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direct numerical simulation of turbulent boundary layer with heat transfer

INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2016年 99卷 10-19页

作者： Zhao, Hui Wei, Anyang Luo, Kun Fan, Jianren Zhejiang Univ State Key Lab Clean Energy Utilizat 38 Zheda Rd Hangzhou 310027 Zhejiang Peoples R China

A direct numerical simulation was conducted of an incompressible, nominally zero-pressure-gradient flat-plate boundary layer from momentum thickness Reynolds numbers 80-1150. Heat transfer was considered with a constant-temperature solid boundary and the Prandtl number Pr = 0.71. Both the temperature boundary layer thickness and the Stanton number compared well to experimental data. The mean temperature distributions, the root-mean-square of the temperature fluctuations and the correlations between the velocity fluctuations and the temperature fluctuations have good agreements with previous investigations. One of the main focuses of the present paper is the statistical behavior of the velocity and temperature fluctuations in the wall-normal direction from the sub-layer region to the outer region of the boundary layer. Probability density functions (PDF) are presented to investigate the statistical characteristics near the wall. In addition, the near-wall temperature streaky structures are presented, and the coherence of the turbulent structures between the velocity and the temperature fields is discussed. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： direct numerical simulation Turbulent boundary layer Heat transfer Probability density function Turbulent structures

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direct numerical simulation of an oscillating droplet in partial contact with a substrate

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COMPUTERS & FLUIDS 2013年 77卷 152-158页

作者： Olgac, Ufuk Izbassarov, Daulet Muradoglu, Metin Koc Univ Dept Mech Engn TR-34450 Istanbul Turkey

Small-amplitude oscillations of a viscous drop that is in a partial contact with a flat substrate are investigated computationally using a finite-difference/front-tracking method. Emphasis is placed on the first mode resonance frequency response of the droplet for a wide range of contact angles. It is found that numerical results converge to the theoretical predictions of Strani and Sabetta (Strani M, Sabetta F. J Fluid Mech 1984;141:223-47) for high contact angles, whereas considerable discrepancy is observed as contact angle decreases. However, the dependence of the frequency on the drop radius, drop density and surface tension coefficient remains the same as predicted by the Strani and Sabetta theory. It is also found that the effects of density and viscosity ratio become insignificant for the density and viscosity ratios larger than 10. The oscillations are found to be damped exponentially in time due to viscous dissipation similar to the case of an isolated droplet and the damping rate decreases with increasing contact angle. (c) 2013 Elsevier Ltd. All rights reserved.

关键词： Drop oscillation Interfacial flows Front-tracking method direct numerical simulation

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direct numerical simulation of a high-pressure turbulent reacting temporal mixing layer

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COMBUSTION AND FLAME 2017年 176卷 245-262页

作者： Bellan, Josette CALTECH Pasadena CA 91125 USA CALTECH Jet Prop Lab 4800 Oak Grove Dr Pasadena CA 91109 USA

direct numerical simulation realizations were created of a temporal mixing layer in which combustion occurs under high-pressure (high-p) turbulent conditions. The model combines the formulation of Masi, et al. (2013) for describing multi-species mixing under high-p conditions and a single-step chemical reaction of rate consistent with ignition prediction (Borghesi, and Bellan, 2015). In each simulation the computations are pursued past a time at which a maximum average-volumetric p is attained;most analysis is performed at this time, t(pp)(*). The ensemble of realizations explores the effect of the initial Reynolds number, Re-0, of the initial pressure, p(0), and of the initial composition of the two mixing-layer streams. The results show that the thermodynamic energy added by the reaction at the small scales is partially dissipated and partially backscattered. The formation of turbulent small scales is initiated by the morphological changes in the flow through stretching and twisting rather than vice versa. The reaction establishes primarily in the oxidizer stream and is preponderantly of diffusion type. Overwhelmingly, the higher reaction rates occur in the diffusion flame, particularly in regions of high density-gradient magnitude. At higher po the reaction rate reaches higher values and occurs in regions of higher density gradients. The range of reaction rates is independent of the Re-0 value but the magnitude of the density gradients increases with Re-0. When H2O and CO2 are initially present, uphill diffusion dominates over regular diffusion and occurs in regions of smaller density-gradient magnitude whereas regular diffusion occurs in regions of larger density-gradient magnitude where the reaction is more vigorous. H2O is more prone than CO2 to regular diffusion in the larger density-gradient magnitude regions. When H2O and CO2 only form in the flame, both H2O and CO2 are subject to regular diffusion over the entire range of density-gradient values. The dissi

关键词： High-pressure combustion Uphill diffusion during high-pressure combustion Flame index at high pressure direct numerical simulation

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direct numerical-simulation OF A TURBULENT-FLOW IN A CHANNEL HAVING PERIODIC PRESSURE-GRADIENT

