In the case of lid-driven deep cavity flow, the effects of different resolutions of local grid refinement have been studied in the frame of multiple relaxation times (MRT) lattice Boltzmann method (LBM). In all the ca...In the case of lid-driven deep cavity flow, the effects of different resolutions of local grid refinement have been studied in the frame of multiple relaxation times (MRT) lattice Boltzmann method (LBM). In all the cases, the aspect ratio and Reynolds number are set as 1.5 and 3.200, respectively. First, the applied method is validated by comparing it with two reported works, with which agreements are reached. Then, six separate degrees of local grid refinement at the upper left corner, i.e. purely coarse grid, including 1/64, 1/32, 1/16, 1/8, 1/4 refinements of the lattice number in the width direction have been studied in detail. The results give the following indications:① The refinement degrees lower than 1/8 produce similar results;② For single corner refinement, 1/4 refinement is adequate for clearing the noises in the singularity zone to a large extent;③ New noise around the interface between coarse and fine zones are introduced by local grid refinement. Finally, refinement of entire subzone neighboring the lid is examined to avoid introducing new noises and it has been found effective.展开更多
The concentration and velocity fields of two refractive index matched miscible shear-thinning fluids in a lid-driven cavity were investigated by using planar laser-induced fluorescence and particle image velocimetry,a...The concentration and velocity fields of two refractive index matched miscible shear-thinning fluids in a lid-driven cavity were investigated by using planar laser-induced fluorescence and particle image velocimetry,as well by computational fluid dynamics.Quantitative analyses show that the results obtained by flow simulations with the species transport model are in good agreement with the experimental results.The effects of different parameters were studied by using the intensity of segregation.For two fluids with the same rheological parameters,the relative amounts of liquids H_(1)/H and the power-law index n dominate the mixing process while the Reynolds number Re plays a marginal role.As for two fluids with density difference,buoyancy has significant influence on the mixing process.The dimensionless group Ar/Re(redefined such as to include shear thinning behavior)is proposed for assessing the effect of buoyancy and rheological properties on the mixing of miscible shear-thinning fluids.展开更多
By coupling the non-equilibrium extrapolation scheme for boundary condition with the multi-relaxation-time lattice Boltzmann method, this paper finds that the stability of the multi-relaxation-time model can be improv...By coupling the non-equilibrium extrapolation scheme for boundary condition with the multi-relaxation-time lattice Boltzmann method, this paper finds that the stability of the multi-relaxation-time model can be improved greatly, especially on simulating high Reynolds number (Re) flow. As a discovery, the super-stability analysed by Lallemand and Luo is verified and the complex structure of the cavity flow is also exhibited in our numerical simulation when Re is high enough. To the best knowledge of the authors, the maximum of Re which has been investigated by direct numerical simulation is only around 50 000 in the literature; however, this paper can readily extend the maximum to 1000 000 with the above combination.展开更多
To date, there are very few studies on the second Hopf bifurcation in a driven square cavity, although there are intensive investigations focused on the first Hopf bifurcation in literature, due to the difficulties of...To date, there are very few studies on the second Hopf bifurcation in a driven square cavity, although there are intensive investigations focused on the first Hopf bifurcation in literature, due to the difficulties of theoretical analyses and numerical simulations. In this paper, we study the characteristics of the second Hopf bifurcation in a driven square cavity by applying a consistent fourth-order compact finite difference scheme recently developed by us. We numerically identify the critical Reynolds number of the second Hopf bifurcation located in the interval of(11093.75, 11094.3604) by bisection. In addition, we find that there are two dominant frequencies in its spectral diagram when the flow is in the status of the second Hopf bifurcation, while only one dominant frequency is identified if the flow is in the first Hopf bifurcation via the Fourier analysis. More interestingly, the flow phase portrait of velocity components is found to make transition from a regular elliptical closed form for the first Hopf bifurcation to a non-elliptical closed form with self-intersection for the second Hopf bifurcation. Such characteristics disclose flow in a quasi-periodic state when the second Hopf bifurcation occurs.展开更多
