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Artículos de revistas sobre el tema "Pr-Dns"

Autor: Grafiati
Publicado: 1 de febrero de 2025
Última modificación: 31 de julio de 2025

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1

Tenneti, Sudheer, Mohammad Mehrabadi, and Shankar Subramaniam. "Stochastic Lagrangian model for hydrodynamic acceleration of inertial particles in gas–solid suspensions." Journal of Fluid Mechanics 788 (January 12, 2016): 695–729. http://dx.doi.org/10.1017/jfm.2015.693.

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The acceleration of an inertial particle in a gas–solid flow arises from the particle’s interaction with the gas and from interparticle interactions such as collisions. Analytical treatments to derive a particle acceleration model are difficult outside the Stokes flow regime, but for moderate Reynolds numbers (based on the mean slip velocity between gas and particles) particle-resolved direct numerical simulation (PR-DNS) is a viable tool for model development. In this study, PR-DNS of freely-evolving gas–solid suspensions are performed using the particle-resolved uncontaminated-fluid reconcil
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2

KERR, ROBERT M., and JACKSON R. HERRING. "Prandtl number dependence of Nusselt number in direct numerical simulations." Journal of Fluid Mechanics 419 (September 25, 2000): 325–44. http://dx.doi.org/10.1017/s0022112000001464.

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The dependence of the Nusselt number Nu on the Rayleigh Ra and Prandtl Pr number is determined for 104 < Ra < 107 and 0.07 < Pr < 7 using DNS with no-slip upper and lower boundaries and free-slip sidewalls in a 8 × 8 × 2 box. Nusselt numbers, velocity scales and boundary layer thicknesses are calculated. For Nu there are good comparisons with experimental data and scaling laws for all the cases, including Ra2/7 laws at Pr = 0.7 and Pr = 7 and at low Pr, a Ra1/4 regime. Calculations at Pr = 0.3 predict a new Nu ∼ Ra2/7 regime at slightly higher Ra than the Pr = 0.07 calculations rep
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3

Song, Jiajun, Panxin Li, Lu Chen, Yuhang Zhao, Fengshi Tian, and Benwen Li. "Scaling Law of Flow and Heat Transfer Characteristics in Turbulent Radiative Rayleigh-Bénard Convection of Optically Thick Media." Energies 17, no. 19 (2024): 5009. http://dx.doi.org/10.3390/en17195009.

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Radiative natural convection is of vital importance in the process of energy storage, power generation, and thermal storage technology. As the attenuation coefficients of many heat transfer media in these fields are high enough to be considered as optically thick media, like nanofluids or molten salts in concentrated solar power or phase change thermal storage, Rosseland approximation is commonly used. In this paper, we delve into the impact of thermal radiation on the Rayleigh-Bénard (RB) convection. Theoretical analysis has been conducted by modifying the Grossmann-Lohse (GL) model. Based on
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4

Fu, Jianhong, Sheng Chen, and Xiaochen Zhou. "Effect of heterogeneity on interphase heat transfer for gas–solid flow: A particle-resolved direct numerical simulation." Physics of Fluids 34, no. 12 (2022): 123317. http://dx.doi.org/10.1063/5.0130850.

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Particle-resolved direct numerical simulation (PR-DNS) of flow past a particle cluster is conducted to analyze the influence of heterogeneous particle distribution on the gas–solid heat transfer calculation. Then, the heat transfer rates calculated using Gunn's correlation are systematically compared with the DNS results for virtual computational fluid dynamics-discrete element method (CFD-DEM) grids with different levels of heterogeneity. The results show that, for a grid located at the interface between the dense cluster region and dilute region, Gunn's correlation significantly overestimate
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5

Cui, Haihang, Qi Chang, Jianhua Chen, and Wei Ge. "PR-DNS verification of the stability condition in the EMMS model." Chemical Engineering Journal 401 (December 2020): 125999. http://dx.doi.org/10.1016/j.cej.2020.125999.

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6

Luo, Heng, Fengbin Zhang, Haibo Huang, et al. "The Effect of Ellipsoidal Particle Surface Roughness on Drag and Heat Transfer Coefficients Using Particle-Resolved Direct Numerical Simulation." Processes 12, no. 11 (2024): 2473. http://dx.doi.org/10.3390/pr12112473.