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INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW 1995年第5期16卷 333-340页

作者： MIYAKE, Y TSUJIMOTO, K BEPPU, H Department of Mechanical Engineering Osaka University Osaka Japan

The intent of this paper is to contribute database information for a flow less complicated than a backward step flow and less simple than a flat channel flow, demonstrating the influence of pressure gradient in an internal flow and serving to stimulate the creation of new improved turbulence models. A direct numerical simulation (DNS) was conducted for a turbulent channel flow having a periodic pressure gradient;i.e., a channel having flat plate walls, a solid one on one side and a porous one on the other side, which allows variable strength injection/suction of fluid. The Reynolds number based on the mean friction velocity on the two walls and the half width of the flow passage is 300. The mean flow field as well as such statistical quantities of turbulence as fluctuation velocities, and Reynolds stresses are presented, with a discussion of the influence of the periodic pressure gradient. The energy budget for the transport equations for the turbulent stresses is also included. The momentum balance is given in sections normal to the mean flow. It is demonstrated that although the thin layer approximation is valid, the pressure gradient effect in this flow is different from that in a boundary-layer flow.

关键词： CHANNEL FLOW TURBULENCE PRESSURE GRADIENT direct numerical simulation DATABASE TURBULENCE MODELS

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direct numerical simulation OF THE TRANSITION TO TURBULENCE IN A SUPERSONIC BOUNDARY LAYER ON SMOOTH AND ROUGH SURFACES

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JOURNAL OF APPLIED MECHANICS AND TECHNICAL PHYSICS 2017年第5期58卷 826-836页

作者： Khotyanovsky, D. V. Kudryavtsev, A. N. Russian Acad Sci Siberian Branch Khristianovich Inst Theoret & Appl Mech Novosibirsk 630090 Russia

direct numerical simulations of instability development and transition to turbulence in a supersonic boundary layer on a flat plate are performed. The computations are carried out for moderate supersonic (free-stream Mach number M = 2) and hypersonic (M = 6) velocities. The boundary layer development is simulated, which includes the stages of linear growth of disturbances, their nonlinear interaction, stochastization, and turbulent flow formation. A laminar-turbulent transition initiated by distributed roughness of the plate surface at the Mach number M = 2 is also considered.

关键词： direct numerical simulation laminar-turbulent transition supersonic boundary layer distributed roughness

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direct numerical simulation of particle interaction with ejections in turbulent channel flows

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INTERNATIONAL JOURNAL OF MULTIPHASE FLOW 2011年第2期37卷 187-197页

作者： Vinkovic, I. Doppler, D. Lelouvetel, J. Buffat, M. Univ Lyon 1 INSA Lyon Ecole Cent Lyon CNRS UMR 5509Lab Mecan Fluides & Acoust F-69134 Ecully France Keio Univ Fac Sci & Technol Dept Syst Design Engn Kohoku Ku Yokohama Kanagawa 2238522 Japan

direct numerical simulations (DNS) of incompressible turbulent channel flows coupled with Lagrangian particle tracking are performed to study the characteristics of ejections that surround solid particles. The behavior of particles in dilute turbulent channel flows, without particle collisions and without feedback of particles on the carrier fluid, is studied using high Reynolds number DNS (Re = 12,500). The results show that particles moving away from the wall are surrounded by ejections, confirming previous studies on this issue. A threshold value separating ejections with only upward moving particles is established. When normalized by the square root of the Stokes number and the square of the friction velocity, the threshold profiles follow the same qualitative trends, for all the parameters tested in this study, in the range of the experiments. When compared to suspension thresholds proposed by other studies in the Shields diagram, our simulations predict a much larger value because of the measure used to characterize the fluid and the criterion chosen to decide whether particles are influenced by the surrounding fluid. However, for intermediate particle Reynolds numbers, the threshold proposed here is in fair agreement with the theoretical criterion proposed by Bagnold (1966) [Bagnold, R., 1966. Geological Survey Professional Paper, vol. 422-1]. Nevertheless, further studies will be conducted to understand the normalization of the threshold. (C) 2010 Elsevier Ltd. All rights reserved.

