Subgrid turbulence mixing

2021 ◽  
pp. 205-227
Author(s):  
Xu Zhang
Keyword(s):  
Turbulence Mixing

TURBULENCE & MIXING | Turbulent Diffusion

2015 ◽  
pp. 277-286 ◽  
Author(s):  
A. Venkatram ◽  
S. Du
Keyword(s):  
Turbulent Diffusion ◽  
Turbulence Mixing

scholarly journals Entropy Generation Rates in Two-Dimensional Rayleigh–Taylor Turbulence Mixing

Entropy ◽  
2018 ◽  
Vol 20 (10) ◽  
pp. 738 ◽  
Author(s):  
Xinyu Yang ◽  
Haijiang He ◽  
Jun Xu ◽  
Yikun Wei ◽  
Hua Zhang
Keyword(s):  
Time Evolution ◽  
Entropy Generation ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Two Dimensional ◽  
Spatial Averaging ◽  
Mixing Process ◽  
Thermal Entropy ◽  
Large Gradient ◽  
Turbulence Mixing

Entropy generation rates in two-dimensional Rayleigh–Taylor (RT) turbulence mixing are investigated by numerical calculation. We mainly focus on the behavior of thermal entropy generation and viscous entropy generation of global quantities with time evolution in Rayleigh–Taylor turbulence mixing. Our results mainly indicate that, with time evolution, the intense viscous entropy generation rate s u and the intense thermal entropy generation rate S θ occur in the large gradient of velocity and interfaces between hot and cold fluids in the RT mixing process. Furthermore, it is also noted that the mixed changing gradient of two quantities from the center of the region to both sides decrease as time evolves, and that the viscous entropy generation rate ⟨ S u ⟩ V and thermal entropy generation rate ⟨ S θ ⟩ V constantly increase with time evolution; the thermal entropy generation rate ⟨ S θ ⟩ V with time evolution always dominates in the entropy generation of the RT mixing region. It is further found that a “smooth” function ⟨ S u ⟩ V ∼ t 1 / 2 and a linear function ⟨ S θ ⟩ V ∼ t are achieved in the spatial averaging entropy generation of RT mixing process, respectively.

Autonomous Ocean Turbulence Measurements From a Moored Upwardly Rising Profiler Based on a Buoyancy-Driven Mechanism

2017 ◽  
Vol 51 (4) ◽  
pp. 12-22 ◽  
Author(s):  
Xiuyan Liu ◽  
Xin Luan ◽  
Z. Daniel Deng ◽  
Dalei Song ◽  
Shengbo Zang ◽  
...  
Keyword(s):  
The Novel ◽  
Ocean Turbulence ◽  
Turbulence Measurements ◽  
Sea Trial ◽  
Dissipation Rates ◽  
Turbulence Mixing ◽  
Mooring Cable ◽  
High Vertical Resolution ◽  
New Perspective

AbstractAn autonomous Moored Reciprocating Vertical Profiler (MRVP) has been developed and tested for measuring ocean turbulence. The MRVP is designed to combine the advantages of long-term moored measurements at specified depths with those of short-term ship-supported continuous profiling performed at high vertical resolution. The profiler is programmed to repeat vertical motions autonomously along the mooring cable based on a buoyancy-driven mechanism. A sea trial has been conducted in the South China Sea to evaluate the performance of the profiler. The shear probe data are unreliable when the flow past sensors is not sufficiently greater than an estimate of turbulent velocity. For 65% of the dataset, turbulence measurements are of high quality and the magnitude of dissipation rates is up to O(10−10) W kg−1. To minimize the contamination induced by instrument vibration and improve the estimation of turbulent kinetic energy terms, an advanced cross-spectrum algorithm is implemented to the measured shear data. The corrected spectra agreed well with the empirical Nasmyth spectrum, and dissipation rates had averagely decreased a factor of 2 and 8 times lower than the raw spectra. The autonomous MRVP is proven to be a stable platform, and the novel upward measurement provides a new perspective for measuring long-term time series of turbulence mixing.

scholarly journals An Improved Logistic Model Illustrating Microcystis aeruginosa Growth Under Different Turbulent Mixing Conditions

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 669
Author(s):  
Haiping Zhang ◽  
Fan Huang ◽  
Feipeng Li ◽  
Zhujun Gu ◽  
Ruihong Chen ◽  
...  
Keyword(s):  
Microcystis Aeruginosa ◽  
Growth Model ◽  
Turbulent Mixing ◽  
Logistic Model ◽  
Logistic Equation ◽  
Logistic Growth ◽  
Turbulence Mixing ◽  
Population Dynamics Models ◽  
Dynamics Models ◽  
Relationship Of