To date,there are very few studies on the transition beyond second Hopf bifurcation in a lid-driven square cavity,due to the difficulties in theoretical analysis and numerical simulations.In this paper,we study the ch...To date,there are very few studies on the transition beyond second Hopf bifurcation in a lid-driven square cavity,due to the difficulties in theoretical analysis and numerical simulations.In this paper,we study the characteristics of the third Hopf bifurcation in a driven square cavity by applying a consistent fourth-order compact finite difference scheme rectently developed by us.We numerically identify the critical Reynolds number of the third Hopf bifurcation located in the interval of(13944.7021,13946.5333)by the method of bisection.Through Fourier analysis,it is discovered that the flow becomes chaotic with a characteristic of period-doubling bifurcation when the Reynolds number is beyond the third bifurcation critical interval.Nonlinear time series analysis further ascertains the flow chaotic behaviors via the phase diagram,Kolmogorov entropy and maximal Lyapunov exponent.The phase diagram changes interestingly from a closed curve with self-intersection to an unclosed curve and the attractor eventually becomes strange when the flow becomes chaotic.展开更多
A streamline upwind/Petrov-Galerkin (SUPG) finite element method based on a penalty function is pro- posed for steady incompressible Navier-Stokes equations. The SUPG stabilization technique is employed for the for-...A streamline upwind/Petrov-Galerkin (SUPG) finite element method based on a penalty function is pro- posed for steady incompressible Navier-Stokes equations. The SUPG stabilization technique is employed for the for- mulation of momentum equations. Using the penalty function method, the continuity equation is simplified and the pres- sure of the momentum equations is eliminated. The lid-driven cavity flow problem is solved using the present model. It is shown that steady flow simulations are computable up to Re = 27500, and the present results agree well with previous solutions. Tabulated results for the properties of the primary vortex are also provided for benchmarking purposes.展开更多
The investigation of supporting pressure is of great significance to the design of underground structures.Based on the kinematical approach of limit analysis,an improved failure mechanism is proposed,and the supportin...The investigation of supporting pressure is of great significance to the design of underground structures.Based on the kinematical approach of limit analysis,an improved failure mechanism is proposed,and the supporting pressure is investigated for deep buried cavity.Three failure mechanisms are first introduced according to the existing failure mechanisms of geotechnical structures of limit analysis.A comparison with respect to the optimal failure mechanisms and the upper bound solutions provided among these three mechanisms are then conducted in an attempt to obtain the improved failure mechanism.The results provided by the improved failure mechanism are in good agreement with those by the existing method,the numerical solution and field monitoring,which demonstrates that the proposed failure mechanism is effective for the upper bound analysis of supporting pressure.展开更多
Hydrodynamic mixed convection in a lid-driven hexagonal cavity with corner heater is numerically simulated in this paper by employing finite element method. The working fluid is assigned as air with a Prandtl num-ber ...Hydrodynamic mixed convection in a lid-driven hexagonal cavity with corner heater is numerically simulated in this paper by employing finite element method. The working fluid is assigned as air with a Prandtl num-ber of 0.71 throughout the simulation. The left and right walls of the hex-agonal cavity are kept thermally insulated and the lid moves top to bottom at a constant speed U0. The top left and right walls of the enclosure are maintained at cold temperature Tc. The bottom right wall is considered with a corner heater whereas the bottom remaining part is adiabatic and inside the cavity a square shape heated block Th. The focus of the work is to investigate the effect of Hartmann number, Richardson number, Grashof number and Reynolds number on the fluid flow and heat transfer characteristics inside the enclosure. A set of graphical results is presented in terms of streamlines, isotherms, local Nusselt number, velocity profiles, temperature profiles and average Nusselt numbers. The results reveal that heat transfer rate increases with increasing Richardson number and Hartmann number. It is also observed that, Hartmann number is a good control parameter for heat transfer in fluid flow in hexagonal cavity.展开更多
