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Numerical investigation on ultra-high-lift low-pressure turbine cascade aerodynamics at low Reynolds numbers using transition-based turbulence models J. Turbul. (IF 1.573) Pub Date : 2021-01-06 Xiaole Wang; Bing Cui; Zuoli Xiao
ABSTRACT The performance of ultra-high-lift (UHL) low-pressure turbine (LPT) is subject to complex flow phenomena (e.g. separation, transition and reattachment) which require advanced modelling for accurate numerical predictions. The feasibility and fidelity of three widely used transition-based turbulence models are evaluated in the Reynolds-Averaged Navier-Stokes (RANS) prediction of low-Reynolds
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Aero-optical suppression for supersonic turbulent boundary layer J. Turbul. (IF 1.573) Pub Date : 2020-11-24 Xi-wan Sun; Xiao-Liang Yang; Wei Liu
Aero-optical reduction in flat-plate turbulent boundary layer has been widely concerned due to critical application for high-speed target-seeking vehicles. From the perspective of disciplinary intersection between aerodynamic and optical engineering, the turbulence-aberrated optical behaviour, in high-Reynolds-number supersonic freestream, is numerically investigated using the in-house code High-Order
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Experimental investigation of the influence of Reynolds number and buoyancy on the flow development of a plane jet in the transitional regime J. Turbul. (IF 1.573) Pub Date : 2020-12-02 P. R. Suresh; T. Sundararajan; K. Srinivasan; Sarit K. Das
Heated horizontal plane jets find wide applications in engineering appliances such as air curtains and discharge of industrial effluents. In the present study, experimental investigations are conducted on a heated horizontal plane jet with the Reynolds numbers in the transitional regime, using a hotwire anemometer. In the far to very far-field (20 < x/d < 100) centreline velocity decay and jet spread
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Energy exchange in a compressible turbulent mixing layer J. Turbul. (IF 1.573) Pub Date : 2020-11-27 V. B. Zametaev; I. I. Lipatov
Asymptotic methods have been used to study a turbulent flat mixing layer comprising a viscous compressible gas flow descending from the trailing edge of a body and a gas at rest having the same chemical composition but a different temperature. In contrast to the existing methods for analysing turbulent flows using the Reynolds-averaged Navier-Stokes (RANS) equations, with some closure hypotheses, this
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Numerical investigation and triple-parameters correlations development on the dynamic characteristics of a turbulent offset jet J. Turbul. (IF 1.573) Pub Date : 2020-12-29 Meriem Ajmi; Nidhal Hnaien; Saloua Marzouk; Lioua Kolsi; Kaouther Ghachem; Habib Ben Aissia
ABSTRACT The present numerical study aims to numerically investigate the dynamic and turbulent characteristics of a two-dimensional and turbulent offset jet. Three different parameters were investigated: The Reynolds numbers (Re) which was varied from 10000 to 30000, wall inclination angle (α) that was from −20° to +20° and finally the offset ratio (OR) which extends from 3.25–13. Ansys Fluent was
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Local dynamic perturbation effects on the scale interactions in wall turbulence J. Turbul. (IF 1.573) Pub Date : 2020-12-29 Zhanqi Tang; Xingyu Ma; Nan Jiang; Xiaotong Cui; Xiaobo Zheng
An experimental investigation of near-wall scale interactions in the presence of a deterministic forcing input is presented in this work. The external forcing input was generated by a wall-mounted piezoelectric (PZT) actuator, which directly introduces a dynamic perturbation into the near-wall cycle of turbulent boundary layer flow. The spectra of velocity fluctuations indicated that the fundamental
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Assessment of turbulence models for single phase CFD computations of a liquid-liquid hydrocyclone using OpenFOAM J. Turbul. (IF 1.573) Pub Date : 2020-12-29 Rodrigo Petrone dos Anjos; Ricardo de Andrade Medronho; Tnia Suaiden Klein
Hydrocyclones are widely used in industry and CFD has been used to compute them. Reynolds stress turbulence models (RSM), which are computationally costly and oftentimes hard to converge, are often recommended in these computations. The present work has selected a liquid-liquid separation hydrocyclone for which single-phase experimental tangential and axial velocity profiles are available. CFD has
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RANS Model development on temperature variance in conjugate heat transfer J. Turbul. (IF 1.573) Pub Date : 2020-12-22 Gaoqiang Yang; Hector Iacovides; Timothy Craft; David Apsley