关键词： direct numerical simulation Lagrangian particle tracking Turbulent channel flow Quadrant analysis Threshold

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direct numerical simulation of a turbulent Couette-Poiseuille flow: Turbulent statistics

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INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW 2018年 72卷 288-303页

作者： Hoon, Kim Jung Hwa, Lee Jae UNIST Dept Mech Engn 50 UNIST Gil Ulsan 44919 South Korea

The direct numerical simulation of a fully developed turbulent Couette-Poiseuille flow is performed to investigate the modification of turbulent statistics on the bottom and top walls compared to those in a pure Poiseuille flow. The streamwise mean velocity profile shows that an extended logarithmic layer for a Couette-Poiseuille flow is developed from each wall to the centerline. In addition, the turbulent intensities and Reynolds shear stress on the bottom wall are found to be larger than those in the Poiseuille flow, whereas it is reversed on the top wall due to reduction of the velocity shear. The quadrant analysis of the Reynolds shear stress reveals that large Q2 and Q4 event motions are continuously created throughout the entire flow near the centerline, leading to active momentum transport between the bottom and top walls for the C-type. Inspection of the pre-multiplied streamwise and spanwise energy spectra shows that distinct secondary outer peaks are created for all velocity components and a plateau, called the k(x)(-1) region, is presented in the logarithmic region. Based on an analysis of the net force spectra, three spectral ranges in the wavelength space, corresponding to small-(lambda(x)/delta <= 1), large- (1 <= lambda(x)/delta <= 1) and very-large-scale (lambda(x)/delta >= 1) motions for a Couette-Poiseuille flow, are proposed, and very-large-scale structures are highly energetic and contribute more than half of the streamwise turbulent kinetic energy and Reynolds shear stress, where lambda(x) is the streamwise wavelength and delta is the channel half height.

关键词： Turbulent Couette-Poiseuille flow direct numerical simulation

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direct numerical simulation of turbulent Taylor-Couette flow

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JOURNAL OF FLUID MECHANICS 2007年 587卷 373-393页

作者： Dong, S. Purdue Univ Ctr Computat & Appl Math Dept Math W Lafayette IN 47907 USA

We investigate the dynamical and statistical features of turbulent Taylor-Couette flow (for a radius ratio 0.5) through three-dimensional direct numerical simulations (DNS) at Reynolds numbers ranging from 1000 to 8000. We show that in three-dimensional space the Gortler vortices are randomly distributed in banded regions on the wall, concentrating at the outflow boundaries of Taylor vortex cells, which spread over the entire cylinder surface with increasing Reynolds number. Gortler vortices cause streaky structures that form herringbone-like patterns near the wall. For the Reynolds numbers studied here, the average axial spacing of the streaks is approximately 100 viscous wall units, and the average tilting angle ranges from 16 degrees to 20 degrees. simulation results have been compared to the experimental data in the literature, and the flow dynamics and statistics are discussed in detail.

关键词： direct numerical simulation

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direct numerical simulation of the effect of an electric field on flame stability

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COMBUSTION AND FLAME 2010年第12期157卷 2286-2297页

作者： Belhi, Memdouh Domingo, Pascale Vervisch, Pierre CORIA CNRS F-76801 St Etienne France INSA Rouen F-76801 St Etienne France

The role of electric fields in stabilising combustion is a well-known phenomenon. Among the possible mechanisms favouring the anchorage of the flame base, the ion-driven wind acting directly on flow momentum ahead of the flame base could be the leading one. direct numerical simulation has been used to verify this hypothesis and lead to a better understanding of diffusion flame base anchoring in the presence of an externally applied voltage. In this context, a simplified modelling approach is proposed to describe combustion in the presence of electric body forces. The model reproduces the tendencies of experimental observations found in the literature. The sensitivity of the flame lift-off height to the applied voltage is studied and the modification of the velocity field ahead of the flame base induced by the electric volume forces is highlighted. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

关键词： Flame stability Electric field Ionic wind direct numerical simulation

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direct numerical simulation of turbulent channel flows using a stabilized finite element method

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COMPUTERS & FLUIDS 2009年第4期38卷 924-938页

作者： Trofimova, Alisa V. Tejada-Martinez, Andres E. Jansen, Kenneth E. Lahey, Richard T., Jr. Univ S Florida Dept Civil & Environm Engn Tampa FL 33620 USA Rensselaer Polytech Inst Dept Mech Aerosp & Nucl Engn Troy NY 12180 USA

direct numerical simulations (DNS) of incompressible turbulent channel flows at Re-tau = 180 and 395 (i.e., Reynolds number, based on the friction velocity and channel half-width) were performed using a stabilized finite element method (FEM). These simulations have been motivated by the fact that the use of stabilized finite element methods for DNS and LES is fairly recent and thus the question of how accurately these methods capture the wide range of scales in a turbulent flow remains open. To help address this question. we present converged results of turbulent channel flows under statistical equilibrium in terms of mean velocity, mean shear stresses, root mean square velocity fluctuations, autocorrelation coefficients, one-dimensional energy spectra and balances of the transport equation for turbulent kinetic energy. These results are consistent with previously published DNS results based on a pseudo-spectral method, thereby demonstrating the accuracy of the stabilized FEM for turbulence simulations. (C) 2009 Published by Elsevier Ltd.

关键词： direct numerical simulation

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