The strips U deep drawing experiments were carried out to study the effect of die cavity dimension with an extension machine manufactured by SANS company. The effects of parameters were analyzed in deep drawing proces...The strips U deep drawing experiments were carried out to study the effect of die cavity dimension with an extension machine manufactured by SANS company. The effects of parameters were analyzed in deep drawing process under different experimental conditions, such as punch load, reduction of thickness, angle of U part and surface quality. The experiment results show that the punch load increases with the decrease of female radius, and larger blank holder force enlarges the range of increasing. With the increasing of blank holder force, the angle of U part increases, and the reduction of foil thickness at the corner becomes larger. Obvious scratch and accumulation at the die cavity corner were observed by SEM. The investigation results indicate that micro U deep drawing of foil is affected by micro die cavity dimension.展开更多
This study aims to analyze mixed convection in a square cavity with two moving vertical walls by finite volume method.The cavity filled with Non-Newtonian fluid of Bingham model is heated from below and cooled by the ...This study aims to analyze mixed convection in a square cavity with two moving vertical walls by finite volume method.The cavity filled with Non-Newtonian fluid of Bingham model is heated from below and cooled by the other walls.This study has been conducted for certain parameters of Reynolds number(Re=1-100),Richardson number(Ri=1-20),Prandtl number(Pr=1-500),and Bingham number has been studied from 0 to 10.The results indicate that the increase in yield stress drops the heat transfer and the flow become flatter,while increasing Reynolds number augments it.The convective transport is dominant when increasing Richardson number which leads to enhance heat transfer in the cavity for both Newtonian and Non-Newtonian fluid.A correlation of Nusselt number is given in function of different parameters.展开更多
This paper investigates a polygonal finite element(PFE)to solve a two-dimensional(2D)incompressible steady fluid problem in a cavity square.It is a well-known standard benchmark(i.e.,lid-driven cavity flow)-to evaluat...This paper investigates a polygonal finite element(PFE)to solve a two-dimensional(2D)incompressible steady fluid problem in a cavity square.It is a well-known standard benchmark(i.e.,lid-driven cavity flow)-to evaluate the numerical methods in solving fluid problems controlled by the Navier-Stokes(N-S)equation system.The approximation solutions provided in this research are based on our developed equal-order mixed PFE,called Pe1Pe1.It is an exciting development based on constructing the mixed scheme method of two equal-order discretisation spaces for both fluid pressure and velocity fields of flows and our proposed stabilisation technique.In this research,to handle the nonlinear problem of N-S,the Picard iteration scheme is applied.Our proposed method’s performance and convergence are validated by several simulations coded by commercial software,i.e.,MATLAB.For this research,the benchmark is executed with variousReynolds numbers up to the maximum Re=1000.All results then numerously compared to available sources in the literature.展开更多
Steady,laminar mixed convection inside a lid-driven square cavity filled with nanofluid is investigated numerically.We consider the case where the right and left walls are moving downwards and upwards respectively an...Steady,laminar mixed convection inside a lid-driven square cavity filled with nanofluid is investigated numerically.We consider the case where the right and left walls are moving downwards and upwards respectively and maintained at different temperatures while the other two horizontal ones are kept adiabatic and impermeable.The set of nonlinear coupled governing mass,momentum,and energy equations are solved using an extensively validated and a highly accurate finite difference method of fourth-order.Comparisons with previously conducted investigations on special configurations are performed and show an excellent agreement.Meanwhile,attention is focused on the heat transfer enhancement when different nano-particles:Cu,Ag,Al2O3,TiO2 and Fe3O4 are incorporated separately in different base fluids such as:Water,Ethylene-glycol,Methanol and Kerosene oil.In this framework,the numerical results related to several mixtures are presented and concern flow pattern and heat transfer curves for various values of Richardson number[Ri=0.1,1 and 10].It turns out that the choice of the efficient binary mixture for an optimal heat transfer depends not only on the thermophysical properties of the nanofluids but also on the range of the Richardson number.Special attention is devoted to shedding light on the effect of the shape of the nanoparticles on the heat transfer in the case of Water-Ag nanofluid.It is concluded that the spherical shape is more suitable for a better heat transfer enhancement in comparison to the cylindrical ones.展开更多