In this study, a RANS model of turbulent conjugate heat transfer has been developed, which is applicable across a range of different combination of fluid and solid thermal properties. This is achieved by focusing on the transport equations for the temperature variance and its dissipation rate across the solid walls which bound the flow region. In this investigation we make use of a wider range of DNS
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Hysteresis behaviour in spanwise rotating plane Couette flow at Re w = 2600 J. Turbul. (IF 1.573) Pub Date : 2020-12-09 Yuhan Huang; Zhenhua Xia; Shiyi Chen
Hysteresis behaviour was reported in spanwise rotating plane Couette flow (RPCF) at Reynolds number R e w = U w h / ν = 1300 with varying rotation number R o = 2 Ω z h / U w in a recent work (Huang et al. Phys. Rev. Fluids 2019;4:052401(R)). Here, U w is half of the velocity difference between two walls, h is half of the channel width, ν is the kinematic viscosity and Ω z is the constant angular velocity
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Cyclone–anticyclone asymmetry in rotating thin fluid layers J. Turbul. (IF 1.573) Pub Date : 2020-12-02 G. Boffetta; F. Toselli; M. Manfrin; S. Musacchio
We report of a series of laboratory experiments and numerical simulations of freely decaying rotating turbulent flows confined in domains with variable height. We show that the vertical confinement has important effects on the formation of large-scale columnar vortices, the hallmark of rotating turbulence, and in particular delays the development of the cyclone–anticyclone asymmetry. We compare the
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Direct numerical simulation study on the mechanisms of the magnetic field influencing the turbulence in compressible magnetohydrodynamic flow J. Turbul. (IF 1.573) Pub Date : 2020-11-16 C. H. Xu; Y. H. Fan; S. Z. Wang; Z. X. Gao; C. W. Jiang; C. H. Lee
The magnetohydrodynamic (MHD) control has great potential in the applications of hypersonic vehicles. Typically, the MHD flowfield in these applications is low magnetic Reynolds (Rem ) compressible turbulent flow, which is different from that without magnetic field and within the high Rem range. This paper investigated the low Rem compressible MHD isotropic turbulence in different Taylor-scale Reynolds
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Effects of CFJ flow control on aerodynamic performance of symmetric NACA airfoils J. Turbul. (IF 1.573) Pub Date : 2020-11-18 Abdolamir Bak Khoshnevis; Shima Yazdani; Erfan Salimipour
This paper investigates the effects of co-flow jet on the aerodynamic performance of some symmetric blade sections of wind turbines. The Reynolds number of 1.3 × 105, angles of attack between 0° and 18° and momentum coefficients of 0.03, 0.05, and 0.08 are considered for four airfoils of NACA 0012, 0015, 0018, and 0021 as the blade sections. To numerically simulate the fluid flow, the Navier-Stokes
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A scaling law for the required transition zone depth in hybrid LES-DNS J. Turbul. (IF 1.573) Pub Date : 2020-11-20 C. A. Z. Towery; S. Walters; S. M. Guzik; X. Gao; P. E. Hamlington
There is a substantial need to better understand multi-physics interactions in realistic laboratory experiments, yet it is currently unfeasible to perform direct numerical simulations (DNS) of most such problems. As a result, reduced-order models such as those used to represent unclosed subgrid-scale stresses in large-eddy simulations (LES) and advanced numerical techniques, including adaptive mesh
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Turbulent flow characteristics over forward-facing obstacle J. Turbul. (IF 1.573) Pub Date : 2020-12-02 Debasmita Chatterjee; B. S. Mazumder; Subir Ghosh; K. Debnath
The local flow field and wake region over a forward-facing obstacle were experimentally investigated, when the water surface above the obstacle was dipped compared to flow further upstream and further downstream. The obstacle was modelled resembling the shape of an airfoil with a flat top having stoss-side slope 35 ∘ and downstream lee-side slope 6 ∘ designed for minimal flow separation. The submerged
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Calibration and evaluation of a spatial scaling method for the near-wall turbulent flow of viscoelastic fluids J. Turbul. (IF 1.573) Pub Date : 2020-09-21 Takashi Ohta; Daiki Eguchi; Akihiro Hayashi
We performed direct numerical simulations of a turbulent channel flow in viscoelastic fluids to assess various spatial scaling methods and to find a scaling method that can visualise the spatial features regardless of fluid properties. The Giesekus and Oldroyd-B models were used as constitutive equations to model the viscoelastic fluids alongside a Newtonian fluid. The initial scaling method that can
