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A boundary layer model for capture of inclusions by steel-slag interface in a turbulent flow

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Journal of Iron and Steel Research(International) 2023年第6期30卷 1101-1108页

作者： Yi-peng Sun Hao-jian Duan Li-feng Zhang School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China School of Mechanical and Materials Engineering North China University of TechnologyBeijing 100144China

A boundary layer model was developed to predict the capture of inclusions by steel-slag interface in a turbulent fluid flow,which is based on the detailed analysis of inclusion trajectories.The effective boundary layer for inclusion removal was proposed by a statistical method.It is noticed that the capture of inclusions by steel-slag interface is not only dependent on the diameter of inclusions but also related to the local turbulent conditions.In high turbulent flow fields,the transport of inclusions is mainly dominated by the turbulent flow,and thus,the effective boundary layer thickness is mainly affected by the level of turbulent kinetic energy and is almost independent of the inclusion diameter.The inertia of inclusions gradually takes over the stochastic effect of turbulent flow,and the effect of inclusion diameter on effective boundary layer thickness becomes more noticeable with the decrease in the level of turbulent kinetic energy.Besides,the effective boundary layer thickness is more susceptible to the inclusion diameter for larger inclusions due to its greater inertia under the same turbulent condition while it principally depends on the level of turbulent kinetic energy for smaller inclusions.As the characteristic velocity increases,the time for inclusions transport and interaction with steel-slag interface decreases,and thus,the effective boundary layer thickness decreases.Moreover,the graphical user interface was developed by using the cubic spline interpolation for ease of coupling the current boundary layer model with the macro-scale model of a turbulent fluid flow in the metallurgical vessel.

关键词： Boundary layer model Capture of inclusions steel–slag interface turbulent flow

凹陷窝深度对矩形通道内煤油流动与传热性能的影响研究

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Acta Mechanica Sinica 2022年第6期38卷 69-80,I0002页

作者：李冼杜蒙蒙仲峰泉 State Key Laboratory of High Temperature Gas Dynamics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China

摘要本文通过数值仿真研究了凹陷窝深度和煤油物性的变化对带有圆形凹陷窝的小尺度矩形通道内湍流流动及对流换热的耦合影响.基于雷诺平均方法并结合SST k-ω湍流模型和煤油10组分替代模型,获得了不同深度圆形凹陷窝的旋涡结构及传热特... 详细信息

摘要本文通过数值仿真研究了凹陷窝深度和煤油物性的变化对带有圆形凹陷窝的小尺度矩形通道内湍流流动及对流换热的耦合影响.基于雷诺平均方法并结合SST k-ω湍流模型和煤油10组分替代模型,获得了不同深度圆形凹陷窝的旋涡结构及传热特性.计算结果表明,凹陷窝能够产生复杂的三维旋涡结构,明显改变了局部的湍流流动,从而导致壁面不同位置处的对流传热性能得到强化或者削弱.研究发现,随着凹陷窝深度的增加,壁面的平均努塞尔数先逐渐增大,当深度到达某一定值后,努塞尔数减小.根据流场的变化可知,当旋涡结构为马蹄涡和龙卷风涡时,带凹陷窝壁面的传热明显增强;而随着凹陷窝深度的进一步增加,旋涡结构变为非对称的羊角涡,导致传热性能下降.与努塞尔数的变化类似,摩擦因子同样随着凹陷窝深度的增加呈现先增大后减小的变化规律.

关键词： Dimple depth Kerosene Convective heat transfer turbulent flow

Numerical investigation of velocity distribution of turbulent flow through vertically double-layered vegetation

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Water Science and Engineering 2019年第4期12卷 319-329页

作者： Naveed Anjum Norio Tanaka Graduate School of Science and Engineering Saitama UniversitySaitama 338-8570Japan International Institute for Resilient Society Saitama UniversitySaitama 338-8570Japan

The velocity structures of flow through vertically double-layered vegetation(VDLV)as well as single-layered rigid vegetation(SLV)were investigated computationally with a three-dimensional(3D)Reynolds stress turbulence model,using the computational fluid dynamics(CFD)code FLUENT.The detailed velocity distribution was explored with a varying initial Froude number(Fr),with consideration of the steady subcritical flow conditions of an inland tsunami.In VDLV flows,the numerical model successfully captured the inflection point in the profiles of mean streamwise velocities in the mixing-layer region around the top of short submerged vegetation.An upward and downward movement of flow occurred at the positions located just behind the tall and short vegetation,respectively.Overall,higher streamwise velocities were observed in the upper vegetation layer due to high porosity,with Pr=98%(sparse vegetation,where Pr is the porosity),as compared to those in the lower vegetation layer,which had comparatively low porosity,with Pr=91%(dense vegetation).A rising trend of velocities was found as the flow passed through the vegetation region,followed by a clear sawtooth distribution,as compared to the regions just upstream and downstream of vegetation where the flow was almost uniform.In VDLV flows,a rising trend in the flow resistance was observed with the increase in the initial Froude number,i.e.,Fr?0.67,0.70,and 0.73.However,the flow resistance in the case of SLV was relatively very low.The numerical results also show the flow structures within the vicinity of short and tall vegetation,which are difficult to attain through experimental measurements.