An investigation on flow and heat transfer due to mixed convection, in a lid-driven rectangular cavity filled with Cu- water nanofluids and submitted to uniform heat flux along with its vertical short sides, has been ...An investigation on flow and heat transfer due to mixed convection, in a lid-driven rectangular cavity filled with Cu- water nanofluids and submitted to uniform heat flux along with its vertical short sides, has been conducted numerically by solving the full governing equations with the finite volume method and the SIMPLER algorithm. In the case of a slender enclosure, these equations are considerably reduced by using the parallel flow concept. Solutions, for the flow and temperature fields, and the heat transfer rate, have been obtained depending on the governing parameters, which are the Reynolds, the Richardson numbers and the solid volume fraction of nanoparticles. A perfect agreement has been found between the results of the two approaches for a wide range of the abovementioned parameters. It has been shown that at low and high Richardson numbers, the convection is ensured by lid and buoyancy-driven effects, respectively, whereas between these extremes, both mechanisms compete. Moreover, the addition of Cu-nanoparticles, into the pure water, has been seen enhancing and degrading heat transfer by lid and buoyancy-driven effects, respectively.展开更多
隧道衬砌内部空洞等病害检测已经成为隧道检修人员的主要工作之一。本文提出一种将探地雷达与深度学习相结合的隧道衬砌空洞检测方法,通过雷达探测和仿真模拟,得到大量衬砌雷达图像,并对图像进行标注和制作数据集。基于YOLOv5(You Only ...隧道衬砌内部空洞等病害检测已经成为隧道检修人员的主要工作之一。本文提出一种将探地雷达与深度学习相结合的隧道衬砌空洞检测方法,通过雷达探测和仿真模拟,得到大量衬砌雷达图像,并对图像进行标注和制作数据集。基于YOLOv5(You Only Look Once version 5)目标检测模型,结合数据集目标特征,提出一种检测衬砌空洞的算法,引入特征融合模块提高网络感受野,并采用K-means聚类算法提高检测准确率。通过现场检测,本文的检测方法准确率达到了97.7%,准确可靠,可在工程中进行应用。展开更多
Nanofluids have enjoyed a widespread use in many technological applications due to their peculiar properties.Numerical simulations are presented about the unsteady behavior of mixed convection of Fe_(3)O_(4)-water,Fe_...Nanofluids have enjoyed a widespread use in many technological applications due to their peculiar properties.Numerical simulations are presented about the unsteady behavior of mixed convection of Fe_(3)O_(4)-water,Fe_(3)O_(4)-kerosene,Fe_(3)O_(4)-ethylene glycol,and Fe_(3)O_(4)-engine oil nanofluids inside a lid-driven triangular cavity.In particular,a two-component non-homogeneous nanofluid model is used.The bottom wall of the enclosure is insulated,whereas the inclined wall is kept a constant(cold)temperature and various temperature laws are assumed for the vertical wall,namely:θ=1(Case 1),θ=Yð1YÞ(Case 2),andθ=sinð2-YÞ(Case 3).A tilted magnetic field of uniform strength is also present in the fluid domain.From a numerical point of view,the problem is addressed using the Galerkin weighted residual finite element method.The role played by different parameters is assessed,discussed critically and interpreted from a physical standpoint.We find that a higher aspect ratio can produce an increase in the average Nusselt number.Moreover,the Fe_(3)O_(4)-EO and Fe_(3)O_(4)-H2O nanofluids provide the highest and smallest rate of heat transfer,respectively,for all the considered(three variants of)thermal boundary conditions.展开更多
Mixed convection flow is one of the essential criteria of fluid flow and heat transfer. And its application has been increased due to modernization of society. So, to compete with the global world an analysis has been...Mixed convection flow is one of the essential criteria of fluid flow and heat transfer. And its application has been increased due to modernization of society. So, to compete with the global world an analysis has been investigated numerically. In this study we have considered 2D double lid driven cavity with two-sided adiabatic walls. This problem is illustrated mathematically by a collection of governing equations and the developed model has been solved numerically by using Finite Difference Method (FDM). The goal of the present study is to analyze numerically the thermal behaviour and parameters effect on heat transfer inside the 2D chamber. Also this analysis has been observed for the case where the upper wall is moving at positive direction and lower wall is moving at negative direction with constant speed. Furthermore, we have tried to analyze the velocity and temperature profiles for a vast range of dimensionless parameters namely Reynolds number (Re), Richardson number (Ri)?and Prandtl number?(Pr)?and presented graphically. Moreover, it is found that these flow parameters have significant effects in controlling the flow behavior inside the cavity. A comparison has been done to validate our code and found a good agreement. Finally, average Nusselt number (Nu)?has been studied for the effects of these parameters and presented in tabular form.展开更多