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Observing production and growth of Tollmien–Schlichting waves in subsonic flat plate boundary layer via exciters-free high fidelity numerical simulation J. Turbul. (IF 1.573) Pub Date : 2020-10-12 A. I. Tolstykh; D. A. Shirobokov
A numerical solution of the Navier–Stokes equations describing the instability of a two-dimensional subsonic flow about a flat plate is presented. It is obtained with the 16th-order multioperators-based scheme without introducing artificial exciters. It shows how small numerical disturbances produced by the scheme generate downstream from the leading edge a succession of wave packets formed by the
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A note on fitting a generalised Moody diagram for wall modelled large-eddy simulations J. Turbul. (IF 1.573) Pub Date : 2020-10-30 Charles Meneveau
ABSTRACT Motivated by the needs of wall modelled Large Eddy Simulation (LES), we introduce fits to numerical solutions of the Reynolds Averaged Navier–Stokes equations in their simplest near-wall, boundary layer approximation including a mixing-length model. We formulate the problem such that independent dimensionless variables are those directly available in LES. We provide practical fits for the
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Editorial J. Turbul. (IF 1.573) Pub Date : 2020-10-30 Federico Toschi
(2020). Editorial. Journal of Turbulence: Vol. 21, The machine learning: Guest edited by Federico Toschi, pp. 483-483.
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Spatio-temporal deep learning models of 3D turbulence with physics informed diagnostics J. Turbul. (IF 1.573) Pub Date : 2020-10-15 Arvind T. Mohan; Dima Tretiak; Misha Chertkov; Daniel Livescu
Direct Numerical Simulations (DNSs) of high Reynolds number turbulent flows, encountered in engineering, earth sciences, and astrophysics, are not tractable because of the curse of dimensionality associated with the number of degrees of freedom required to resolve all the dynamically significant spatio-temporal scales. Designing efficient and accurate Machine Learning (ML)-based reduced models of fluid
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Actuator line method applied to grid turbulence generation for large-Eddy simulations J. Turbul. (IF 1.573) Pub Date : 2020-08-13 F. Houtin-Mongrolle; L. Bricteux; P. Benard; G. Lartigue; V. Moureau; J. Reveillon
The constant growth of computational resources allows performing Large-Eddy Simulation (LES) on realistic flow configurations. In this context, it is important to properly model boundary conditions and particularly inflow turbulence. This study addresses wind tunnel applications where the object under investigation is downstream of a turbulence grid. This grid aims at generating a highly turbulent
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Effects of Reynolds number on flow and mixing characteristics of a self-sustained swinging jet J. Turbul. (IF 1.573) Pub Date : 2020-09-22 Dinku Seyoum Zeleke; Rong Fung Huang; Ching Min Hsu
The effects of Reynolds number on flow and mixing characteristics of a merged single swinging jet induced by a V-shaped fluidic oscillator were studied experimentally. The jet Reynolds number was varied from 80 to 3000. A high-speed digital camera was used to capture the instantaneous flow evolution processes using the laser light-sheet-assisted flow visualisation method. Long-exposure images together
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On the importance of the drag coefficient modelling in the double averaged Navier-Stokes equations for prediction of the roughness effects J. Turbul. (IF 1.573) Pub Date : 2020-09-09 F. Chedevergne; P. Forooghi
The Discrete Element Method (DEM) for modelling of flow over rough walls is revised in the framework of the DANS (Double Averaged Navier-Stokes) equations, with a special focus on the drag term appearing in the mean momentum equation as a key to the robustness of the model. A set of 14 Direct Numerical Simulations (DNS) of channel flows with systematically varying roughness topographies is considered
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Wall-shear stress fluctuations in a supersonic turbulent boundary layer over an expansion corner J. Turbul. (IF 1.573) Pub Date : 2020-07-23 Fulin Tong; Jianqiang Chen; Dong Sun; Xinliang Li
The effect of wall expansion on the structural and statistical characteristics of wall-shear stress (WSS) fluctuations was investigated by direct numerical simulations of a supersonic turbulent boundary layer over a sharp expansion corner with various deflection angles (β = 00, 20, 50 and 100). It is found that the two-dimensional fields of WSS are characterised as streamwise-elongated streaky structures