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The purpose of this study is to estimate the effect of roughness layer thickness on the heat transfer and drag coefficients of ellipsoidal particles. Using an OpenFOAM-based particle-resolved direct numerical simulation (PR-DNS) method, we calculated the drag coefficient and Nusselt number for an isolated axisymmetric nonspherical particle with a rough surface in a uniform flow. The PR-DNS results indicate that the drag coefficient varies linearly with the effective roughness Sef at different angles, which can be expressed as CD=kSef−1+CD0. The changes in k are consistent with the Happel and B
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7

Chilamkurti, Yesaswi N., and Richard D. Gould. "CFD-DEM and PR-DNS studies of low-temperature densely packed beds." International Journal of Heat and Mass Transfer 159 (October 2020): 120056. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2020.120056.

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8

Wu, X., and P. A. Durbin. "Numerical Simulation of Heat Transfer in a Transitional Boundary Layer With Passing Wakes." Journal of Heat Transfer 122, no. 2 (1999): 248–57. http://dx.doi.org/10.1115/1.521485.

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Direct numerical simulation (DNS) has been used to investigate heat transfer and provide thermal statistics in a transitional flow in which turbulent wakes traversing the inlet periodically are swept downstream across a constant-temperature flat-plate. The same heat transfer problem was also computed using unsteady Reynolds-averaged Navier-Stokes (RANS) method with the v2-f turbulence model. During transition, the instantaneous Stanton number field exhibits spotlike structure, which in turn results in a strong streamwise modulation in the phase-averaged Stanton number distribution. At molecula
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9

Trane, D., M. Grespan, and D. Angeli. "Comparison between DNS and RANS approaches for liquid metal flows around a square rod bundle." Journal of Physics: Conference Series 2766, no. 1 (2024): 012009. http://dx.doi.org/10.1088/1742-6596/2766/1/012009.

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Abstract The thermal-hydraulic characteristics of liquid metal flows around rod bundles are of great interest for the research and design of fourth generation nuclear reactors. Currently, a large research effort is aimed at the development of accurate numerical models for low Prandtl number fluid flows, since the data available in the literature are quite scarce. Direct Numerical Simulation (DNS) is undoubtedly the most accurate approach, but its large requirements of computational resources and time make it less practical than other simplified methods such as the Reynolds-Average Navier Stoke
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10

Avsarkisov, V., M. Oberlack, and S. Hoyas. "New scaling laws for turbulent Poiseuille flow with wall transpiration." Journal of Fluid Mechanics 746 (March 28, 2014): 99–122. http://dx.doi.org/10.1017/jfm.2014.98.

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AbstractA fully developed, turbulent Poiseuille flow with wall transpiration, i.e. uniform blowing and suction on the lower and upper walls correspondingly, is investigated by both direct numerical simulation (DNS) of the three-dimensional, incompressible Navier–Stokes equations and Lie symmetry analysis. The latter is used to find symmetry transformations and in turn to derive invariant solutions of the set of two- and multi-point correlation equations. We show that the transpiration velocity is a symmetry breaking which implies a logarithmic scaling law in the core of the channel. DNS valida
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11

Lakehal, D., M. Fulgosi, G. Yadigaroglu, and S. Banerjee. "Direct Numerical Simulation of Turbulent Heat Transfer Across a Mobile, Sheared Gas-Liquid Interface." Journal of Heat Transfer 125, no. 6 (2003): 1129–39. http://dx.doi.org/10.1115/1.1621891.

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The impact of interfacial dynamics on turbulent heat transfer at a deformable, sheared gas-liquid interface is studied using Direct Numerical Simulation (DNS). The flow system comprises a gas and a liquid phase flowing in opposite directions. The governing equations for the two fluids are alternately solved in separate domains and then coupled at the interface by imposing continuity of velocity and stress. The deformations of the interface fall in the range of capillary waves of waveslope ak=0.01 (wave amplitude a times wavenumber k), and very small phase speed-to-friction velocity ratio, c/u*
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12

SHISHKINA, OLGA, and ANDRÉ THESS. "Mean temperature profiles in turbulent Rayleigh–Bénard convection of water." Journal of Fluid Mechanics 633 (August 25, 2009): 449–60. http://dx.doi.org/10.1017/s0022112009990528.

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We report an investigation of temperature profiles in turbulent Rayleigh–Bénard convection of water based on direct numerical simulations (DNS) for a cylindrical cell with unit aspect ratio for the same Prandtl number Pr and similar Rayleigh numbers Ra as used in recent high-precision measurements by Funfschilling et al. (J. Fluid Mech., vol. 536, 2005, p. 145). The Nusselt numbers Nu computed for Pr = 4.38 and Ra = 108, 3 × 108, 5 × 108, 8 × 108 and 109 are found to be in excellent agreement with the experimental data corrected for finite thermal conductivity of the walls. Based on this succe
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13

Wang, Dong, Tai Jin, Kun Luo, Junhua Tan, and Jianren Fan. "Analysis of the particles-induced turbulence in confined gas-solid fluidized beds by PR-DNS." International Journal of Multiphase Flow 141 (August 2021): 103655. http://dx.doi.org/10.1016/j.ijmultiphaseflow.2021.103655.