基金Supported by Science and Technology Development Planning of Shandong Province,P.R.China(2016GGX104018)
文摘In the case of lid-driven deep cavity flow, the effects of different resolutions of local grid refinement have been studied in the frame of multiple relaxation times (MRT) lattice Boltzmann method (LBM). In all the cases, the aspect ratio and Reynolds number are set as 1.5 and 3.200, respectively. First, the applied method is validated by comparing it with two reported works, with which agreements are reached. Then, six separate degrees of local grid refinement at the upper left corner, i.e. purely coarse grid, including 1/64, 1/32, 1/16, 1/8, 1/4 refinements of the lattice number in the width direction have been studied in detail. The results give the following indications:① The refinement degrees lower than 1/8 produce similar results;② For single corner refinement, 1/4 refinement is adequate for clearing the noises in the singularity zone to a large extent;③ New noise around the interface between coarse and fine zones are introduced by local grid refinement. Finally, refinement of entire subzone neighboring the lid is examined to avoid introducing new noises and it has been found effective.
基金The financial supports from the National Natural Science Foundation of China(22178014)。
文摘The concentration and velocity fields of two refractive index matched miscible shear-thinning fluids in a lid-driven cavity were investigated by using planar laser-induced fluorescence and particle image velocimetry,as well by computational fluid dynamics.Quantitative analyses show that the results obtained by flow simulations with the species transport model are in good agreement with the experimental results.The effects of different parameters were studied by using the intensity of segregation.For two fluids with the same rheological parameters,the relative amounts of liquids H_(1)/H and the power-law index n dominate the mixing process while the Reynolds number Re plays a marginal role.As for two fluids with density difference,buoyancy has significant influence on the mixing process.The dimensionless group Ar/Re(redefined such as to include shear thinning behavior)is proposed for assessing the effect of buoyancy and rheological properties on the mixing of miscible shear-thinning fluids.
基金Project supported by the National Natural Science Foundation of China (Grant No 70271069).
文摘By coupling the non-equilibrium extrapolation scheme for boundary condition with the multi-relaxation-time lattice Boltzmann method, this paper finds that the stability of the multi-relaxation-time model can be improved greatly, especially on simulating high Reynolds number (Re) flow. As a discovery, the super-stability analysed by Lallemand and Luo is verified and the complex structure of the cavity flow is also exhibited in our numerical simulation when Re is high enough. To the best knowledge of the authors, the maximum of Re which has been investigated by direct numerical simulation is only around 50 000 in the literature; however, this paper can readily extend the maximum to 1000 000 with the above combination.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11601013 and 91530325)。
文摘To date, there are very few studies on the second Hopf bifurcation in a driven square cavity, although there are intensive investigations focused on the first Hopf bifurcation in literature, due to the difficulties of theoretical analyses and numerical simulations. In this paper, we study the characteristics of the second Hopf bifurcation in a driven square cavity by applying a consistent fourth-order compact finite difference scheme recently developed by us. We numerically identify the critical Reynolds number of the second Hopf bifurcation located in the interval of(11093.75, 11094.3604) by bisection. In addition, we find that there are two dominant frequencies in its spectral diagram when the flow is in the status of the second Hopf bifurcation, while only one dominant frequency is identified if the flow is in the first Hopf bifurcation via the Fourier analysis. More interestingly, the flow phase portrait of velocity components is found to make transition from a regular elliptical closed form for the first Hopf bifurcation to a non-elliptical closed form with self-intersection for the second Hopf bifurcation. Such characteristics disclose flow in a quasi-periodic state when the second Hopf bifurcation occurs.