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Towards a self-consistent Boltzmann's kinetic model of fluid turbulence J. Turbul. (IF 1.573) Pub Date : 2020-07-22 Sauro Succi
A closure for the effective relaxation time of the Boltzmann–BGK kinetic equation for fluid turbulence is presented, based on a double-averaging procedure over both kinetic and turbulent fluctuations. The resulting effective relaxation time appears to agree with values obtained via a renormalisation group treatment of the Navier–Stokes equation only at low values of k/T, the ratio of turbulent kinetic
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Large eddy simulation of the periodic cavity evolution and the turbulence characteristics around a Delft Twist-11 hydrofoil J. Turbul. (IF 1.573) Pub Date : 2020-07-27 An Yu; Xincheng Wang; Qinghong Tang; Daqing Zhou
In the present investigation, the LES WALE method along with the Zwart cavitation model is utilised to predict the cavitating flow around a Delft Twist-11 hydrofoil and the numerical results show a reasonable agreement with the experimental data. A novel elucidation is provided to the formation of the U-type structure and the Lumley method is introduced into the numerical simulation which can offer
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Controlling Rayleigh–Bénard convection via reinforcement learning J. Turbul. (IF 1.573) Pub Date : 2020-07-29 Gerben Beintema; Alessandro Corbetta; Luca Biferale; Federico Toschi
Thermal convection is ubiquitous in nature as well as in many industrial applications. The identification of effective control strategies to, e.g. suppress or enhance the convective heat exchange under fixed external thermal gradients is an outstanding fundamental and technological issue. In this work, we explore a novel approach, based on a state-of-the-art Reinforcement Learning (RL) algorithm, which
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Numerical study of passive forcing on the secondary instability of a laminar planar free shear layer J. Turbul. (IF 1.573) Pub Date : 2020-06-01 H. Valtchanov; J. R. Brinkerhoff; M. I. Yaras
Direct numerical simulations were performed of a free shear layer developing downstream from a no-slip splitter plate. The simulation results show that three-dimensional streaky perturbations developing in the boundary layer on the high-speed side of the splitter plate are convected downstream from the trailing edge and influence the development of three-dimensional perturbations in the planar free
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Transitional and turbulent flows in rectangular ducts: budgets and projection in principal mean strain axes J. Turbul. (IF 1.573) Pub Date : 2020-06-18 Paolo Orlandi; Sergio Pirozzoli
We carry out Direct Numerical Simulation (DNS) of flows in closed rectangular ducts with several aspect ratios. The Navier–Stokes equations are discretised through a second-order finite difference scheme, with non-uniform grids in two directions. The duct cross-sectional area is maintained constant as well as the flow rate, which allows to investigate which is the appropriate length scale in the Reynolds
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Comparison between temporal and spatial direct numerical simulations for bypass transition flows J. Turbul. (IF 1.573) Pub Date : 2020-07-13 Satish Muthu; Shanti Bhushan
Temporally developing direct numerical simulations (T-DNS) are performed for free-stream turbulence induced bypass transition flow over a flat-plate under zero-pressure gradient, and results are validated using experimental data and spatially developing DNS (S-DNS) results. The temporal simulations predict the growth of near-wall Klebanoff modes in the pre-transition regime and their subsequent breakdown
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A perspective on machine learning in turbulent flows J. Turbul. (IF 1.573) Pub Date : 2020-04-24 Sandeep Pandey; Jörg Schumacher; Katepalli R. Sreenivasan
The physical complexity and the large number of degrees of freedom that can be resolved today by direct numerical simulations of turbulent flows, and by the most sophisticated experimental techniques, require new strategies to reduce and analyse the data so generated, and to model the turbulent behaviour. We discuss a few concrete examples for which the turbulence data have been analysed by machine
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Length scales in turbulent free shear flows J. Turbul. (IF 1.573) Pub Date : 2020-04-15 G. Cafiero; M. Obligado; J.C. Vassilicos
