Lagrangian views on turbulent mixing of passive scalars

The Lagrangian view of passive scalar turbulence has recently produced interesting results and interpretations. Innovations in theory, experiments, simulations and data analysis of Lagrangian turbulence are reviewed here in brief. Part of the review is closely related to the so-called Kraichnan model for the advection of the passive scalar in synthetic turbulence. Possible implications for a better understanding of the passive scalar mixing in Navier–Stokes turbulence are also discussed.

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Computational Modeling of Turbulent Mixing of a Transverse Jet

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4002015 ◽

2010 ◽

Vol 133 (2) ◽

Cited By ~ 6

Author(s):

Elizaveta M. Ivanova ◽

Berthold E. Noll ◽

Manfred Aigner

Keyword(s):

Turbulent Mixing ◽

Passive Scalar ◽

Navier Stokes ◽

Test Case ◽

Scalar Mixing ◽

Reynolds Stresses ◽

Mixing Processes ◽

Jet In Crossflow ◽

Turbulent Schmidt Number ◽

Reynolds Averaged Navier Stokes

This paper presents numerical simulations of turbulent mixing of a jet in crossflow. The test case is chosen to resemble scalar mixing processes in the premixing zones of gas turbine combustion chambers. Steady and unsteady simulations employing three different computational approaches are presented: steady Reynolds-averaged Navier–Stokes, unsteady Reynolds-averaged Navier–Stokes, and scale-adaptive simulations. Presented results comprise the (time-averaged) profiles of flow velocities, turbulent kinetic energy of the flow, Reynolds stresses, passive scalar distribution, turbulent scalar fluxes, and the turbulent variance of the passive scalar. All presented results are directly validated against experimental data. Additionally, two parameter studies are presented. Both studies are related to the accuracy of the turbulent scalar mixing predictions for all used simulation methods. In the first study, the dependence of the scalar mixing predictions on the value of the turbulent Schmidt number is considered. In the second study, the dependence of the predicted turbulent scalar variance on the used modeling approach is analyzed.

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Computational Modelling of Turbulent Mixing of a Transverse Jet

Volume 2: Combustion, Fuels and Emissions, Parts A and B ◽

10.1115/gt2010-22764 ◽

2010 ◽

Cited By ~ 1

Author(s):

Elizaveta Ivanova ◽

Berthold Noll ◽

Manfred Aigner

Keyword(s):

Turbulent Mixing ◽

Computational Modelling ◽

Passive Scalar ◽

Navier Stokes ◽

Test Case ◽

Scalar Mixing ◽

Reynolds Stresses ◽

Mixing Processes ◽

Turbulent Schmidt Number ◽

Reynolds Averaged Navier Stokes

This paper presents numerical simulations of turbulent mixing of a jet in crossflow. The test case is chosen to resemble scalar mixing processes in the premixing zones of gas turbine combustion chambers. Steady and unsteady simulations employing three different computational approaches are presented: steady Reynolds-Averaged Navier-Stokes (RANS), unsteady Reynolds-Averaged Navier-Stokes (URANS), and Scale-Adaptive Simulations (SAS). Presented results comprise the (time-averaged) profiles of flow velocities, turbulent kinetic energy of the flow, Reynolds stresses, passive scalar distribution, turbulent scalar fluxes, and the turbulent variance of the passive scalar. All presented results are directly validated against experimental data. Additionally two parameter studies are presented. Both studies are related to the accuracy of the turbulent scalar mixing predictions for all used simulation methods. In the first study the dependence of the scalar mixing predictions on the value of the turbulent Schmidt number is considered. In the second study the dependence of the predicted turbulent scalar variance on the used modelling approach is analysed.

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A strategy for large-scale scalar advection in large eddy simulations that use the linear eddy sub-grid mixing model

International Journal of Numerical Methods for Heat &amp Fluid Flow ◽

10.1108/hff-09-2017-0387 ◽

2018 ◽

Vol 28 (10) ◽

pp. 2463-2479 ◽

Cited By ~ 2

Author(s):

Salman Arshad ◽

Bo Kong ◽

Alan Kerstein ◽

Michael Oevermann

Keyword(s):

Turbulent Mixing ◽

Large Scale ◽

Molecular Diffusion ◽

Passive Scalar ◽

Mixing Model ◽

Large Eddy Simulations ◽

High Flux ◽

Scalar Mixing ◽

Content Type ◽

Large Eddy

PurposeThe purpose of this numerical work is to present and test a new approach for large-scale scalar advection (splicing) in large eddy simulations (LES) that use the linear eddy sub-grid mixing model (LEM) called the LES-LEM.Design/methodology/approachThe new splicing strategy is based on an ordered flux of spliced LEM segments. The principle is that low-flux segments have less momentum than high-flux segments and, therefore, are displaced less than high-flux segments. This strategy affects the order of both inflowing and outflowing LEM segments of an LES cell. The new splicing approach is implemented in a pressure-based fluid solver and tested by simulation of passive scalar transport in a co-flowing turbulent rectangular jet, instead of combustion simulation, to perform an isolated investigation of splicing. Comparison of the new splicing with a previous splicing approach is also done.FindingsThe simulation results show that the velocity statistics and passive scalar mixing are correctly predicted using the new splicing approach for the LES-LEM. It is argued that modeling of large-scale advection in the LES-LEM via splicing is reasonable, and the new splicing approach potentially captures the physics better than the old approach. The standard LES sub-grid mixing models do not represent turbulent mixing in a proper way because they do not adequately represent molecular diffusion processes and counter gradient effects. Scalar mixing in turbulent flow consists of two different processes, i.e. turbulent mixing that increases the interface between unmixed species and molecular diffusion. It is crucial to model these two processes individually at their respective time scales. The LEM explicitly includes both of these processes and has been used successfully as a sub-grid scalar mixing model (McMurtry et al., 1992; Sone and Menon, 2003). Here, the turbulent mixing capabilities of the LES-LEM with a modified splicing treatment are examined.Originality/valueThe splicing strategy proposed for the LES-LEM is original and has not been investigated before. Also, it is the first LES-LEM implementation using unstructured grids.