基金Project supported by the National Natural Science Foundation of China(Grant No.12162001)the Natural Science Foundation of Ningxia(Grant No.2019AAC03129)the Construction Project of First-Class Disciplines in Ningxia Higher Education(Grant No.NXYLXK2017B09)。
文摘To date,there are very few studies on the transition beyond second Hopf bifurcation in a lid-driven square cavity,due to the difficulties in theoretical analysis and numerical simulations.In this paper,we study the characteristics of the third Hopf bifurcation in a driven square cavity by applying a consistent fourth-order compact finite difference scheme rectently developed by us.We numerically identify the critical Reynolds number of the third Hopf bifurcation located in the interval of(13944.7021,13946.5333)by the method of bisection.Through Fourier analysis,it is discovered that the flow becomes chaotic with a characteristic of period-doubling bifurcation when the Reynolds number is beyond the third bifurcation critical interval.Nonlinear time series analysis further ascertains the flow chaotic behaviors via the phase diagram,Kolmogorov entropy and maximal Lyapunov exponent.The phase diagram changes interestingly from a closed curve with self-intersection to an unclosed curve and the attractor eventually becomes strange when the flow becomes chaotic.
基金the National Natural Science Foundation of China (Grants 41372301 and 51349011)the Preeminent Youth Talent Project of Southwest University of Science and Technology (Grant 13zx9109)
文摘A streamline upwind/Petrov-Galerkin (SUPG) finite element method based on a penalty function is pro- posed for steady incompressible Navier-Stokes equations. The SUPG stabilization technique is employed for the for- mulation of momentum equations. Using the penalty function method, the continuity equation is simplified and the pres- sure of the momentum equations is eliminated. The lid-driven cavity flow problem is solved using the present model. It is shown that steady flow simulations are computable up to Re = 27500, and the present results agree well with previous solutions. Tabulated results for the properties of the primary vortex are also provided for benchmarking purposes.
基金Project(51674115)supported by the National Natural Science Foundation of ChinaProject(51434006)supported by the Key Program of the National Natural Science Foundation of ChinaProject(2015JJ4024)supported by the Natural Science Foundation of Hunan Province,China
文摘The investigation of supporting pressure is of great significance to the design of underground structures.Based on the kinematical approach of limit analysis,an improved failure mechanism is proposed,and the supporting pressure is investigated for deep buried cavity.Three failure mechanisms are first introduced according to the existing failure mechanisms of geotechnical structures of limit analysis.A comparison with respect to the optimal failure mechanisms and the upper bound solutions provided among these three mechanisms are then conducted in an attempt to obtain the improved failure mechanism.The results provided by the improved failure mechanism are in good agreement with those by the existing method,the numerical solution and field monitoring,which demonstrates that the proposed failure mechanism is effective for the upper bound analysis of supporting pressure.
文摘Hydrodynamic mixed convection in a lid-driven hexagonal cavity with corner heater is numerically simulated in this paper by employing finite element method. The working fluid is assigned as air with a Prandtl num-ber of 0.71 throughout the simulation. The left and right walls of the hex-agonal cavity are kept thermally insulated and the lid moves top to bottom at a constant speed U0. The top left and right walls of the enclosure are maintained at cold temperature Tc. The bottom right wall is considered with a corner heater whereas the bottom remaining part is adiabatic and inside the cavity a square shape heated block Th. The focus of the work is to investigate the effect of Hartmann number, Richardson number, Grashof number and Reynolds number on the fluid flow and heat transfer characteristics inside the enclosure. A set of graphical results is presented in terms of streamlines, isotherms, local Nusselt number, velocity profiles, temperature profiles and average Nusselt numbers. The results reveal that heat transfer rate increases with increasing Richardson number and Hartmann number. It is also observed that, Hartmann number is a good control parameter for heat transfer in fluid flow in hexagonal cavity.