We address the important point of the proportionality between the longitudinal integral lengthscale (L) and the characteristic mean flow width (δ) using experimental data of an axisymmetric wake and a turbulent planar jet. This is a fundamental hypothesis when deriving the self-similar scaling laws in free shear flow. We show that L/δ is indeed constant, at least in a range of streamwise distances
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Staircase scaling of short-time energy transfer in turbulence J. Turbul. (IF 1.573) Pub Date : 2020-04-21 L. Fang; T. Wu; Wouter J.T. Bos
It is illustrated that a sharply truncated initial kinetic energy spectrum evolves to a staircase-shaped spectrum at short times. This effect is directly associated with the triadic nature of the energy transfer. A rigorous analysis leads to predictions on the time-dependence of this effect, and these predictions are verified by both direct numerical simulations and eddy-damped quasi-normal Markovian
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Three-dimensional inert and reactive shock-interface interactions: statistical flow characterisations J. Turbul. (IF 1.573) Pub Date : 2020-04-21 Dandan Wang; Gang Dong
Three-dimensional inert and reactive shock-interface interactions are simulated by solving NS equation with ninth-order WENO scheme. An initial planar shock wave with Mach number 1.7 accelerates a single mode and finite thickness interface with initial wavelength 4 mm and amplitude 0.4 mm from the reactant composed of C2H4+3O2+4N2. Then the transmitting shock branch is reflected at the end boundary
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Direct numerical simulations of forced homogeneous isotropic turbulence in a dense gas J. Turbul. (IF 1.573) Pub Date : 2020-03-19 A. Giauque; C. Corre; A. Vadrot
Direct Numerical Simulations (DNS) of forced homogeneous isotropic turbulence in a dense gas (FC-70), accurately described by a complex EoS, are computed for a turbulent Mach number of 0.8. In a numerical experiment, results are compared to the ones obtained when considering the fluid as a perfect gas. It is found that the dense gas displays a deeply modified shocklets' structure. The amplitude of
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Effect of hemispherical turbulators in a double-pipe heat exchanger for heat transfer augmentation J. Turbul. (IF 1.573) Pub Date : 2020-03-19 Shiva Kumar; P. Dinesha; Akshith Narayanan; Rahul Nanda
In a double-pipe heat exchanger, heat transfer enhancement can be carried out by active or passive methods. In the present study, heat transfer characteristics are studied by the addition of hemispherical turbulators placed in the annulus region in a double-pipe heat exchanger. The turbulators are placed in the annulus region on the inner pipe separated at 90° to each other around the circumference
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Experimental investigation of turbulent boundary layers at high Reynolds number with uniform blowing, part I: statistics J. Turbul. (IF 1.573) Pub Date : 2020-03-17 G. Hasanuzzaman; S. Merbold; C. Cuvier; V. Motuz; J.-M. Foucaut; Ch. Egbers
Uniform blowing in wall bounded shear flows is well known for its drag reducing effects and has long been investigated ever since. However, many contemporary and former research on this topic has confirmed the drag reducing effect but very less is known regarding how blowing is effecting the Reynolds stresses at high Reynolds number. Therefore, effect of uniform blowing has been experimentally investigated
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Monte Carlo science J. Turbul. (IF 1.573) Pub Date : 2020-03-19 Javier Jiménez
This paper explores how far the scientific discovery process can be automated. Using the identification of causally significant flow structures in two-dimensional turbulence as an example, it probes how far the usual procedure of planning experiments to test hypotheses can be substituted by ‘blind’ randomised experiments and notes that the increased efficiency of computers is beginning to make such
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Improving LES with OpenFOAM by minimising numerical dissipation and use of explicit algebraic SGS stress model J. Turbul. (IF 1.573) Pub Date : 2019-12-26 Matteo Montecchia, Geert Brethouwer, Stefan Wallin, Arne V. Johansson, Thilo Knacke
There is a rapidly growing interest in using general-purpose CFD codes based on second-order finite volume methods for Large-Eddy Simulation (LES) in a wide range of applications, and in many cases involving wall-bounded flows. However, such codes are strongly affected by numerical dissipation and the accuracy obtained for typical LES resolutions is often poor. In the present study, we approach the
