To meet the requirements of fast and automatic computation of subsonic and transonic aerodynamics in aircraft conceptual design,a novel finite volume solver for full potential flows on adaptive Cartesian grids is deve...To meet the requirements of fast and automatic computation of subsonic and transonic aerodynamics in aircraft conceptual design,a novel finite volume solver for full potential flows on adaptive Cartesian grids is developed in this paper.Cartesian grids with geometric adaptation are firstly generated automatically with boundary cells processed by cell-cutting and cell-merging algorithms.The nonlinear full potential equation is discretized by a finite volume scheme on these Cartesian grids and iteratively solved in an implicit fashion with a generalized minimum residual（GMRES） algorithm.During computation,solution-based mesh adaptation is also applied so as to capture flow features more accurately.An improved ghost-cell method is proposed to implement the non-penetration wall boundary condition where the velocity-potential of a ghost cell is modified by an analytic method instead.According to the characteristics of the Cartesian grids,the Kutta condition is applied by specially computing the gradients on Kutta-faces without directly assigning the potential jump to cells adjacent wake faces,which can significantly improve the solution converging speed.The feasibility and accuracy of the proposed method are validated by several typical cases of sub/transonic flows around an ONERA M6 wing,a DLR-F4 wing-body,and an unconventional figuration of a blended wing body（BWB）.The validation cases demonstrate a fast convergence with fully automatic grid treatment and computation,and the results suggest its capacity in application for aircraft conceptual design.展开更多
对传统直角坐标网格进行改进,根据计算机图形学对与物面相交的正方形网格进行切割,使单元与物面贴体,并能根据流场的变化对网格区域进行局部加密。结合直角坐标网格与非结构网格的特点,编写了自适应直角坐标网格的生成程序,并发展了基...对传统直角坐标网格进行改进,根据计算机图形学对与物面相交的正方形网格进行切割,使单元与物面贴体,并能根据流场的变化对网格区域进行局部加密。结合直角坐标网格与非结构网格的特点,编写了自适应直角坐标网格的生成程序,并发展了基于切割单元直角坐标网格的直接模拟蒙特卡洛(Direct simulation Monte Carlo,DSMC)方法。同时通过当地模拟分子数、动态时间步长技术优化DSMC方法,提升计算效率。数值结果表明,本方法在计算过程中使搜索效率得到大大提升,同时也保证了物面网格单元的贴体性,提高了物面附近流场的计算精度,还易于实现网格自适应。展开更多
In the present paper, flow configurations of cavitating flow around a straight NACA0009 foil with a gap between the foil tip and sidewall are investigated numerically by large eddy simulation（LES） coupled with Zwart...In the present paper, flow configurations of cavitating flow around a straight NACA0009 foil with a gap between the foil tip and sidewall are investigated numerically by large eddy simulation（LES） coupled with Zwart-Gerber-Belamri（ZGB） cavitation model. A Cartesian cut-cell method is used for mesh generation, which is of good orthogonality and high quality. A good agreement is obtained between simulation and experiment. Two influencing factors on vorticity distributions, the interaction between different vortices and the occurrence of cavitation, are discussed in detail based on the numerical results. A series of ？-shaped loops are observed during the development of the induced vortex, which is a result of the instability of vortex pair. This finding may provide a new viewpoint to control the evolution of tip-leakage vortex（TLV） cavitation. Moreover, it is found that the dilatation term plays a much more important role in the evolution of TLV cavitation compared with that in sheet cavitation.展开更多
染色体免疫共沉淀测序(Chromatin immunoprecipitation followed by sequencing,ChIP-seq)是研究DNA-蛋白质互作的有力工具,被广泛用于RNA聚合酶、转录因子和组蛋白修饰等在基因组上的精确定位。近年来,在ChIP-seq技术的基础上,科学家...染色体免疫共沉淀测序(Chromatin immunoprecipitation followed by sequencing,ChIP-seq)是研究DNA-蛋白质互作的有力工具,被广泛用于RNA聚合酶、转录因子和组蛋白修饰等在基因组上的精确定位。近年来,在ChIP-seq技术的基础上,科学家提出了一系列研究DNA-蛋白质互作的技术方法,提高了测序分辨率,降低了实验成本,极大推动了表观基因组学的发展。本文综述了多种DNA-蛋白质互作研究技术的原理及其应用场景,介绍了在单细胞水平上研究DNA-蛋白质互作的实现方法,并展望其未来发展的方向。展开更多
