Characterizing velocity fluctuations in partially resolved turbulence simulations

A new partially averaged Navier-Stokes (PANS) closure is derived based on the KSKL model. The aim of this new model is to incorporate the desirable features of the KSKL model, compared to the SST model, into the PANS framework. These features include reduced eddy-viscosity levels, a lower dependency on the cell height at the wall, well-defined boundary conditions, and improved iterative convergence. As well as the new model derivation, the paper demonstrates that these desirable features are indeed maintained, for a range of modeled-to-total turbulence kinetic energy ratios (f_k), and even for multiphase flow.

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“…In the case of PANS-KSKL, following the relationship derived by Ref. [44], the PANS length scales can be related to the RANS length scales using…”

Section: Ffiffiffiffi Ffi Kl P Equationmentioning

confidence: 99%

The Development of a Partially Averaged Navier–Stokes KSKL Model

Klapwijk

Lloyd

Vaz³

2022

Journal of Fluids Engineering

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“…The flow field of PANS and other SRS methods can be analysed most conveniently as the direct numerical simulation of a non-Newtonian fluid at a lower effective computational Reynolds number Re e (Reyes et al 2014),…”

Section: Partially-averaged Navier-stokes Equationsmentioning

confidence: 99%

“…In order to illustrate this, assume a high Reynolds number flow so that all dissipation occurs entirely in the unresolved scales -f = 1.00. Then, it is possible to estimate the range of scales being resolved for a given f k (Reyes et al 2014),…”

Section: Partially-averaged Navier-stokes Equationsmentioning

confidence: 99%

“…In general, the SRS approach is amenable to the paradigm that such a simulation is equivalent to a DNS of a variable viscosity non-Newtonian fluid (Rivlin 1957;Muschinski 1996;Reyes et al 2014). This permits the consideration of the spatially-developing coherent structures in a SRS computation as the onset and development of instabilities in a non-Newtonian fluid.…”

Section: Introductionmentioning

confidence: 99%

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Challenges in Modelling and Simulation of Turbulent Flows with Spatially-Developing Coherent Structures

Pereira,

Eca,

Vaz

et al. 2018

Preprint

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The objective of this work is to investigate the fundamental challenges encountered in modelling and simulation of turbulent flows driven by spatially-developing coherent structures. Scale-Resolving Simulations (SRS's) of practical interest are expressly intended for efficiently computing such flows by resolving only the most important features of the coherent structures and modelling the remainder as stochastic field. With reference to a typical Large-Eddy Simulation (LES), practical SRS methods seek to resolve a considerably narrower range of scales (physical resolution) to achieve an adequate degree of accuracy at reasonable computational effort. The success of SRS methods depends upon three important factors: i) ability to identify key flow mechanisms responsible for the generation of coherent structures; ii) determine the optimum range of resolution required to adequately capture key elements of coherent structures; and iii) ensure that the modelled part is comprised nearly exclusively of fully-developed stochastic turbulence. This study considers the canonical case of the flow around a circular cylinder to address the aforementioned three key issues. It is first demonstrated using experimental evidence that the vortex-shedding instability and flow-structure development involves four important stages. The inherent limitations of the Reynolds-Averaged Navier-Stokes (RANS) approach in addressing the flow physics in these four stages of development are explained. A series of SRS computations of progressively increasing resolution (decreasing cut-off length) are performed. An a priori basis for locating the origin of the coherent structures development is proposed and examined. The criterion is based on the fact that the coherent structures are generated by the Kelvin-Helmholtz (KH) instability. The most important finding is that the key aspects of coherent structures can be resolved only if the effective computational Reynolds number (based on total viscosity) exceeds the critical value of the KH instability in laminar flows. Finally, a quantitative criterion assessing the nature of the unresolved field based on the strain-rate ratio of mean and unresolved fields is examined. Based on the findings, quantitative guidelines for determining the optimal degree of physical resolution in flows of practical interest are proposed.

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“…The scientists used various formulations to simulate the phenomena. Girimaji used a Pressure-Strain correlation [56,57], Reynolds Stress Closure Equations [58], and Partially-Averaged Navier-Stokes Model [59][60][61]. It is known that the Surface-Roughness can affect the mean flow past circular cylinder [46,62].…”

Section: Introductionmentioning

confidence: 99%

Optimal Design of Circular Baffles on Sloshing in a Rectangular Tank Horizontally Coupled by Structure

Jamalabadi

Ho-Huu

Nguyen

2018

Water

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Parametric studies on the optimization of baffles on vibration suppression of partially filled tanks coupled by structure have been widely conducted in literature. However, few studies focus on the effect of the position of the baffles on fluid flow stratification and dampening the motion. In the present study, a numerical investigation, an engineering analysis, and optimal design study were performed to determine the effect of external flow on circular obstacle baffles performance on suppressing the vibrations of coupled structure in a closed basin. The single degree of freedom model (mass–spring–damper) is used to model the structure that holds the tank. The coupled system is released from an initial displacement without a velocity. The governing mass, turbulent Navier–Stokes momentum, volume of fluid, and one degree of freedom structure equations are solved by the Pressure-Implicit with Splitting of Operators algorithm in fluids and Newmark method in structure. Based on a detailed study of transient structure motion coupled with sloshing dynamics, the optimal baffle location was achieved. Optimal position of the baffle and its width are systematically obtained with reference to the quiescent free surface.

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Characterizing velocity fluctuations in partially resolved turbulence simulations

Cited by 16 publications

References 32 publications

The Development of a Partially Averaged Navier–Stokes KSKL Model

The Development of a Partially Averaged Navier–Stokes KSKL Model

Challenges in Modelling and Simulation of Turbulent Flows with Spatially-Developing Coherent Structures

Optimal Design of Circular Baffles on Sloshing in a Rectangular Tank Horizontally Coupled by Structure

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