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Turbulence structures over realistic and synthetic wall roughness in open channel flow at Reτ = 1000 J. Turbul. (IF 1.573) Pub Date : 2019-12-25 Mostafa Aghaei Jouybari, Giles J. Brereton, Junlin Yuan
Turbulence structures in flow over three types of wall roughness: sand-grain, cube roughness and a realistic, multi-scale turbine-blade roughness, are compared to structures observed in flow over a smooth wall in open channel flow at Reτ=1000, using direct numerical simulations. Two-point velocity correlations, length scales, inclination angles, and velocity spectra are analysed, and the applicability
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Neural network models for the anisotropic Reynolds stress tensor in turbulent channel flow J. Turbul. (IF 1.573) Pub Date : 2019-12-24 Rui Fang; David Sondak; Pavlos Protopapas; Sauro Succi
Reynolds-averaged Navier-Stokes (RANS) equations are presently one of the most popular models for simulating turbulence. Performing RANS simulation requires additional modelling for the anisotropic Reynolds stress tensor, but traditional Reynolds stress closure models lead to only partially reliable predictions. Recently, data-driven turbulence models for the Reynolds anisotropy tensor involving novel
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Transpired turbulent boundary layers: a general strategy for RANS turbulence models J. Turbul. (IF 1.573) Pub Date : 2019-12-15 François Chedevergne, Yann Marchenay
Transpired boundary layers are of major interest for many industrial applications. Although well described, there is no turbulence model specifically dedicated to the prediction of boundary layers for both blowing and suction configurations. Revisiting closure relations of turbulence models, a general strategy was established to recover Stevenson's law of the wall that described the behaviour of transpired
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On the kinematics of scalar iso-surfaces in decaying homogeneous, isotropic turbulence J. Turbul. (IF 1.573) Pub Date : 2019-11-28 Brandon C. Blakeley, Weirong Wang, James J. Riley
Scalar iso-surfaces have been used to describe many interface problems in turbulence, such as flame surfaces in turbulent reacting flows and turbulent/non-turbulent interfaces. In this paper we report on direct numerical simulations of the behaviour of iso-surfaces of two differently initialised conserved scalars evolving in isotropic turbulence. The terms in the equation for the iso-surface area density
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A generalised wall function including compressibility and pressure-gradient terms for the Spalart–Allmaras turbulence model J. Turbul. (IF 1.573) Pub Date : 2019-11-17 Amit Joshi, Ashwani Assam, M. R. Nived, Vinayak Eswaran
Spalart-Allmaras (SA) model is a low Reynolds number (Re) model, which means that the first off-wall grid point should be placed in the viscous sub-layer with y+≃1. This restriction of placing the first off-wall grid point so close to the wall leads to an increase in the mesh size, and thus the computation. The wall function approach is an alternative to this problem. The standard wall function method
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Numerical prediction of interaction between turbulence structures and vortex cavitation J. Turbul. (IF 1.573) Pub Date : 2019-11-03 Takashi Ohta, Ryutaro Sugiura
A novel numerical method to perform direct numerical simulations (DNS) of turbulent flow was established to predict the characteristics of compressible gas–liquid two-phase flow. A cavitation model was introduced to reproduce the phase change in the cavitation phenomena, and a DNS of wall turbulence of water with cavitation was performed. Vortex cavitation was observed in the wall turbulence. The growing
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On the large- and small-scale motions in a separated, turbulent-boundary-layer flow J. Turbul. (IF 1.573) Pub Date : 2019-10-29 Suranga Dharmarathne, Humberto Bocanegra Evans, Ali M. Hamed, Burak Aksak, Leonardo P. Chamorro, Murat Tutkun, Ali Doosttalab, Luciano Castillo
Adverse-pressure-gradient turbulent boundary layer flow was inspected at Reynolds number based on momentum thickness, Reθ≈1200, using particle image velocimetry in a refractive-index-matching flume. Proper orthogonal decomposition was used to quantify the effect of large-scale motions on the Reynolds stresses at the onset of separation and within the separated flow. Results show that approximately
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The importance of non-normal contributions to velocity gradient tensor dynamics for spatially developing, inhomogeneous, turbulent flows J. Turbul. (IF 1.573) Pub Date : 2019-10-29 P. Beaumard, O. R. H. Buxton, C. J. Keylock