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14

Chadil, Mohamed-Amine, Stéphane Vincent, and Jean-Luc Estivalèzes. "Gas-Solid Heat Transfer Computation from Particle-Resolved Direct Numerical Simulations." Fluids 7, no. 1 (2021): 15. http://dx.doi.org/10.3390/fluids7010015.

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Particle-Resolved simulations (PR-DNS) have been conducted using a second order implicit Viscous Penalty Method (VPM) to study the heat transfer between a set of particles and an incompressible carrier fluid. A Lagrange extrapolation coupled to a Taylor interpolation of a high order is utilized to the accurate estimate of heat transfer coefficients on an isolated sphere, a fixed Faced-Centered Cubic array of spheres, and a random pack of spheres. The simulated heat transfer coefficients are compared with success to various existing Nusselt laws of the literature.
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15

Kravets, B., D. Schulz, R. Jasevičius, S. R. Reinecke, T. Rosemann, and H. Kruggel-Emden. "Comparison of particle-resolved DNS (PR-DNS) and non-resolved DEM/CFD simulations of flow through homogenous ensembles of fixed spherical and non‐spherical particles." Advanced Powder Technology 32, no. 4 (2021): 1170–95. http://dx.doi.org/10.1016/j.apt.2021.02.016.

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16

Mannix, P. M., and A. J. Mestel. "Weakly nonlinear mode interactions in spherical Rayleigh–Bénard convection." Journal of Fluid Mechanics 874 (July 9, 2019): 359–90. http://dx.doi.org/10.1017/jfm.2019.440.

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In an annular spherical domain with separation $d$, the onset of convective motion occurs at a critical Rayleigh number $Ra=Ra_{c}$. Solving the axisymmetric linear stability problem shows that degenerate points $(d=d_{c},Ra_{c})$ exist where two modes simultaneously become unstable. Considering the weakly nonlinear evolution of these two modes, it is found that spatial resonances play a crucial role in determining the preferred convection pattern for neighbouring modes $(\ell ,\ell \pm 1)$ and non-neighbouring even modes $(\ell ,\ell \pm 2)$. Deriving coupled amplitude equations relevant to a
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17

Mehrabadi, M., J. A. K. Horwitz, S. Subramaniam, and A. Mani. "A direct comparison of particle-resolved and point-particle methods in decaying turbulence." Journal of Fluid Mechanics 850 (July 4, 2018): 336–69. http://dx.doi.org/10.1017/jfm.2018.442.

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We use particle-resolved direct numerical simulation (PR-DNS) as a model-free physics-based numerical approach to validate particle acceleration modelling in gas-solid suspensions. To isolate the effect of the particle acceleration model, we focus on point-particle direct numerical simulation (PP-DNS) of a collision-free dilute suspension with solid-phase volume fraction $\unicode[STIX]{x1D719}=0.001$ in a decaying isotropic turbulent particle-laden flow. The particle diameter $d_{p}$ in the suspension is chosen to be the same as the initial Kolmogorov length scale $\unicode[STIX]{x1D702}_{0}$
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18

Panagiotou, Constantinos F., Fotos S. Stylianou, Elias Gravanis, Evangelos Akylas, and Constantine Michailides. "An Explicit Algebraic Closure for Passive Scalar-Flux: Applications in Channel Flows at a Wide Range of Reynolds Numbers." Journal of Marine Science and Engineering 8, no. 11 (2020): 916. http://dx.doi.org/10.3390/jmse8110916.

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In this paper, we propose an algebraic model for turbulent scalar-flux vector that stems from tensor representation theory. The resulting closure contains direct dependence on mean velocity gradients and quadratic products of the Reynolds stress tensor. Model coefficients are determined from Direct Numerical Simulations (DNS) data of homogeneous shear flows subjected to arbitrary mean scalar gradient orientations, while a correction function was applied at one model coefficient based on a turbulent channel flow case. Model performance is evaluated in Poiseuille and Couette flows at several Rey
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19

Zhang, Hao, Bo Xiong, Xizhong An, Chunhai Ke, and Guangchao Wei. "Prediction on drag force and heat transfer of spheroids in supercritical water: A PR-DNS study." Powder Technology 342 (January 2019): 99–107. http://dx.doi.org/10.1016/j.powtec.2018.09.051.

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20

Zhang, Hao, Lixing Zhang, Xizhong An, and Aibing Yu. "PR-DNS on the momentum and heat transfer of a rotating ellipsoidal particle in a fluid." Powder Technology 373 (August 2020): 152–63. http://dx.doi.org/10.1016/j.powtec.2020.06.030.

