ◽  
Richard Cooper
Keyword(s):  
Passive Scalar ◽  
Synthetic Jet ◽  
Scalar Mixing ◽  
Jet In Crossflow

Numerical Simulation of Cloud–Clear Air Interfacial Mixing: Homogeneous versus Inhomogeneous Mixing

2009 ◽  
Vol 66 (8) ◽  
pp. 2493-2500 ◽  
Author(s):  
Miroslaw Andrejczuk ◽  
Wojciech W. Grabowski ◽  
Szymon P. Malinowski ◽  
Piotr K. Smolarkiewicz
Keyword(s):  
Time Scale ◽  
Numerical Data ◽  
Droplet Evaporation ◽  
Direct Numerical Simulations ◽  
Heuristic Argument ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Air Mixing ◽  
Scale Ratio ◽  
Bin Microphysics

Abstract This note presents an analysis of several dozens of direct numerical simulations of the cloud–clear air mixing in a setup of decaying moist turbulence with bin microphysics. The goal is to assess the instantaneous relationship between the homogeneity of mixing and the ratio of the time scales of droplet evaporation and turbulent homogenization. Such a relationship is important for developing improved microphysical parameterizations for large-eddy simulation of clouds. The analysis suggests a robust relationship for the range of time scale ratios between 0.5 and 10. Outside this range, the scatter of numerical data is significant, with smaller and larger time scale ratios corresponding to mixing scenarios that approach the extremely inhomogeneous and homogeneous limits, respectively. This is consistent with the heuristic argument relating the homogeneity of mixing to the time scale ratio.

Investigation of passive scalar mixing in a confined rectangular wake using simultaneous PIV and PLIF

2010 ◽  
Vol 65 (11) ◽  
pp. 3372-3383 ◽  
Author(s):  
Hua Feng ◽  
Michael G. Olsen ◽  
James C. Hill ◽  
Rodney O. Fox
Keyword(s):  
Passive Scalar ◽  
Scalar Mixing
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