We investigate the properties of the velocity gradient tensor for spatially evolving turbulent flows (a near-wake, two axisymmetric jets and a planar mixing layer). Emphasis is placed on the study of the normal and non-normal parts of the tensor. Non-normality plays a greater role in the dynamics than is observed for HIT and does so for all spatial locations examined. This implies a greater role for
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Turbulence length scales in a low-roughness near-neutral atmospheric surface layer J. Turbul. (IF 1.573) Pub Date : 2019-10-14 Matthew J. Emes, Maziar Arjomandi, Richard M. Kelso, Farzin Ghanadi
This paper investigated the integral length scales of turbulence in a low-roughness atmospheric surface layer (ASL), characterised by very smooth terrain in the Utah desert during near-neutral conditions, and evaluated the Engineering Sciences Data Unit (ESDU) 85020 and 86010 predictions for the turbulence length scales in a low-roughness ASL. The correlation integral method was used to estimate the
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One-dimensional turbulence modelling of incompressible temporally developing turbulent boundary layers with comparison to DNS J. Turbul. (IF 1.573) Pub Date : 2019-10-09 Rakhi, Marten Klein, Juan A. Medina M., Heiko Schmidt
The incompressible temporally developing turbulent boundary layer (TBL) is analysed using the map-based stochastic one-dimensional turbulence (ODT) model. The TBL is a canonical flow problem, which is, in the present study, formed by a planar moving wall and a free stream at rest. An understanding of this idealised flow is of fundamental relevance for the numerical analysis of turbulent boundary-layer-type
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The effect of non-vertical shear on stratified turbulence using the coupling between second-order models J. Turbul. (IF 1.573) Pub Date : 2019-09-17 Lamia Thamri, Taoufik Naffouti, Mounir Bouzaiane
In the present investigation, the evolution of stratified turbulence submitted to a non-vertical shear is studied using second-order models. Different cases of turbulent flows are considered. Firstly, the case of a purely horizontal shear is considered ( θ=π/2). In the second case, we study a purely vertical shear θ=0. Finally, we studied an inclined shear corresponding to θ=π/6,θ=π/4,θ=π/3,π/8,3π/8
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Numerical study of the Richtmyer–Meshkov instability induced by non-planar shock wave in non-uniform flows J. Turbul. (IF 1.573) Pub Date : 2019-09-17 Zhen Wang, Tao Wang, Jingsong Bai, Jiaxin Xiao
The effects of non-uniformity of flows and initial disturbance intensity of the incident shock wave on Richtmyer–Meshkov instability (RMI) when a sinusoidal shock wave with Ma = 1.25 impinging an unperturbed interface are numerically investigated. The interface morphology, turbulent mixing zone width (TMZW), Y-integrated vorticity, circulation, and turbulent kinetic energy (TKE) are qualitatively and
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Influence of the quiescent core on tracer spheroidal particle dynamics in turbulent channel flow J. Turbul. (IF 1.573) Pub Date : 2019-09-16 Yucheng Jie, Chunxiao Xu, James R. Dawson, Helge I. Andersson, Lihao Zhao
Numerical studies into the dynamics of non-spherical particles in turbulent channel flow have, until now, been mostly confined to low Reynolds numbers. In this paper, we investigate the dynamics of tracer non-spherical particles in a channel flow at Reτ≈1000 for the first time. Tracer spheroidal particles suspended in a turbulent channel flow are computed by means of direct numerical simulation coupled
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An efficient numerical method for the generalised Kolmogorov equation J. Turbul. (IF 1.573) Pub Date : 2019-09-11 Davide Gatti, Alberto Remigi, Alessandro Chiarini, Andrea Cimarelli, Maurizio Quadrio
An efficient algorithm for computing the terms appearing in the Generalised Kolmogorov Equation (GKE) written for the indefinite plane channel flow is presented. The algorithm, which features three distinct strategies for parallel computing, is designed such that CPU and memory requirements are kept to a minimum, so that high-Re wall-bounded flows can be afforded. Computational efficiency is mainly
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A Fokker–Planck approach to a moment closure for mixing in variable-density turbulence J. Turbul. (IF 1.573) Pub Date : 2019-09-09 J. R. Ristorcelli, J. Bakosi
We develop a theory for the cascade mixing terms in a moment closure approach to binary active scalar mixing in variable-density turbulence. To address the variable-density complications we apply, as a principle and constraint, the conservation of the probability density function (PDF) through a Fokker–Planck equation with bounded sample space whose attractor is the beta PDF with skewness. Mixing is