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21

Garai, Anirban, Jan Kleissl, and Sutanu Sarkar. "Flow and heat transfer in convectively unstable turbulent channel flow with solid-wall heat conduction." Journal of Fluid Mechanics 757 (September 19, 2014): 57–81. http://dx.doi.org/10.1017/jfm.2014.479.

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AbstractMost turbulent coherent structures in a convectively unstable atmospheric boundary layer are caused by or manifested in ascending warm fluid and descending cold fluids. These structures not only cause ramps in the air temperature timeseries, but also imprint on the underlying solid surface as surface temperature fluctuations. The coupled flow and heat transport mechanism was examined through direct numerical simulation (DNS) of a channel flow allowing for realistic solid–fluid thermal coupling. The thermal activity ratio (TAR; the ratio of thermal inertias of fluid and solid), and the
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22

Shishkina, Olga, Susanne Horn, and Sebastian Wagner. "Falkner–Skan boundary layer approximation in Rayleigh–Bénard convection." Journal of Fluid Mechanics 730 (August 1, 2013): 442–63. http://dx.doi.org/10.1017/jfm.2013.347.

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AbstractTo approximate the velocity and temperature within the boundary layers in turbulent thermal convection at moderate Rayleigh numbers, we consider the Falkner–Skan ansatz, which is a generalization of the Prandtl–Blasius one to a non-zero-pressure-gradient case. This ansatz takes into account the influence of the angle of attack $\beta $ of the large-scale circulation of a fluid inside a convection cell against the heated/cooled horizontal plate. With respect to turbulent Rayleigh–Bénard convection, we derive several theoretical estimates, among them the limiting cases of the temperature
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23

Miao, Haishan, Hao Zhang, Yuhang Wu, Yang Wang, and Xizhong An. "PR-DNS investigation on momentum and heat transfer of two interactive non-spherical particles in a fluid." Powder Technology 427 (September 2023): 118791. http://dx.doi.org/10.1016/j.powtec.2023.118791.

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24

Kolla, H., E. R. Hawkes, A. R. Kerstein, N. Swaminathan, and J. H. Chen. "On velocity and reactive scalar spectra in turbulent premixed flames." Journal of Fluid Mechanics 754 (August 7, 2014): 456–87. http://dx.doi.org/10.1017/jfm.2014.392.

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AbstractKinetic energy and reactive scalar spectra in turbulent premixed flames are studied from compressible three-dimensional direct numerical simulations (DNS) of a temporally evolving rectangular slot-jet premixed flame, a statistically one-dimensional configuration. The flames correspond to a lean premixed hydrogen–air mixture at an equivalence ratio of 0.7, preheated to 700 K and at 1 atm, and three DNS are considered with a fixed jet Reynolds number of 10 000 and a jet Damköhler number varying between 0.13 and 0.54. For the study of spectra, motivated by the need to account for density
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25

STEVENS, RICHARD J. A. M., ROBERTO VERZICCO, and DETLEF LOHSE. "Radial boundary layer structure and Nusselt number in Rayleigh–Bénard convection." Journal of Fluid Mechanics 643 (January 15, 2010): 495–507. http://dx.doi.org/10.1017/s0022112009992461.

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Results from direct numerical simulation (DNS) for three-dimensional Rayleigh–Bénard convection in a cylindrical cell of aspect ratio 1/2 and Prandtl number Pr=0.7 are presented. They span five decades of Rayleigh number Ra from 2 × 106 to 2 × 1011. The results are in good agreement with the experimental data of Niemela et al. (Nature, vol. 404, 2000, p. 837). Previous DNS results from Amati et al. (Phys. Fluids, vol. 17, 2005, paper no. 121701) showed a heat transfer that was up to 30% higher than the experimental values. The simulations presented in this paper are performed with a much highe
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26

Peeters, J. W. R. "Modelling turbulent heat transfer in rough channels using phenomenological theory." Journal of Physics: Conference Series 2116, no. 1 (2021): 012025. http://dx.doi.org/10.1088/1742-6596/2116/1/012025.

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Abstract Rough walls are often encountered in industrial heat transfer equipment. Even though it is well known that a rough wall affects velocity fields and thermal fields differently (and therefore also skin friction factors and Stanton or Nusselt numbers), predicting the effect of rough walls on turbulent heat transfer remains difficult. A relation between the scalar spectrum and the Stanton number is derived for channels with both smooth and rough walls. It is shown that the new relation agrees reasonably well with recent DNS experiments for wall roughness sizes of k + < 150 and when Pr
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27

Wan, Zhen-Hua, Ping Wei, Roberto Verzicco, Detlef Lohse, Guenter Ahlers, and Richard J. A. M. Stevens. "Effect of sidewall on heat transfer and flow structure in Rayleigh–Bénard convection." Journal of Fluid Mechanics 881 (October 24, 2019): 218–43. http://dx.doi.org/10.1017/jfm.2019.770.