基金Projects(50835002 50805035) supported by the National Natural Science Foundation of ChinaProject(2008RFQXG041) supported by the Foundation for Innovation Scholars of Harbin, China
文摘The strips U deep drawing experiments were carried out to study the effect of die cavity dimension with an extension machine manufactured by SANS company. The effects of parameters were analyzed in deep drawing process under different experimental conditions, such as punch load, reduction of thickness, angle of U part and surface quality. The experiment results show that the punch load increases with the decrease of female radius, and larger blank holder force enlarges the range of increasing. With the increasing of blank holder force, the angle of U part increases, and the reduction of foil thickness at the corner becomes larger. Obvious scratch and accumulation at the die cavity corner were observed by SEM. The investigation results indicate that micro U deep drawing of foil is affected by micro die cavity dimension.
文摘This study aims to analyze mixed convection in a square cavity with two moving vertical walls by finite volume method.The cavity filled with Non-Newtonian fluid of Bingham model is heated from below and cooled by the other walls.This study has been conducted for certain parameters of Reynolds number(Re=1-100),Richardson number(Ri=1-20),Prandtl number(Pr=1-500),and Bingham number has been studied from 0 to 10.The results indicate that the increase in yield stress drops the heat transfer and the flow become flatter,while increasing Reynolds number augments it.The convective transport is dominant when increasing Richardson number which leads to enhance heat transfer in the cavity for both Newtonian and Non-Newtonian fluid.A correlation of Nusselt number is given in function of different parameters.
基金This work was supported by the VLIR-UOS TEAM Project,VN2017TEA454A 103,‘An innovative solution to protect Vietnamese coastal riverbanks from floods and erosion’funded by the Flemish Government.
文摘This paper investigates a polygonal finite element(PFE)to solve a two-dimensional(2D)incompressible steady fluid problem in a cavity square.It is a well-known standard benchmark(i.e.,lid-driven cavity flow)-to evaluate the numerical methods in solving fluid problems controlled by the Navier-Stokes(N-S)equation system.The approximation solutions provided in this research are based on our developed equal-order mixed PFE,called Pe1Pe1.It is an exciting development based on constructing the mixed scheme method of two equal-order discretisation spaces for both fluid pressure and velocity fields of flows and our proposed stabilisation technique.In this research,to handle the nonlinear problem of N-S,the Picard iteration scheme is applied.Our proposed method’s performance and convergence are validated by several simulations coded by commercial software,i.e.,MATLAB.For this research,the benchmark is executed with variousReynolds numbers up to the maximum Re=1000.All results then numerously compared to available sources in the literature.
文摘Steady,laminar mixed convection inside a lid-driven square cavity filled with nanofluid is investigated numerically.We consider the case where the right and left walls are moving downwards and upwards respectively and maintained at different temperatures while the other two horizontal ones are kept adiabatic and impermeable.The set of nonlinear coupled governing mass,momentum,and energy equations are solved using an extensively validated and a highly accurate finite difference method of fourth-order.Comparisons with previously conducted investigations on special configurations are performed and show an excellent agreement.Meanwhile,attention is focused on the heat transfer enhancement when different nano-particles:Cu,Ag,Al2O3,TiO2 and Fe3O4 are incorporated separately in different base fluids such as:Water,Ethylene-glycol,Methanol and Kerosene oil.In this framework,the numerical results related to several mixtures are presented and concern flow pattern and heat transfer curves for various values of Richardson number[Ri=0.1,1 and 10].It turns out that the choice of the efficient binary mixture for an optimal heat transfer depends not only on the thermophysical properties of the nanofluids but also on the range of the Richardson number.Special attention is devoted to shedding light on the effect of the shape of the nanoparticles on the heat transfer in the case of Water-Ag nanofluid.It is concluded that the spherical shape is more suitable for a better heat transfer enhancement in comparison to the cylindrical ones.