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Local equilibrium in the inertial layer of wall bounded turbulence J. Turbul. (IF 1.573) Pub Date : 2019-08-09 Kannan Sundaravadivelu
Recently Brouwers [Dissipation equals production in the log layer of wall-induced turbulence. Phys Fluids. 2007;19:101702] carried out an asymptotic analysis using the RANS based turbulence energy transport equation and showed that the energy dissipation equals its production in the inertial layer of wall-induced turbulence. Assuming log-law profile to the mean velocity, pressure, viscous and energy
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Direct numerical simulations of second-order Stokes wave driven smooth-walled oscillatory channel: investigation of net current formation J. Turbul. (IF 1.573) Pub Date : 2019-08-08 C. E. Ozdemir, X. Yu, S. Sororian, L. Zhu, M. Tyagi, S. Haddadian, D. Oliveira, C. N. Turnipseed, H. Kefelegn
In wall-bounded time-periodic flows, nonlinearity, associated with higher harmonic term(s) in velocity and/or acceleration outside the boundary layer, can significantly change the wall turbulence compared with that in the linear Stokes Boundary Layer. A significant feature of a nonlinear wall-bounded turbulent time-periodic flow is the formation of a net current which has not yet been mechanistically
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A new formulation of fk for the PANS model J. Turbul. (IF 1.573) Pub Date : 2019-07-19 Lars Davidson, Christophe Friess
The partially averaged Navier–Stokes (PANS) model, proposed in Girimaji [Partially-averaged Navier-Stokes model for turbulence: a Reynolds-averaged Navier-Stokes to direct numerical simulation bridging method. ASME J Appl Mech. 2006;73(3):413–421], can be used to simulate turbulent flows either as a RANS, LES or DNS. The PANS model includes fk which denotes the ratio of modelled to total kinetic energy
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Flow structure of the entrance of a T-junction duct without/with a circular cylinder J. Turbul. (IF 1.573) Pub Date : 2019-07-16 Xiaoyu Wang, Jing He, Bo Su, Hanbing Ke, Mei Lin, Yitung Chen
The flow characteristics of the trailing edge of vertical vanes installed at the intersection of a T-junction duct were experimentally investigated using particle image velocimetry. The measured velocity field in the branch duct with/without single circular cylinder was studied under different cross velocities and velocity ratios. Additionally, the effect of the locations of cylinder on the flow field
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Topological evolution near the turbulent/non-turbulent interface in turbulent mixing layer J. Turbul. (IF 1.573) Pub Date : 2019-07-11 Jia-Long Yu, Xi-Yun Lu
The topological evolution near the turbulent/non-turbulent interface (TNTI) in turbulent mixing layer is studied by means of statistical analysis of the invariants of velocity gradient tensor (VGT) based on direct numerical simulation data. The dynamics of topological evolution is investigated in terms of the source terms of the evolution equations for the invariants, including the pressure effect
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Experimental evaluation of the mean momentum and kinetic energy balance equations in turbulent pipe flows at high Reynolds number J. Turbul. (IF 1.573) Pub Date : 2019-06-11 El-Sayed Zanoun, Christoph Egbers, Ramis Örlü, Tommaso Fiorini, Gabriele Bellani, Alessandro Talamelli
In light of recent data from hot-wire anemometry and laser Doppler velocimetry, this article explores experimentally the momentum balance and kinetic energy production in fully developed turbulent pipe flow for shear Reynolds numbers in the range 8⋅102≤R+≤4⋅104 from two pipe facilities. It has become common practice to indirectly deduce the Reynolds shear stress via the mean flow data and the mean-momentum
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Kinetic-magnetic energy exchanges in rotating magnetohydrodynamic turbulence J. Turbul. (IF 1.573) Pub Date : 2019-05-31 F. S. Baklouti, A. Khlifi, A. Salhi, F. Godeferd, C. Cambon, T. Lehner
We use direct numerical simulations to study the dynamics of incompressible homogeneous turbulence subjected to a uniform magnetic field B in a rotating frame with rotation vector Ω. We consider two cases: Ω∥B and Ω⊥B. The initial state is homogeneous isotropic hydrodynamic turbulence with Reynolds number Re=ull/ν≃170. The magnetic Prandtl number Pm=ν/η=1 and the Elsasser number Λ=B2/(2Ωη)=0.5, 0.9
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