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In Rayleigh–Bénard convection experiments, the thermal coupling between the sidewall and fluid is unavoidable. As a result, the thermal properties of the sidewall can influence the flow structure that develops. To get a better understanding of the influence of the sidewall, we performed a one-to-one comparison between experiments and direct numerical simulations (DNS) in aspect ratio (diameter over height) $\unicode[STIX]{x1D6E4}=1.00$ samples. We focus on the global heat transport, i.e. the Nusselt number $Nu$, and the local vertical temperature gradients near the horizontal mid-plane on the
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28

Elmestikawy, Hani, Victor Chéron, and Berend van Wachem. "On the influence of the periodic boundary conditions on the drag of random particle arrangements in PR-DNS." International Journal of Multiphase Flow 185 (April 2025): 105143. https://doi.org/10.1016/j.ijmultiphaseflow.2025.105143.

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29

Lluesma-Rodríguez, F., S. Hoyas та M. J. Perez-Quiles. "Influence of the computational domain on DNS of turbulent heat transfer up to Reτ=2000 for Pr=0.71". International Journal of Heat and Mass Transfer 122 (липень 2018): 983–92. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2018.02.047.

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30

Salehipour, H., W. R. Peltier, and A. Mashayek. "Turbulent diapycnal mixing in stratified shear flows: the influence of Prandtl number on mixing efficiency and transition at high Reynolds number." Journal of Fluid Mechanics 773 (May 20, 2015): 178–223. http://dx.doi.org/10.1017/jfm.2015.225.

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Motivated by the importance of small-scale turbulent diapycnal mixing to the closure of the large-scale meridional overturning circulation (MOC) of the oceans, we focus on a model problem which allows us to address the fundamental fluid mechanics that is expected to be characteristic of the oceanographic regime. Our model problem is one in which the initial conditions consist of a stably stratified parallel shear flow which evolves into the turbulent regime through the growth of a Kelvin–Helmholtz wave to finite amplitude followed by transition to turbulence. Through both linear stability anal
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31

Plumley, Meredith, Keith Julien, Philippe Marti, and Stephan Stellmach. "The effects of Ekman pumping on quasi-geostrophic Rayleigh–Bénard convection." Journal of Fluid Mechanics 803 (August 16, 2016): 51–71. http://dx.doi.org/10.1017/jfm.2016.452.

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Numerical simulations of three-dimensional rapidly rotating Rayleigh–Bénard convection are performed by employing an asymptotic quasi-geostrophic model that incorporates the effects of no-slip boundaries through (i) parametrized Ekman pumping boundary conditions and (ii) a thermal wind boundary layer that regularizes the enhanced thermal fluctuations induced by pumping. The fidelity of the model, obtained by an asymptotic reduction of the Navier–Stokes equations that implicitly enforces a pointwise geostrophic balance, is explored for the first time by comparisons of simulations against the fi
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32

Salehipour, Hesam, and W. R. Peltier. "Diapycnal diffusivity, turbulent Prandtl number and mixing efficiency in Boussinesq stratified turbulence." Journal of Fluid Mechanics 775 (June 26, 2015): 464–500. http://dx.doi.org/10.1017/jfm.2015.305.

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In order that it be correctly characterized, irreversible turbulent mixing in stratified fluids must distinguish between adiabatic ‘stirring’ and diabatic ‘mixing’. Such a distinction has been formalized through the definition of a diapycnal diffusivity, $K_{{\it\rho}}$ (Winters & D’Asaro, J. Fluid Mech., vol. 317, 1996, pp. 179–193) and an appropriate mixing efficiency, $\mathscr{E}$ (Caulfield & Peltier, J. Fluid Mech., vol. 413, 2000, pp. 1–47). Equivalent attention has not been paid to the definitions of a corresponding momentum diffusivity $K_{m}$ and hence an appropriately define
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33

Zhang, Xuan, and Oleg Zikanov. "Mixed convection in a horizontal duct with bottom heating and strong transverse magnetic field." Journal of Fluid Mechanics 757 (September 19, 2014): 33–56. http://dx.doi.org/10.1017/jfm.2014.473.