染色体靶向切割和标签化(clevage under target and tagment,CUT&Tag)技术利用Tn5转座酶与Protein A/G的融合蛋白,引导Tn5酶至与靶蛋白结合的抗体附近,对靶蛋白结合的附近染色质区域进行切割,随后通过标签化处理对片段化染色质进行...染色体靶向切割和标签化(clevage under target and tagment,CUT&Tag)技术利用Tn5转座酶与Protein A/G的融合蛋白,引导Tn5酶至与靶蛋白结合的抗体附近,对靶蛋白结合的附近染色质区域进行切割,随后通过标签化处理对片段化染色质进行文库制备,并利用高通量测序技术获取特定位点或蛋白质结合位置的染色质信息。CUT&Tag技术在蛋白质和DNA相互作用的研究领域起到了重大作用,不仅可以了解组蛋白修饰发生的位置,而且可以明确转录因子结合的区域。相较于传统的染色质免疫沉淀高通量测序(chromatin immunoprecipitation-sequencing,ChIP-seq)技术,CUT&Tag技术具有信噪比高、可重复性好、实验周期短、细胞投入量低等优点,在早期胚胎发育、干细胞、肿瘤以及表观遗传学等研究领域体现出巨大优势。本文将针对CUT&Tag在代谢组织细胞(以小鼠原代胰岛细胞为例)的具体操作步骤进行描述,以提供一种研究代谢细胞的表观遗传学方法。展开更多
With the characteristic of the quadtree data structure, a new mesh generation method, which adopts square meshes to decompose a background domain and a cut cell approach to express arbitrary boundaries, is proposed to...With the characteristic of the quadtree data structure, a new mesh generation method, which adopts square meshes to decompose a background domain and a cut cell approach to express arbitrary boundaries, is proposed to keep the grids generated with a good orthogonality easily. The solution of N-S equations via finite volume method for this kind of unstructured meshes is derived. The mesh generator and N-S solver are implemented to study two benchmark cases, i.e. a lid driven flow within an inclined square and a natural convection heat transfer flow in a square duct with an inner hot circular face. The simulation results are in agreement with the benchmark values, verifying that the present methodology is valid and will be a strong tool for two-dimensional flow and heat transfer simulations, especially in the case of complex boundaries.展开更多
It is of great practical significance to study the development process of cut lily for regulating flowering and preservation.In this study,the developmental process of lily cut flower was explored from cellular,morpho...It is of great practical significance to study the development process of cut lily for regulating flowering and preservation.In this study,the developmental process of lily cut flower was explored from cellular,morphological,and physiological aspects.Froma morphological aspect,the tepal edge grows faster than the midrib.The midrib groove of the flowering stage is wider than that of bud stage.The fast-growing edge of the petals results in the midrib bending outward.Moreover,the rapid growth of the stamens and stigmas also contributes to bud cracking.From the cellular aspect,in the bud stage there were more wrinkles in the outer epidermal cell wall of the tepal than those in the inner epidermal cell wall,indicating that asymmetric structural differences exist from the beginning of lily development.From a physiological aspect,from the bud cracking stage to the senescence stage,a variety of substances in the tepal cells gradually decreased,including total nitrogen,total phosphorus,total potassium,total calcium,starch,soluble sugar,and soluble protein,but not malondialdehyde.These results indicate that the asymmetric growth caused by this structural difference is responsible for flowering.The wrinkles in the cell wall can be regarded as indicators of senescent cells and are caused by the degradation of the cell wall and the loss of intracellular turgor pressure.The differences in the epidermal cells between the inner and outer tepal indicated ultrastructural changes in the tepal cells.The bud and flowering stages are maintained by the tepals acting as a sink.After flowering,the tepals gradually change from a sink to a source organ.Senescence of the cut lily flowers was caused by the decomposition of intracellular compounds in the tepals and the remobilization of nutrients from the tepals to the developing organs.展开更多
A multiphase microscopic interference system is designed to measure the height of cell which is important to the research of collective cell migration in physiology and medicine. This sys- tem can quantitatively measu...A multiphase microscopic interference system is designed to measure the height of cell which is important to the research of collective cell migration in physiology and medicine. This sys- tem can quantitatively measure cell height across a living monolayer without knowing the refractive index of cells. For the interference pattern, because the phases are all wrapped between - π to π, it is necessary to get the real phase through phase unwrapping,a method to restore the wrapped phase data of the object by using numerical calculations. Three representative algorithms are selected to unwrap the interference pattern of ceils： branch-cut method, quality-guided method and network method. Although each of them can restore the phase, their performances are obviously different. We compare these methods and find that branch-cut method needs the smallest execution time and can obtain good unwrapped patterns when noises are not serious.展开更多