文摘An investigation on flow and heat transfer due to mixed convection, in a lid-driven rectangular cavity filled with Cu- water nanofluids and submitted to uniform heat flux along with its vertical short sides, has been conducted numerically by solving the full governing equations with the finite volume method and the SIMPLER algorithm. In the case of a slender enclosure, these equations are considerably reduced by using the parallel flow concept. Solutions, for the flow and temperature fields, and the heat transfer rate, have been obtained depending on the governing parameters, which are the Reynolds, the Richardson numbers and the solid volume fraction of nanoparticles. A perfect agreement has been found between the results of the two approaches for a wide range of the abovementioned parameters. It has been shown that at low and high Richardson numbers, the convection is ensured by lid and buoyancy-driven effects, respectively, whereas between these extremes, both mechanisms compete. Moreover, the addition of Cu-nanoparticles, into the pure water, has been seen enhancing and degrading heat transfer by lid and buoyancy-driven effects, respectively.
文摘隧道衬砌内部空洞等病害检测已经成为隧道检修人员的主要工作之一。本文提出一种将探地雷达与深度学习相结合的隧道衬砌空洞检测方法,通过雷达探测和仿真模拟,得到大量衬砌雷达图像,并对图像进行标注和制作数据集。基于YOLOv5(You Only Look Once version 5)目标检测模型,结合数据集目标特征,提出一种检测衬砌空洞的算法,引入特征融合模块提高网络感受野,并采用K-means聚类算法提高检测准确率。通过现场检测,本文的检测方法准确率达到了97.7%,准确可靠,可在工程中进行应用。
文摘Nanofluids have enjoyed a widespread use in many technological applications due to their peculiar properties.Numerical simulations are presented about the unsteady behavior of mixed convection of Fe_(3)O_(4)-water,Fe_(3)O_(4)-kerosene,Fe_(3)O_(4)-ethylene glycol,and Fe_(3)O_(4)-engine oil nanofluids inside a lid-driven triangular cavity.In particular,a two-component non-homogeneous nanofluid model is used.The bottom wall of the enclosure is insulated,whereas the inclined wall is kept a constant(cold)temperature and various temperature laws are assumed for the vertical wall,namely:θ=1(Case 1),θ=Yð1YÞ(Case 2),andθ=sinð2-YÞ(Case 3).A tilted magnetic field of uniform strength is also present in the fluid domain.From a numerical point of view,the problem is addressed using the Galerkin weighted residual finite element method.The role played by different parameters is assessed,discussed critically and interpreted from a physical standpoint.We find that a higher aspect ratio can produce an increase in the average Nusselt number.Moreover,the Fe_(3)O_(4)-EO and Fe_(3)O_(4)-H2O nanofluids provide the highest and smallest rate of heat transfer,respectively,for all the considered(three variants of)thermal boundary conditions.
文摘Mixed convection flow is one of the essential criteria of fluid flow and heat transfer. And its application has been increased due to modernization of society. So, to compete with the global world an analysis has been investigated numerically. In this study we have considered 2D double lid driven cavity with two-sided adiabatic walls. This problem is illustrated mathematically by a collection of governing equations and the developed model has been solved numerically by using Finite Difference Method (FDM). The goal of the present study is to analyze numerically the thermal behaviour and parameters effect on heat transfer inside the 2D chamber. Also this analysis has been observed for the case where the upper wall is moving at positive direction and lower wall is moving at negative direction with constant speed. Furthermore, we have tried to analyze the velocity and temperature profiles for a vast range of dimensionless parameters namely Reynolds number (Re), Richardson number (Ri)?and Prandtl number?(Pr)?and presented graphically. Moreover, it is found that these flow parameters have significant effects in controlling the flow behavior inside the cavity. A comparison has been done to validate our code and found a good agreement. Finally, average Nusselt number (Nu)?has been studied for the effects of these parameters and presented in tabular form.