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Material Conservation of Passive Scalar Mixing in Finite Scale Navier Stokes Fluid Turbulence

Coarse Grained Simulation and Turbulent Mixing ◽

10.1017/cbo9781316480243.006 ◽

2016 ◽

pp. 87-104 ◽

Cited By ~ 1

Author(s):

J. Raymond Ristorcelli

Keyword(s):

Passive Scalar ◽

Navier Stokes ◽

Scalar Mixing ◽

Fluid Turbulence ◽

Stokes Fluid ◽

Material Conservation

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The universality of dynamic multiscaling in homogeneous, isotropic Navier–Stokes and passive-scalar turbulence

New Journal of Physics ◽

10.1088/1367-2630/10/3/033003 ◽

2008 ◽

Vol 10 (3) ◽

pp. 033003 ◽

Cited By ~ 19

Author(s):

Samriddhi Sankar Ray ◽

Dhrubaditya Mitra ◽

Rahul Pandit

Keyword(s):

Passive Scalar ◽

Navier Stokes ◽

Scalar Turbulence

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Spectrum of passive scalars of high molecular diffusivity in turbulent mixing

Journal of Fluid Mechanics ◽

10.1017/jfm.2012.632 ◽

2013 ◽

Vol 716 ◽

Cited By ~ 13

Author(s):

P. K. Yeung ◽

K. R. Sreenivasan

Keyword(s):

Reynolds Number ◽

Turbulent Mixing ◽

Kinematic Viscosity ◽

Schmidt Number ◽

Scalar Fields ◽

Passive Scalar ◽

Careful Examination ◽

Passive Scalars ◽

Molecular Diffusivity ◽

Schmidt Numbers

AbstractWe consider the mixing of passive scalars transported in turbulent flow, with a molecular diffusivity that is large compared to the kinematic viscosity of the fluid. This particular case of mixing has not received much attention in experiment or simulation even though the first putative theory, due to Batchelor, Howells & Townsend (J. Fluid Mech., vol. 5, 1959, pp. 134–139), is now more than 50 years old. We study the problem using direct numerical simulation of decaying scalar fields in steadily sustained homogeneous turbulence as the Schmidt number (the ratio of the kinematic viscosity of the fluid to the molecular diffusivity of the scalar) is allowed to vary from $1/ 8$ to $1/ 2048$ for two values of the microscale Reynolds number, ${R}_{\lambda } \approx 140$ and $\approx $240. The simulations show that the passive scalar spectrum assumes a slope of $- 17/ 3$ in a range of scales, as predicted by the theory, when the Schmidt number is small and the Reynolds number is simultaneously large. The observed agreement between theory and simulation in the prefactor in the spectrum is not perfect. We assess the reasons for this discrepancy by a careful examination of the scalar evolution equation in the light of the assumptions of the theory, and conclude that the finite range of scales resolved in simulations is the main reason. Numerical issues specific to the regime of very low Schmidt numbers are also addressed briefly.

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Scalar mixing in a Kelvin-Helmholtz shear layer and implications for Reynolds-averaged Navier-Stokes modeling of mixing layers

Physical Review E ◽

10.1103/physreve.103.053108 ◽

2021 ◽

Vol 103 (5) ◽

Author(s):

Brandon E. Morgan

Keyword(s):

Shear Layer ◽

Mixing Layers ◽

Navier Stokes ◽

Scalar Mixing ◽

Reynolds Averaged Navier Stokes

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A Code for Simulating Heat Transfer in Turbulent Channel Flow

Mathematics ◽

10.3390/math9070756 ◽

2021 ◽

Vol 9 (7) ◽

pp. 756

Author(s):

Federico Lluesma-Rodríguez ◽

Francisco Álcantara-Ávila ◽

María Jezabel Pérez-Quiles ◽

Sergio Hoyas

Keyword(s):

Heat Transfer ◽

Stokes Equations ◽

Three Dimensional ◽

Turbulent Channel Flow ◽

Passive Scalar ◽

Direct Numerical Simulations ◽

Time Dependent ◽

Navier Stokes ◽

Thermal Flow ◽

Navier Stokes Equations

One numerical method was designed to solve the time-dependent, three-dimensional, incompressible Navier–Stokes equations in turbulent thermal channel flows. Its originality lies in the use of several well-known methods to discretize the problem and its parallel nature. Vorticy-Laplacian of velocity formulation has been used, so pressure has been removed from the system. Heat is modeled as a passive scalar. Any other quantity modeled as passive scalar can be very easily studied, including several of them at the same time. These methods have been successfully used for extensive direct numerical simulations of passive thermal flow for several boundary conditions.

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