In this paper, a Cartesian grid method with cut cell has been developed to simulate mold filling of casting process. Cut cells at the cast-mold interface are generated on the Cartesian grid. With the boundary cut cell...In this paper, a Cartesian grid method with cut cell has been developed to simulate mold filling of casting process. Cut cells at the cast-mold interface are generated on the Cartesian grid. With the boundary cut cells, a special treatment is necessary. That is Cartesian grid method with cut cell. A simple shape was tested and the cut cell method was compared with the traditional one on Cartesian grids. And, a developed method was applied to the real casting product simulation. Cartesian grid system causes momentum loss and unsound fluid flow patterns because of inaccurate generation of meshes. These problems have been improved by using cut cell method.展开更多
For solving water entry problems, a numerical method is presented, which is a CFD method based on free surface capturing method and Cartesian cut cell mesh.In this approach, incompressible Euler equations for a variab...For solving water entry problems, a numerical method is presented, which is a CFD method based on free surface capturing method and Cartesian cut cell mesh.In this approach, incompressible Euler equations for a variable density fluid are numerically calculated by the finite volume method.Then artificial compressibility method, dual time-stepping technique and Roe's approximate Riemann solver are adopted in the numerical scheme.Finally, some application cases are designed to show the ability of the current method to cope with water entry problems in ocean engineering.展开更多
In the field of casting flow simulation, the application of body-fitted coordinate(BFC) has not been widely used due to the difficulty and low efficiency of grid generation, despite the availability of good quality an...In the field of casting flow simulation, the application of body-fitted coordinate(BFC) has not been widely used due to the difficulty and low efficiency of grid generation, despite the availability of good quality analysis results. Cartesian coordinates, on the other hand, have been used predominantly in casting process simulations because of their relatively easy and fast grid generation. However, Cartesian grid systems cannot obtain accurate results because they cannot express the geometries properly. In this study, Cut Cell method was applied to solve this problem. The three-dimensional incompressible viscous governing equation was analyzed using a function defined for the volume and area of the casting in the cutting cell. Using the Cut Cell method, accurate flow analysis results were also obtained in the Cartesian grid systems. The tests of simple shape and the applications of actual casting product have been tried with Cut Cell method.展开更多
This paper presents the optimization of 3D valveless diaphragm micropump for medical applications.The pump comprises an inlet and outlet diffuser connected to the main chamber equipped with a periodically moving diaph...This paper presents the optimization of 3D valveless diaphragm micropump for medical applications.The pump comprises an inlet and outlet diffuser connected to the main chamber equipped with a periodically moving diaphragm that generates the unsteady flow within the device.The optimization,which is related exclusively to the diaphragm motion,aims at maximizing the net flowrate and minimizing the backflow at the outlet diffuser.All CFD analyses