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AbstractMixed convection in a horizontal duct with imposed transverse horizontal magnetic field is studied using direct numerical simulations (DNS) and linear stability analysis. The duct’s walls are electrically insulated and thermally insulated with the exception of the bottom wall, at which constant-rate heating is applied. The focus of the study is on flows at high Hartmann ($\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\mat
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34

van der Poel, Erwin P., Roberto Verzicco, Siegfried Grossmann, and Detlef Lohse. "Plume emission statistics in turbulent Rayleigh–Bénard convection." Journal of Fluid Mechanics 772 (April 28, 2015): 5–15. http://dx.doi.org/10.1017/jfm.2015.176.

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Direct numerical simulations (DNS) of turbulent thermal convection in a $\mathit{Pr}=0.7$ fluid up to $\mathit{Ra}=10^{12}$ are used to study the statistics of thermal plumes. At various vertical locations in a cylindrical set-up with aspect ratio ${\it\Gamma}=\text{width}/\text{height}=1/3$, plumes are identified and their properties extracted. It is found that plumes are much less likely to be emitted from plate regions with large wind shear. Close to the plates, the plumes have a unimodal log–normal distribution, whereas at more central locations the distribution becomes weakly bimodal, whi
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35

Baharanchi, Ahmadreza Abbasi, Seckin Gokaltun, and George Dulikravich. "Performance improvement of existing drag models in two-fluid modeling of gas–solid flows using a PR-DNS based drag model." Powder Technology 286 (December 2015): 257–68. http://dx.doi.org/10.1016/j.powtec.2015.07.001.

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36

Luhar, M., A. S. Sharma, and B. J. McKeon. "On the structure and origin of pressure fluctuations in wall turbulence: predictions based on the resolvent analysis." Journal of Fluid Mechanics 751 (June 16, 2014): 38–70. http://dx.doi.org/10.1017/jfm.2014.283.

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AbstractWe generate predictions for the fluctuating pressure field in turbulent pipe flow by reformulating the resolvent analysis of McKeon and Sharma (J. Fluid Mech., vol. 658, 2010, pp. 336–382) in terms of the so-called primitive variables. Under this analysis, the nonlinear convective terms in the Fourier-transformed Navier–Stokes equations (NSE) are treated as a forcing that is mapped to a velocity and pressure response by the resolvent of the linearized Navier–Stokes operator. At each wavenumber–frequency combination, the turbulent velocity and pressure field are represented by the most-
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37

Wagner, Sebastian, and Olga Shishkina. "Heat flux enhancement by regular surface roughness in turbulent thermal convection." Journal of Fluid Mechanics 763 (December 11, 2014): 109–35. http://dx.doi.org/10.1017/jfm.2014.665.

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AbstractDirect numerical simulations (DNS) of turbulent thermal convection in a box-shaped domain with regular surface roughness at the heated bottom and cooled top surfaces are conducted for Prandtl number $\mathit{Pr}=0.786$ and Rayleigh numbers $\mathit{Ra}$ between $10^{6}$ and $10^{8}$. The surface roughness is introduced by four parallelepiped equidistantly distributed obstacles attached to the bottom plate, and four obstacles located symmetrically at the top plate. By varying $\mathit{Ra}$ and the height and width of the obstacles, we investigate the influence of the regular wall roughn
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38

Fu, Hao, Juan Chen, Yanjun Tong, et al. "New Nusselt Number Correlation and Turbulent Prandtl Number Model for Turbulent Convection with Liquid Metal Based on Quasi-DNS Results." Energies 18, no. 3 (2025): 547. https://doi.org/10.3390/en18030547.

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Liquid metal is widely used as the primary coolant in many advanced nuclear energy systems. Prandtl number of liquid metal is much lower than that of the conventional coolant of water or gas. Based on the Reynolds analogy, the turbulent Prandtl number is assumed to be a constant around unity. For the turbulent convection of liquid metal, dissipations of half the temperature variance are larger than those of turbulent kinetic energies. The dissimilarity between the thermal and momentum fields increases as Pr decreases. The turbulent Prandtl number is larger than one for the liquid metal. In the
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39

Rosevear, Madelaine G., Bishakhdatta Gayen, and Ross W. Griffiths. "Turbulent horizontal convection under spatially periodic forcing: a regime governed by interior inertia." Journal of Fluid Mechanics 831 (October 13, 2017): 491–523. http://dx.doi.org/10.1017/jfm.2017.640.

