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direct numerical simulation study of the interaction between the polymer effect and velocity gradient tensor in decaying homogeneous isotropic turbulence

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Chinese Physics B 2011年第12期20卷 279-292页

作者：蔡伟华李凤臣张红娜 School of Energy Science and Engineering Harbin Institute of Technology

direct numerical simulation of decaying homogeneous isotropic turbulence （DHIT） of a polymer solution is performed. In order to understand the polymer effect on turbulence or additive-turbulence interaction, we directly investigate the influence of polymers on velocity gradient tensor including vorticity and strain. By visualizing vortex tubes and sheets, we observe a remarkable inhibition of vortex structures in an intermediate-scale field and a small-scale field but not for a large scale field in DHIT with polymers. The geometric study indicates a strong relevance among the vorticity vector, rate-of-strain tensor, and polymer conformation tensor. Joint probability density functions show that the polymer effect can increase ＂strain generation resistance＂ and ＂vorticity generation resistance＂, i.e., inhibit the generation of vortex sheets and tubes, ultimately leading to turbulence inhibition effects.

关键词： decaying homogeneous isotropic turbulence turbulent drag-reducing flow velocity gradient tensor direct numerical simulation

direct numerical simulation OF TURBULENT FLOW IN A STRAIGHT SQUARE DUCT AT REYNOLDS NUMBER 600

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Journal of Hydrodynamics 2009年第5期21卷 600-607页

作者： ZHU Zuo-jin YANG Hong-xing CHEN Ting-yao Multiphase Reactive Flow Division Department of Thermal Science and Energy Engineering University of Science and Technology of China Hefei 230026 China Department of Building Services Engineering The Hong Kong Polytechnic University Hong Kong China

This article presents the direct numerical simulation results of the turbulent flow in a straight square duct at a Reynolds number of 600, based on the duct width and the mean wall-shear velocity. The turbulence statistics along the wall bisector is examined with the turbulent flow field properties given by streamwise velocity and vorticity fields in the duct cross section. It was found that the solutions of the turbulent duct flow obtained in a spatial resolution with 1.2×10^6 grid points are satisfactory as compared to the existing numerical and experimental results. The results indicate that it is reasonable to neglect the sub-grid scale models in this spatial resolution level for the duct flow at the particular friction Reynolds number.

关键词： straight square duct turbulent flow direct numerical simulation

direct numerical simulation of the Pulsed Arc Discharge in Supersonic Compression Ramp Flow

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Journal of Thermal Science 2020年第6期29卷 1581-1593页

作者： SONG Guoxing LI Jun TANG Mengxiao Aeronautics Engineering College Air Force Engineering UniversityXi’an 710038China

direct numerical simulation(DNS)of shock wave/turbulent boundary layer interaction(SWTBLI)with pulsed arc discharge is carried out in this *** subject in the study is a Ma=2.9 compression flow over a 24-degree *** numerical approaches were validated by the experimental results in the same flow *** heat source model was added to the Navier-Stokes equation to serve as the energy deposition of the pulsed arc *** streamwise locations are selected to apply energy *** effect of the pulsed arc discharge on the ramp-induced flow separation has been studied in *** DNS results demonstrate the incentive locations play a dominant role in suppressing the separated *** show that pulsed heating is characterized by a thermal blockage,which leads to streamwise *** incentive locations upstream the interaction zone of the base flow have a better control *** separation bubble shape shows as"spikes",and the downstream flow of the heated region is accelerated due to the momentum exchange between the upper boundary layer and the bottom boundary *** high-speed upper fluid is transferred to the bottom,and thus enhances its ability to resist the flow *** stripe vortex structures are also generated at the edge of the ***,the turbulent kinetic disturbance energy is increased in the flow *** disturbances that originate from the pulsed heating are capable of increasing the turbulent intensity and then diminishing the trend of flow separation.