To overcome the limitations of the normal logistic equation, we aimed to improve the logistic model under hydrodynamic conditions for the examination of the responses of cyanobacterium, coupled turbulence mixing, and growth of cyanobacterium in population dynamics models. Selecting Microcystis aeruginosa and experimenting with the ideal conditions in a laboratory beaker, the chlorophyll-a concentration reached the corresponding maximum under each turbulent condition compared with the control. According to the experiment results, the theory of mass transfer, turbulence mixing, and the logistic equation are organically combined. The improved logistic growth model of Microcystis aeruginosa and competition growth model in the symbiont Scenedesmus quadricauda under turbulent conditions were established. Using the MATLAB multi-parameter surface fitting device, both models produced good fitting effects, with R > 0.95, proving that the results fit the models, and demonstrating the relationship of the unity of nutrient transfer and algae growth affected by turbulence mixing. With continuous increases in turbulent mixing, the fitted curve became smoother and steadier. Algae stimulated by turbulence accelerate reproduction and fission to achieve population dominance. The improved logistic model quantitatively explains the Microcystis aeruginosa response to turbulence and provides a basis to represent ecological and biogeochemical processes in enclosed eutrophic water bodies.

Numerical Investigations of a Turbulence Mixing Process Related to Thermal Striping Phenomena at a T-Junction of Liquid Metal Fast Reactor Piping Systems

2002 ◽  
Author(s):  
Toshiharu Muramatsu
Keyword(s):  
Liquid Metal ◽  
Fast Reactor ◽  
Evaluation System ◽  
Velocity Ratio ◽  
Piping System ◽  
Mixing Process ◽  
Downstream Region ◽  
Piping Systems ◽  
Turbulence Mixing ◽  
Thermal Striping

Fluid-structure thermal interaction phenomena characterized by stationary random temperature fluctuations, namely thermal striping are observed in the downstream region of a T-junction piping system of liquid metal fast reactor (LMFR). Therefore the piping walls located in the downstream region must be protected against the stationary random thermal process which might induced high-cycle fatigue. This paper describes the evaluation system based on numerical simulation methods for the thermal striping, and numerical results of the thermal striping at a T-junction piping system under the various parameters, i.e., velocity ratio and diameter ratio between both the pipes and Reynolds number. Then detailed turbulence mixing process at the T-junction piping region due to arched vortexes generating lower frequency fluctuations are evaluated through a separate numerical analysis of a fundamental water experiment.

scholarly journals Turbulent mixing and beyond: non-equilibrium processes from atomistic to astrophysical scales I

2013 ◽  
Vol 371 (1982) ◽  
pp. 20120436 ◽  
Author(s):  
S. I. Abarzhi ◽  
S. Gauthier ◽  
K. R. Sreenivasan
Keyword(s):  
Present State ◽  
Turbulent Mixing ◽  
Specific Problem ◽  
Equilibrium Dynamics ◽  
Equilibrium Processes ◽  
Turbulence Mixing ◽  
Broad Variety ◽  
The Subject ◽  
Non Equilibrium

In this Introduction, we summarize and provide a perspective on 11 articles on ‘Turbulent mixing and beyond’. The papers represent the broad variety of themes of the subject, and are concerned with fundamental aspects of turbulence, mixing and non-equilibrium dynamics. While each paper deals with a specific problem, the collection gives a panoramic overview of the subject at its present state of understanding.

Large-eddy simulation of the Richtmyer–Meshkov instability

2015 ◽  
Vol 93 (10) ◽  
pp. 1124-1130 ◽  
Author(s):  
T. Wang ◽  
P. Li ◽  
J.S. Bai ◽  
G. Tao ◽  
B. Wang ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Turbulent Kinetic Energy ◽  
Interface Instability ◽  
Simulation Code ◽  
Interface Evolution ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Turbulence Mixing

The subgrid-scale (SGS) terms of turbulence transport are modelled by the stretched-vortex SGS stress model, and a large-eddy simulation code multi-viscous fluid and turbulence (MVFT) is developed to investigate the MVFT problems. Then one AWE shock tube experiment of interface instability is simulated numerically by MVFT code, which reproduces the development process of the interface. The obtained numerical images of interface evolution and wave structures in flow field are consistent with the experimental results. The evolution of perturbed interface and propagation of shock waves in flow field and their interactions are analyzed in detail. The statistics features of turbulence mixing in the form of finer quantities, such as the turbulent kinetic energy, enstrophy, density variance, and turbulent mass flux are investigated, which also proves that the SGS model has a key role in large-eddy simulation. The turbulent kinetic energy and enstrophy decay with time as a power law.

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