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Differential heating applied at a single horizontal boundary forces ‘horizontal convection’, even when there is no net heat flux through the boundary. However, almost all studies of horizontal convection have been limited to a special class of problem in which temperature or heat flux differences were applied in only one direction and over the horizontal length of a box (the Rossby problem; Rossby, Deep-Sea Res., vol. 12, 1965, pp. 9–16). These conditions strongly constrain the flow. Here we report laboratory experiments and direct numerical simulations (DNS) extending the results of Griffiths
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40

Deusebio, Enrico, G. Brethouwer, P. Schlatter, and E. Lindborg. "A numerical study of the unstratified and stratified Ekman layer." Journal of Fluid Mechanics 755 (August 26, 2014): 672–704. http://dx.doi.org/10.1017/jfm.2014.318.

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AbstractWe study the turbulent Ekman layer at moderately high Reynolds number, $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}1600 < \mathit{Re} = \delta _{E}G/\nu < 3000$, using direct numerical simulations (DNS). Here, $\delta _{E} = \sqrt{2\nu /f}$ is the laminar Ekman layer thickness, $G$ the geostrophic wind, $\nu $ the kinematic viscosity and $f$ is the Coriolis parameter. We present results for both neutrally, modera
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41

Sun, Bo, Sudheer Tenneti, Shankar Subramaniam, and Donald L. Koch. "Pseudo-turbulent heat flux and average gas–phase conduction during gas–solid heat transfer: flow past random fixed particle assemblies." Journal of Fluid Mechanics 798 (June 1, 2016): 299–349. http://dx.doi.org/10.1017/jfm.2016.290.

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Fluctuations in the gas-phase velocity can contribute significantly to the total gas-phase kinetic energy even in laminar gas–solid flows as shown by Mehrabadi et al. (J. Fluid Mech., vol. 770, 2015, pp. 210–246), and these pseudo-turbulent fluctuations can also enhance heat transfer in gas–solid flow. In this work, the pseudo-turbulent heat flux arising from temperature–velocity covariance, and average fluid-phase conduction during convective heat transfer in a gas–solid flow are quantified and modelled over a wide range of mean slip Reynolds number and solid volume fraction using particle-re
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42

Gayen, Bishakhdatta, Ross W. Griffiths, and Graham O. Hughes. "Stability transitions and turbulence in horizontal convection." Journal of Fluid Mechanics 751 (June 25, 2014): 698–724. http://dx.doi.org/10.1017/jfm.2014.302.

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AbstractRecent results have shown that convection forced by a temperature gradient along one horizontal boundary of a rectangular domain at a large Rayleigh number can be turbulent in parts of the flow field. However, the conditions for onset of turbulence, the dependence of flow and heat transport on Rayleigh number, and the roles of large and small scales in the flow, have not been established. We use three-dimensional direct numerical simulation (DNS) and large-eddy simulation (LES) over a wide range of Rayleigh numbers,$\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le
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43

TRIAS, F. X., M. SORIA, A. OLIVA, and C. D. PÉREZ-SEGARRA. "Direct numerical simulations of two- and three-dimensional turbulent natural convection flows in a differentially heated cavity of aspect ratio 4." Journal of Fluid Mechanics 586 (August 14, 2007): 259–93. http://dx.doi.org/10.1017/s0022112007006908.

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A set of complete two- and three-dimensional direct numerical simulations (DNS) in a differentially heated air-filled cavity of aspect ratio 4 with adiabatic horizontal walls is presented in this paper. Although the physical phenomenon is three-dimensional, owing to its prohibitive computational costs the majority of the previous DNS of turbulent and transition natural convection flows in enclosed cavities assumed a two-dimensional behaviour. The configurations selected here (Rayleigh number based on the cavity height 6.4 × 108, 2 × 109 and 1010, Pr = 0.71) are an extension to three dimensions
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44

Ibe, Akihiro, Kazuo Saito, Mitsuo Nakazato, Yoko Kikuchi, Kenji Fujinuma, and Taichiro Nishima. "Quantitative Determination of Amines in Wine by Liquid Chromatography." Journal of AOAC INTERNATIONAL 74, no. 4 (1991): 695–98. http://dx.doi.org/10.1093/jaoac/74.4.695.

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Abstract A liquid chromatographic (LC) procedure is described for the determination by dansylation of the following 16 kinds of biogenic amines found In wine: monomethylamine (MM), ethylamine (EM), iso- and n-propylamlne (Pr), iso- and n-butylamine (Bu), iso- and n-amylamlne (Am), pyrrolidine (PY), 2- phenethylamine (PH), tryptamine (TR), putresclne (PU), cadaverine (CA), histamine (HI), tyramine (TY), and spermidine (SP). The amines In white and red wine were applied to a column of Amberllte CG-50 type I resin (Na-form) after the column had been washed with water and eluted with 1N hydrochlor
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45

Varaksin, Aleksey Yu, and Sergei V. Ryzhkov. "Mathematical Modeling of Gas-Solid Two-Phase Flows: Problems, Achievements and Perspectives (A Review)." Mathematics 11, no. 15 (2023): 3290. http://dx.doi.org/10.3390/math11153290.