are performed using an in-house cut-cell method,based on the finite volume approach,on a many-processor system.To reduce the optimization turn-around time,two optimization methods,a gradient-free evolutionary algorithm enhanced by surrogate evaluation models and a gradient-based(GB)method are synergistically used.To support the GB optimization,the continuous adjoint method that computes the gradient of the objectives with respect to the design variables has been developed and programmed.Using the hybrid optimization method,the Pareto front of non-dominated solutions,in the two-objective space,is computed.Finally,a couple of optimal solutions selected from the computed Pareto front are re-evaluated by considering uncertainties in the operating conditions;these are quantified using the polynomial chaos expansion method.展开更多
基金co-supported by the National Natural Science Foundation of China(No.11672133)the Fundamental Research Funds for the Central UniversitiesThe support from the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions
文摘To meet the requirements of fast and automatic computation of subsonic and transonic aerodynamics in aircraft conceptual design,a novel finite volume solver for full potential flows on adaptive Cartesian grids is developed in this paper.Cartesian grids with geometric adaptation are firstly generated automatically with boundary cells processed by cell-cutting and cell-merging algorithms.The nonlinear full potential equation is discretized by a finite volume scheme on these Cartesian grids and iteratively solved in an implicit fashion with a generalized minimum residual（GMRES） algorithm.During computation,solution-based mesh adaptation is also applied so as to capture flow features more accurately.An improved ghost-cell method is proposed to implement the non-penetration wall boundary condition where the velocity-potential of a ghost cell is modified by an analytic method instead.According to the characteristics of the Cartesian grids,the Kutta condition is applied by specially computing the gradients on Kutta-faces without directly assigning the potential jump to cells adjacent wake faces,which can significantly improve the solution converging speed.The feasibility and accuracy of the proposed method are validated by several typical cases of sub/transonic flows around an ONERA M6 wing,a DLR-F4 wing-body,and an unconventional figuration of a blended wing body（BWB）.The validation cases demonstrate a fast convergence with fully automatic grid treatment and computation,and the results suggest its capacity in application for aircraft conceptual design.
文摘对传统直角坐标网格进行改进,根据计算机图形学对与物面相交的正方形网格进行切割,使单元与物面贴体,并能根据流场的变化对网格区域进行局部加密。结合直角坐标网格与非结构网格的特点,编写了自适应直角坐标网格的生成程序,并发展了基于切割单元直角坐标网格的直接模拟蒙特卡洛(Direct simulation Monte Carlo,DSMC)方法。同时通过当地模拟分子数、动态时间步长技术优化DSMC方法,提升计算效率。数值结果表明,本方法在计算过程中使搜索效率得到大大提升,同时也保证了物面网格单元的贴体性,提高了物面附近流场的计算精度,还易于实现网格自适应。
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51576143,11772239 and 91752105)the Science and Technology on Water Jet Propulsion Laboratory(Grant No.61422230101162223002)
文摘In the present paper, flow configurations of cavitating flow around a straight NACA0009 foil with a gap between the foil tip and sidewall are investigated numerically by large eddy simulation（LES） coupled with Zwart-Gerber-Belamri（ZGB） cavitation model. A Cartesian cut-cell method is used for mesh generation, which is of good orthogonality and high quality. A good agreement is obtained between simulation and experiment. Two influencing factors on vorticity distributions, the interaction between different vortices and the occurrence of cavitation, are discussed in detail based on the numerical results. A series of ？-shaped loops are observed during the development of the induced vortex, which is a result of the instability of vortex pair. This finding may provide a new viewpoint to control the evolution of tip-leakage vortex（TLV） cavitation. Moreover, it is found that the dilatation term plays a much more important role in the evolution of TLV cavitation compared with that in sheet cavitation.