关键词： direct numerical simulation pulsed arc discharge shock waves turbulent boundary layer flow separation

direct numerical simulation of elastic turbulence and its mixing-enhancement effect in a straight channel flow

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Chinese Physics B 2013年第2期22卷 320-327页

作者：张红娜李凤臣曹阳 Kunugi Tomoaki 宇波 School of Energy Science and Engineering Harbin Institute of Technology Department of Nuclear Engineering Kyoto University Beijing Key Laboratory of Urban Oil and Gas Distribution Technology China University of Petroleum-Beijing

In this paper,we present a direct numerical simulation（DNS） of elastic turbulence of viscoelastic fluid at vanishingly low Reynolds number（Re = 1） in a three-dimensional straight channel flow for the first time,using the Giesekus constitutive model for the *** order to generate and maintain the turbulent fluid motion in the straight channel,a sinusoidal force term is added to the momentum equation,and then the elastic turbulence is numerically realized with an initialized chaotic velocity field and a stretched conformation *** and structural characteristics of the elastic turbulence therein are analyzed based on the detailed information obtained from the *** fluid mixing enhancement effect of elastic turbulence is also demonstrated for the potential applications of this phenomenon.

关键词： elastic turbulence viscoelastic fluid direct numerical simulation mixing enhancement

direct numerical simulation of shock wave/boundary layer interaction controlled by steady microjet in a compression ramp

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Chinese Journal of Aeronautics 2024年第10期37卷 83-102页

作者： Ruoye XIAO Dong SUN Jian YU School of Aeronautic Science and Engineering Beihang UniversityBeijing 100191China State Key Laboratory of Aerodynamics Mianyang 621000China

Shock wave/boundary layer interaction in a 24°turning angle of the compression ramp at Mach number 2.9 controlled by steady microjet is investigated using direct numerical *** different jet spacings which are termed as sparse,moderate and dense are considered,and the induced vortex system and shock structures are compared.A moderate jet spacing configuration is found to generate counter-rotating vortex pairs that transport high-momentum fluid towards the vicinity of wall and strengthen the boundary layer to resist separation,reducing the separation *** dense jet spacing configuration creates a larger momentum deficit region,reducing the friction downstream of the *** of pressure and pressure gradient reveals that dense jet spacing configuration reduces the intensity of separation *** impact of varying jet spacings on the turbulent kinetic energy transport mechanism is also investigated by decomposing the budget terms in the transport ***,the spectral characteristics of the separation region are studied using power spectral density and dynamic mode decomposition methods,revealing that moderate jet spacing configuration suppresses low-frequency fluctuations in the separation region.

关键词： Shock wave/boundary layer interaction Compression ramp Steady microjet Different jet spacings direct numerical simulation

direct numerical simulation of Open Von Kármán Swirling Flow

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Journal of Hydrodynamics 2014年第2期26卷 165-177页

作者： XING Tao Department of Mechanical Engineering College of EngineeringUniversity of Idaho

direct numerical simulations are used to investigate the Open Von Kfirmfin Swirling Flow, a new type of unsteady three-dimensional flow that is formed between two counter-rotating coaxial disks with an axial extraction enclosed by a cylinder chamber. Solution verification shows that monotonic convergence is achieved on three systematically refined grids for average pressure at the disk periphery with a small grid uncertainty at 3.5%. Effects of the rotational speeds and flow rates on the flow field are examined. When the disks are rotating at the lowest speed, ＋100 RPM, only circular vortices are formed regardless of the flow rates. When the disks are rotating at ＋300 RPM and ＋500 RPM, negative spiral vortex network is formed. The radial counterflow concept for such spiral vortex network is verified by examining various horizontal cuts and radial velocity component, which show radial outflows in two bands near the two disks and radial inflow in one band between them. Overall, the flow is similar to the Stewartson type flow but with significant differences for all three velocity components due to the axial suction at the upper disk center and gap between the disk periphery and chamber wall.