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Mathematical modeling is the most important tool for constructing theories of different kinds of two-phase flows. This review is devoted to the analysis of the introduction of mathematical modeling to two-phase flows, where solid particles mainly serve as the dispersed phase. The main problems and features of the study of gas-solid two-phase flows are included. The main characteristics of gas flows with solid particles are discussed, and the classification of two-phase flows is developed based on these characteristics. The Lagrangian and Euler approaches to modeling the motion of a dispersed p
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46

Biferale, L., A. S. Lanotte, R. Scatamacchia, and F. Toschi. "Intermittency in the relative separations of tracers and of heavy particles in turbulent flows." Journal of Fluid Mechanics 757 (September 23, 2014): 550–72. http://dx.doi.org/10.1017/jfm.2014.515.

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AbstractResults from direct numerical simulations (DNS) of particle relative dispersion in three-dimensional homogeneous and isotropic turbulence at Reynolds number $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}{\mathit{Re}}_{\lambda } \sim 300$ are presented. We study point-like passive tracers and heavy particles, at Stokes number $\mathit{St}=0.6,1$ and 5. Particles are emitted from localised sources, in bunches of thousands,
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47

Horn, Susanne, and Olga Shishkina. "Toroidal and poloidal energy in rotating Rayleigh–Bénard convection." Journal of Fluid Mechanics 762 (December 2, 2014): 232–55. http://dx.doi.org/10.1017/jfm.2014.652.

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AbstractWe consider rotating Rayleigh–Bénard convection of a fluid with a Prandtl number of $\mathit{Pr}=0.8$ in a cylindrical cell with an aspect ratio ${\it\Gamma}=1/2$. Direct numerical simulations (DNS) were performed for the Rayleigh number range $10^{5}\leqslant \mathit{Ra}\leqslant 10^{9}$ and the inverse Rossby number range $0\leqslant 1/\mathit{Ro}\leqslant 20$. We propose a method to capture regime transitions based on the decomposition of the velocity field into toroidal and poloidal parts. We identify four different regimes. First, a buoyancy-dominated regime occurring while the to
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48

Pagliarini, L., R. Corsini, E. Stalio, and F. Bozzoli. "RANS representation of transition and separation over a low-Re number blade section at high angle of attack." Journal of Physics: Conference Series 2766, no. 1 (2024): 012086. http://dx.doi.org/10.1088/1742-6596/2766/1/012086.

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Abstract Systems based on wind energy harvesting can successfully meet part of the increasing green energy demand worldwide. However, wind turbines operation might be undermined by varying atmospheric conditions, which could result in an increase of angle of attack and consequent onset of flow separation phenomena, especially at low Reynolds numbers. Such conditions are strongly influenced by blades geometry, and they negatively affect structural integrity and power output of wind turbines. For this reason, it is crucial to define a tool capable of swiftly allowing numerical investigations on
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49

Masi, Enrica, Josette Bellan, Kenneth G. Harstad, and Nora A. Okong’o. "Multi-species turbulent mixing under supercritical-pressure conditions: modelling, direct numerical simulation and analysis revealing species spinodal decomposition." Journal of Fluid Mechanics 721 (March 19, 2013): 578–626. http://dx.doi.org/10.1017/jfm.2013.70.

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AbstractA model is developed for describing mixing of several species under high-pressure conditions. The model includes the Peng–Robinson equation of state, a full mass-diffusion matrix, a full thermal-diffusion-factor matrix necessary to incorporate the Soret and Dufour effects and both thermal conductivity and viscosity computed for the species mixture using mixing rules. Direct numerical simulations (DNSs) are conducted in a temporal mixing layer configuration. The initial mean flow is perturbed using an analytical perturbation which is consistent with the definition of vorticity and is di
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50

Ahlers, Guenter, Eberhard Bodenschatz, and Xiaozhou He. "Logarithmic temperature profiles of turbulent Rayleigh–Bénard convection in the classical and ultimate state for a Prandtl number of 0.8." Journal of Fluid Mechanics 758 (October 9, 2014): 436–67. http://dx.doi.org/10.1017/jfm.2014.543.

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AbstractWe report on experimental determinations of the temperature field in the interior (bulk) of turbulent Rayleigh–Bénard convection for a cylindrical sample with an aspect ratio (diameter $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}D$ over height $L$) equal to 0.50, in both the classical and the ultimate state. The measurements are for Rayleigh numbers $\mathit{Ra}$ from $6\times 10^{11}$ to $10^{13}$ in the classical and
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