关键词： Vertically double-layered vegetation Single-layered rigid vegetation Numerical modeling FLUENT Velocity distribution turbulent flow

Computational Simulation of turbulent flow Around Tractor-Trailers

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Fluid Dynamics & Materials Processing 2020年第1期16卷 91-103页

作者： D.O.Redchyts E.A.Shkvar S.V.Moiseienko Institute of Transport Systems and Technologies of Ukrainian National Academy of Science Dnipro49005Ukraine College of Engineering Zhejiang Normal UniversityJinhua321004China Kherson National Technical University Kherson73008Ukraine

A method to evaluate the properties of turbulent flow in proximity to the vehicle and close to the ground surface has been elaborated.Numerical simulations have been performed on the basis of the Unsteady Reynolds-averaged Navier-Stokes equations(URANS)written with respect to an arbitrary curvilinear coordinate system.These equations have been solved using the Spalart-Allmaras differential one-parametric turbulence model.The method of artificial compressibility has been used to improve the coupling of pressure and velocity in the framework of a finite volume approach.Time-averaged distributions of pressure fields,velocity components,streamlines in the entire area and near the tractor-trailer,as well as integral and distributed characteristic parameters(such as coefficients of pressure,friction and drag force)are presented.According to our results,the turbulent flow accelerates in the area of the tractor cabin and in the gap between surfaces.Above the driver’s cabin,a pressure drop occurs due to a sharp acceleration of flow in this area.Downstream,pressure is restored and becomes almost constant in proximity to the edge of the trailer.The dimensions of the separation area exceed the length of the transport system several times.Though agreement with experimental results is relatively limited due to the two-dimensional nature of the numerical simulations,the present approach succeeds in identifying the main physical effects involved in the considered dynamics.It might be used in future studies for initial approximate assessments of the influence of the vehicle shape on its aerodynamic characteristics.

关键词： High-speed vehicle tractor-trailer turbulent flow ground effect numerical modelling aerodynamic characteristics

Three-dimensional turbulent flow over cube-obstacles

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Chinese Physics B 2017年第1期26卷 278-284页

作者：卢浩赵文君张会强王兵王希麟 School of Aerospace Engineering Tsinghua University Faculty of Architecture The University of Hong Kong

In order to investigate the influence of surface roughness on turbulent flow and examine the wall-similarity hypothesis of Townsend, three-dimensional numerical study of turbulent channel flow over smooth and cube-rough walls with different roughness height has been carried out by using large eddy simulation（LES） coupled with immersed boundary method（IBM）. The effects of surface roughness array on mean and fluctuating velocity profiles, Reynolds shear stress, and typical coherent structures such as quasi-streamwise vortices（QSV） in turbulent channel flow are obtained. The significant influences on turbulent fluctuations and structures are observed in roughness sub-layer（five times of roughness height）.However, no dramatic modification of the log-law of the mean flow velocity and turbulence fluctuations can be found by surface cube roughness in the outer layer. Therefore, the results support the wall-similarity hypothesis. Moreover, the von Karman constant decreases with the increase of roughness height in the present simulation results. Besides, the larger size of QSV and more intense ejections are induced by the roughness elements, which is crucial for heat and mass transfer enhancement.

关键词： turbulent flow channel flow large-eddy simulations coherent structures

Interfacial instability of sand patterns induced by turbulent shear flow

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International Journal of Sediment Research 2021年第4期36卷 449-456页

作者： Sk Zeeshan Ali Subhasish Dey Department of Civil Engineering Indian Institute of Technology Hyderabad Department of Civil Engineering Indian Institute of Technology Kharagpur Department of Hydraulic Engineering State Key Laboratory of Hydro-Science and Engineering Tsinghua University

When a turbulent shear flow above a plane sand surface entrains sand grains, it generates a variety of sand patterns. Fluvial sand forms two major interfacial patterns: meso-scale dunes and antidunes, and large-scale bars. Measurements have evidenced that under erosive conditions, meso-scale patterns either change to or coexist with large-scale patterns. However, it remains elusive what exactly drives the switching of interfacial patterns and how the switching occurs. Here, we showdcombing a flow model with a grain transport model, allowing for both the surface and suspended sand fluxes dthat the switching of patterns emerges from the shear-driven complex feedback between grain transport and topographic perturbations. The switching predominantly depends on the magnitudes of the Rouse number and the grain size to undisturbed flow depth ratio. The model offers quantitative predictions of the maximum amplification of sand patterns and unveils a new attraction erepulsion phenomenon.