文摘染色体免疫共沉淀测序(Chromatin immunoprecipitation followed by sequencing,ChIP-seq)是研究DNA-蛋白质互作的有力工具,被广泛用于RNA聚合酶、转录因子和组蛋白修饰等在基因组上的精确定位。近年来,在ChIP-seq技术的基础上,科学家提出了一系列研究DNA-蛋白质互作的技术方法,提高了测序分辨率,降低了实验成本,极大推动了表观基因组学的发展。本文综述了多种DNA-蛋白质互作研究技术的原理及其应用场景,介绍了在单细胞水平上研究DNA-蛋白质互作的实现方法,并展望其未来发展的方向。
文摘染色体靶向切割和标签化(clevage under target and tagment,CUT&Tag)技术利用Tn5转座酶与Protein A/G的融合蛋白,引导Tn5酶至与靶蛋白结合的抗体附近,对靶蛋白结合的附近染色质区域进行切割,随后通过标签化处理对片段化染色质进行文库制备,并利用高通量测序技术获取特定位点或蛋白质结合位置的染色质信息。CUT&Tag技术在蛋白质和DNA相互作用的研究领域起到了重大作用,不仅可以了解组蛋白修饰发生的位置,而且可以明确转录因子结合的区域。相较于传统的染色质免疫沉淀高通量测序(chromatin immunoprecipitation-sequencing,ChIP-seq)技术,CUT&Tag技术具有信噪比高、可重复性好、实验周期短、细胞投入量低等优点,在早期胚胎发育、干细胞、肿瘤以及表观遗传学等研究领域体现出巨大优势。本文将针对CUT&Tag在代谢组织细胞(以小鼠原代胰岛细胞为例)的具体操作步骤进行描述,以提供一种研究代谢细胞的表观遗传学方法。
基金Supported by Japan Society for the Promotion of Science (Grant No.C20560175) the National Natural Science Foundation of China (Grant Nos.10872159 and 40675011)
文摘With the characteristic of the quadtree data structure, a new mesh generation method, which adopts square meshes to decompose a background domain and a cut cell approach to express arbitrary boundaries, is proposed to keep the grids generated with a good orthogonality easily. The solution of N-S equations via finite volume method for this kind of unstructured meshes is derived. The mesh generator and N-S solver are implemented to study two benchmark cases, i.e. a lid driven flow within an inclined square and a natural convection heat transfer flow in a square duct with an inner hot circular face. The simulation results are in agreement with the benchmark values, verifying that the present methodology is valid and will be a strong tool for two-dimensional flow and heat transfer simulations, especially in the case of complex boundaries.
基金the Construction Project of Organic Fertilizer Production Using Crop Straw(Grant No.2019-319)the Major Social Public Welfare Project of Guangdong Zhongshan city(Grant No.2017B1021)“Major projects+task list”Project of Science and Technology Special Fund of Zhongshan City in 2020(Grant No.2020sdr009).
文摘It is of great practical significance to study the development process of cut lily for regulating flowering and preservation.In this study,the developmental process of lily cut flower was explored from cellular,morphological,and physiological aspects.Froma morphological aspect,the tepal edge grows faster than the midrib.The midrib groove of the flowering stage is wider than that of bud stage.The fast-growing edge of the petals results in the midrib bending outward.Moreover,the rapid growth of the stamens and stigmas also contributes to bud cracking.From the cellular aspect,in the bud stage there were more wrinkles in the outer epidermal cell wall of the tepal than those in the inner epidermal cell wall,indicating that asymmetric structural differences exist from the beginning of lily development.From a physiological aspect,from the bud cracking stage to the senescence stage,a variety of substances in the tepal cells gradually decreased,including total nitrogen,total phosphorus,total potassium,total calcium,starch,soluble sugar,and soluble protein,but not malondialdehyde.These results indicate that the asymmetric growth caused by this structural difference is responsible for flowering.The wrinkles in the cell wall can be regarded as indicators of senescent cells and are caused by the degradation of the cell wall and the loss of intracellular turgor pressure.The differences in the epidermal cells between the inner and outer tepal indicated ultrastructural changes in the tepal cells.The bud and flowering stages are maintained by the tepals acting as a sink.After flowering,the tepals gradually change from a sink to a source organ.Senescence of the cut lily flowers was caused by the decomposition of intracellular compounds in the tepals and the remobilization of nutrients from the tepals to the developing organs.