关键词： direct numerical simulation Open Von Kfirmfin flow swirling radial counterflow

direct numerical simulation of impinging shock wave and turbulent boundary layer interaction over a wavy-wall

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Chinese Journal of Aeronautics 2021年第5期34卷 350-363页

作者： Fulin TONG Dong SUN Xinliang LI LHD Institute of MechanicsChinese Academy of SciencesBeijing 100190China State Key Laboratory of Aerodynamics China Aerodynamics Research and Development CenterMianvang 621000China Computational Aerodynamics Institute China Aerodynamics Research and Development CenterMicmyang 621000China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China

The interaction of an impinging oblique shock wave with an angle of 30°and a supersonic turbulent boundary layer at Ma_(∞)=2.9 and Re_(θ)=2400 over a wavy-wall is investigated through direct numerical simulation and compared with the interaction on a flat-plate under the same flow conditions.A sinusoidal wave with amplitude to wavelength ratio of 0.26 moves in the streamwise direction and is uniformly distributed across the spanwise *** influences of the wavy-wall on the interaction,including the characterization of the flow field,the skin-friction,pressure and the budget of turbulence kinetic energy,are systematically *** region of separation grows slightly and decomposes into four *** peaks of skin-friction are observed at the rear part of the interaction *** low-frequency shock motion can be seen in the wall pressure *** of the turbulence kinetic energy budget indicate that both diffusion and transport significantly increase near the crests,balanced by an amplified dissipation in the near-wall *** orthogonal decomposition analyses show that the most energetic structures are associated with the separated shock and the shear layer over the *** the bubbles in the first two troughs are dominated by a low-frequency enlargement or shrinkage.

关键词： direct numerical simulation Low-frequency unsteadiness Shock waves Turbulent boundary layer Wavy-wall

direct numerical simulation of Three-Dimensional Richtmyer-Meshkov Instability

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Chinese Physics Letters 2008年第1期25卷 188-190页

作者：傅德薰马延文李新亮 State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Beijing 100080

direct numerical simulation （DNS） is used to study flow characteristics after interaction of a planar shock with a spherical media interface in each side of which the density is different. This interracial instability is known as the Richtmyer-Meshkov （R-M） instability. The compressible Navier-Stoke equations are discretized with group velocity control （GVC） modified fourth order accurate compact difference scheme. Three-dimensional numerical simulations are performed for R-M instability installed passing a shock through a spherical interface. Based on numerical results the characteristics of 3D R-M instability are analysed. The evaluation for distortion of the interface, the deformation of the incident shock wave and effects of refraction, reflection and diffraction are presented. The effects of the interracial instability on produced vorticity and mixing is discussed.

关键词： direct numerical simulation Three-Dimensional Richtmyer-Meshkov Instability group velocity control (GVC)

direct numerical simulation of Gas-Solid Two-Phase Mixing Layer

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Journal of Thermal Science 2005年第1期14卷 41-47页

作者： WenchunLI GuilinHU ZheZHOU JianrenFAN KefaCEN InstituteforThermalPowerEngineeringandCleanEnergyandEnvironmentalEngineering ZhejiangUniversityHangzhou310027China

In this paper, the spatially evolving of the higher Reynolds numbers gas-solid mixing layer under compressible conditions was investigated by a new direct numerical simulation technology. A high-resolution solver was performed for the gas-phase flow-field, particles with different Stokes numbers were traced by the Lagrangian approach based on one-way coupling. The processes of the vortex rolling up and pairing in the two-dimensional mixing layer were captured precisely. The large-scale structures developed from the initial inflow are characterized by the counter-rotating vortices. The mean velocity and the fluctuation intensities profiles agree well with the experimental data. Particles with smaller Stokes numbers accumulate at the vortex centers due to the smaller aerodynamic response time; particles with moderate Stokes numbers tend to orbit around individual streamwise vortices and in the periphery of paring vortices; particles with larger Stokes numbers disperse less evenly, showing a concentration distribution in the flow field.

关键词： direct numerical simulation gas-solid mixing layer vortex particle dispersion.