关键词： Instability Sand patterns turbulent flow Sediment transport

A robust compact least-squares reconstruction method for compressible turbulent flow simulations of complex configurations

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Chinese Journal of Aeronautics 2023年第12期36卷 113-138页

作者： Jia YAN Zhengyu NIU Xiaoquan YANG Jue DING Xiaolong TANG Peifeng WENG Shanghai Institute of Applied Mathematics and Mechanics Shanghai UniversityShanghai 200072China School of Mechanics and Engineering Science Shanghai UniversityShanghai 200072China Shanghai University of Electric Power Shanghai 200090China

For the second-order finite volume method,implicit schemes and reconstruction methods are two main algorithms which influence the robustness and efficiency of the numerical simulations of compressible turbulent flows.In this paper,a compact least-squares reconstruction method is proposed to calculate the gradients for the distribution of flow field variables approximation.The compactness of the new reconstruction method is reflected in the gradient calculation process.The geometries of the face-neighboring elements are no longer utilized,and the weighted average values at the centroid of the interfaces are used to calculate the gradients instead of the values at the centroid of the face-neighboring elements.Meanwhile,an exact Jacobian solving strategy is developed for implicit temporal discretization.The accurate processing of Jacobian matrix can extensively improve the invertibility of the Jacobian matrix and avoid introducing extra numerical errors.In addition,a modified Venkatakrishnan limiter is applied to deal with the shock which may appear in transonic flows and the applicability of the mentioned methods is enhanced further.The combination of the proposed methods makes the numerical simulations of turbulent flow converge rapidly and steadily with an adaptive increasing CFL number.The numerical results of several benchmarks indicate that the proposed methods perform well in terms of robustness,efficiency and accuracy,and have good application potential in turbulent flow simulations of complex configurations.

关键词： Compact least-squares reconstruction method Exact Jacobian matrix Finite volume method Implicit schemes turbulent flow

Simulation of buoyancy-induced turbulent flow from a hot horizontal jet

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Journal of Hydrodynamics 2014年第1期26卷 104-113页

作者： El-AMIN M.F. SUN Shuyu SALAM Amgad Computational Transport Phenomena Laboratory (CTPL) Division of Physical Sciences and EngineeringKing Abdullah University of Science and Technology

Experimental visualizations and numerical simulations of a horizontal hot water jet entering cold water into a rectangular storage tank are described. Three different temperature differences and their corresponding Reynolds numbers are considered. Both experimental visualization and numerical computations are carried out for the same flow and thermal conditions. The realizable k-e model is used for modeling the turbulent flow while the buoyancy is modeled using the Boussinesq approximation. Polynomial approximations of the water properties are used to compare with the Boussinesq approximation. Numerical solutions are obtained for unsteady flow while pressure, velocity, temperature and turbulence distributions inside the water tank as well as the Froude number are analyzed. The experimental visualizations are performed at intervals of five seconds for all different cases. The simulated results are compared with the visualized results, and both of them show the stratification phenomena and buoyancy force effects due to temperature difference and density variation. After certain times, depending on the case condition, the flow tends to reach a steady state.

关键词： turbulent flow realizablc k - e turbulence model heat transfer jet heat storage

Investigation of scale efect for the computation of turbulent flow around a circular cylinder

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Acta Mechanica Sinica 2013年第5期29卷 641-648页

作者： Lin Lin Yan-Ying Wang State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology

In order to investigate the scale effect of turbulent flow around a circular cylinder, two similarity numbers （criteria） based on turbulent kinetic and dissipation rates associ- ated with the fluctuation characteristics of turbulence wake are deduced by analyzing the Reynolds averaged NavierStokes equations （RANS）. The RNG k-s models and finite volume method are used to solve the governing equations and the second-order implicit time and upwind space discretization algorithms are used to discrete the governing equations. A numerical computation of flow parameters around a two-dimensional circular cylinder with Reynolds numbers ranging from 102 to l07 is accomplished and the result indicates that the fluctuation of turbulence flow along the center line in the wake of circular cylinder can never be changed with increasing Reynolds numbers when Re ≥ 3 × 10^6. This conclusion is useful for controlling the scale of numerical calculations and for applying model test data to engineering practice.

关键词： turbulent flow flow around circular cylinder Scale effect Dynamic similarity