基金Supported by the International Technology Cooperation Projects of BIT(GZ 20110451)
文摘A multiphase microscopic interference system is designed to measure the height of cell which is important to the research of collective cell migration in physiology and medicine. This sys- tem can quantitatively measure cell height across a living monolayer without knowing the refractive index of cells. For the interference pattern, because the phases are all wrapped between - π to π, it is necessary to get the real phase through phase unwrapping,a method to restore the wrapped phase data of the object by using numerical calculations. Three representative algorithms are selected to unwrap the interference pattern of ceils： branch-cut method, quality-guided method and network method. Although each of them can restore the phase, their performances are obviously different. We compare these methods and find that branch-cut method needs the smallest execution time and can obtain good unwrapped patterns when noises are not serious.
文摘In this paper, a Cartesian grid method with cut cell has been developed to simulate mold filling of casting process. Cut cells at the cast-mold interface are generated on the Cartesian grid. With the boundary cut cells, a special treatment is necessary. That is Cartesian grid method with cut cell. A simple shape was tested and the cut cell method was compared with the traditional one on Cartesian grids. And, a developed method was applied to the real casting product simulation. Cartesian grid system causes momentum loss and unsound fluid flow patterns because of inaccurate generation of meshes. These problems have been improved by using cut cell method.
基金Supported by the National 863 Plan Foundation under Grant No.2006AA09A104
文摘For solving water entry problems, a numerical method is presented, which is a CFD method based on free surface capturing method and Cartesian cut cell mesh.In this approach, incompressible Euler equations for a variable density fluid are numerically calculated by the finite volume method.Then artificial compressibility method, dual time-stepping technique and Roe's approximate Riemann solver are adopted in the numerical scheme.Finally, some application cases are designed to show the ability of the current method to cope with water entry problems in ocean engineering.
基金supported by the Ministry of Trade,Industry and Energy(MOTIE,Korea)(Project Name:Development of 500MPa URF&SIL 3 Manifold and Subsea System Engineering for Deepsea Field)
文摘In the field of casting flow simulation, the application of body-fitted coordinate(BFC) has not been widely used due to the difficulty and low efficiency of grid generation, despite the availability of good quality analysis results. Cartesian coordinates, on the other hand, have been used predominantly in casting process simulations because of their relatively easy and fast grid generation. However, Cartesian grid systems cannot obtain accurate results because they cannot express the geometries properly. In this study, Cut Cell method was applied to solve this problem. The three-dimensional incompressible viscous governing equation was analyzed using a function defined for the volume and area of the casting in the cutting cell. Using the Cut Cell method, accurate flow analysis results were also obtained in the Cartesian grid systems. The tests of simple shape and the applications of actual casting product have been tried with Cut Cell method.
文摘This paper presents the optimization of 3D valveless diaphragm micropump for medical applications.The pump comprises an inlet and outlet diffuser connected to the main chamber equipped with a periodically moving diaphragm that generates the unsteady flow within the device.The optimization,which is related exclusively to the diaphragm motion,aims at maximizing the net flowrate and minimizing the backflow at the outlet diffuser.All CFD analyses are performed using an in-house cut-cell method,based on the finite volume approach,on a many-processor system.To reduce the optimization turn-around time,two optimization methods,a gradient-free evolutionary algorithm enhanced by surrogate evaluation models and a gradient-based(GB)method are synergistically used.To support the GB optimization,the continuous adjoint method that computes the gradient of the objectives with respect to the design variables has been developed and programmed.Using the hybrid optimization method,the Pareto front of non-dominated solutions,in the two-objective space,is computed.Finally,a couple of optimal solutions selected from the computed Pareto front are re-evaluated by considering uncertainties in the operating conditions;these are quantified using the polynomial chaos expansion method.
