基于有限体积三维水动力海洋数值模型FVCOM(Finite-Volume Community Ocean Model)对库克海峡邻近海域的潮汐潮流进行了数值模拟分析,同时搜集了验潮站的潮位数据及其潮汐调和分析数据,对模型结果进行了对比验证。结果表明,库克海峡两...基于有限体积三维水动力海洋数值模型FVCOM(Finite-Volume Community Ocean Model)对库克海峡邻近海域的潮汐潮流进行了数值模拟分析,同时搜集了验潮站的潮位数据及其潮汐调和分析数据,对模型结果进行了对比验证。结果表明,库克海峡两侧潮汐存在着显著差异,北侧由新西兰海岸向塔斯曼海的方向上,振幅逐渐降低,南侧由南部宽阔海域向新西兰南部岸线的方向上,振幅逐渐升高,且该区域的潮汐过程受地形和岸线影响较大。库克海峡中部存在典型的往复流,且以向南流动为主。库克海峡南侧存在的隆起地形和海沟是海峡之外该海域潮汐过程的重要影响因子,具体表现在南部海洋中隆起区域的潮流流速显著增加,流向也随之改变。与实测资料的对比结果表明,本研究的数值模拟结果与实测资料基本吻合,能够准确地模拟库克海峡邻近海域的潮汐潮流状况,为相关海洋工程建设以及科学研究等提供了重要的试验依据。展开更多
We construct an unconventional divergence preserving discretization of updated Lagrangian ideal magnetohydrodynamics(MHD)over simplicial grids.The cell-centered finite-volume(FV)method employed to discretize the conse...We construct an unconventional divergence preserving discretization of updated Lagrangian ideal magnetohydrodynamics(MHD)over simplicial grids.The cell-centered finite-volume(FV)method employed to discretize the conservation laws of volume,momentum,and total energy is rigorously the same as the one developed to simulate hyperelasticity equations.By construction this moving mesh method ensures the compatibility between the mesh displacement and the approximation of the volume flux by means of the nodal velocity and the attached unit corner normal vector which is nothing but the partial derivative of the cell volume with respect to the node coordinate under consideration.This is precisely the definition of the compatibility with the Geometrical Conservation Law which is the cornerstone of any proper multi-dimensional moving mesh FV discretization.The momentum and the total energy fluxes are approximated utilizing the partition of cell faces into sub-faces and the concept of sub-face force which is the traction force attached to each sub-face impinging at a node.We observe that the time evolution of the magnetic field might be simply expressed in terms of the deformation gradient which characterizes the Lagrange-to-Euler mapping.In this framework,the divergence of the magnetic field is conserved with respect to time thanks to the Piola formula.Therefore,we solve the fully compatible updated Lagrangian discretization of the deformation gradient tensor for updating in a simple manner the cell-centered value of the magnetic field.Finally,the sub-face traction force is expressed in terms of the nodal velocity to ensure a semi-discrete entropy inequality within each cell.The conservation of momentum and total energy is recovered prescribing the balance of all the sub-face forces attached to the sub-faces impinging at a given node.This balance corresponds to a vectorial system satisfied by the nodal velocity.It always admits a unique solution which provides the nodal velocity.The robustness and the accuracy of this unconventional FV scheme have been demonstrated by employing various representative test cases.Finally,it is worth emphasizing that once you have an updated Lagrangian code for solving hyperelasticity you also get an almost free updated Lagrangian code for solving ideal MHD ensuring exactly the compatibility with the involution constraint for the magnetic field at the discrete level.展开更多
基于FVCOM(Finite-Volu me Coastal Ocean Model)三维水动力模型,将整个渤海海域及其邻近的黄海北部海域作为研究海域,以8个主要分潮(M_(2),S_(2),K_(2),N_(2),K_(1),O_(1),P_(1),Q_(1))调和分析得到的水位驱动开边界,对研究海域的潮汐...基于FVCOM(Finite-Volu me Coastal Ocean Model)三维水动力模型,将整个渤海海域及其邻近的黄海北部海域作为研究海域,以8个主要分潮(M_(2),S_(2),K_(2),N_(2),K_(1),O_(1),P_(1),Q_(1))调和分析得到的水位驱动开边界,对研究海域的潮汐、潮流进行了数值模拟。文章通过对模拟结果中的水位数据和流场数据进行调和分析,绘制了研究海域的四大主要分潮(M_(2),S_(2),K_(1),O_(1))的同潮时图、潮流椭圆分布图,分析判断了研究海域的潮汐、潮流类型。经过对比分析,与公认的结果非常一致,说明了FVCOM模型能够很好地模拟近海的潮汐潮流。展开更多
In this study,the cylindrical finite-volume method(FVM)is advanced for the efficient and high-precision simulation of the logging while drilling(LWD)orthogonal azimuth electromagnetic tool(OAEMT)response in a three-di...In this study,the cylindrical finite-volume method(FVM)is advanced for the efficient and high-precision simulation of the logging while drilling(LWD)orthogonal azimuth electromagnetic tool(OAEMT)response in a three-dimensional(3 D)anisotropic formation.To overcome the ill-condition and convergence problems arising from the low induction number,Maxwell’s equations are reformulated into a mixed Helmholtz equation for the coupled potentials in a cylindrical coordinate system.The electrical fi eld continuation method is applied to approximate the perfectly electrical conducting(PEC)boundary condition,to improve the discretization accuracy of the Helmholtz equation on the surface of metal mandrels.On the base,the 3 D FVM on Lebedev’s staggered grids in the cylindrical coordinates is employed to discretize the mixed equations to ensure good conformity with typical well-logging tool geometries.The equivalent conductivity in a non-uniform element is determined by a standardization technique.The direct solver,PARDISO,is applied to efficiently solve the sparse linear equation systems for the multi-transmitter problem.To reduce the number of calls to PARDISO,the whole computational domain is divided into small windows that contain multiple measuring points.The electromagnetic(EM)solutions produced by all the transmitters per window are simultaneously solved because the discrete matrix,relevant to all the transmitters in the same window,is changed.Finally,the 3 D FVM is validated against the numerical mode matching method(NMM),and the characteristics of both the coaxial and coplanar responses of the EM field tool are investigated using the numerical results.展开更多
A finite-volume charge method has been proposed to simulate PIN diodes and insulated-gate bipolar transistor(IGBT)devices using SPICE simulators by extending the lumped-charge method.The new method assumes local quasi...A finite-volume charge method has been proposed to simulate PIN diodes and insulated-gate bipolar transistor(IGBT)devices using SPICE simulators by extending the lumped-charge method.The new method assumes local quasi-neutrality in the undepleted N^(-)base region and uses the total collector current,the nodal hole density and voltage as the basic quantities.In SPICE implementation,it makes clear and accurate definitions of three kinds of nodes—the carrier density nodes,the voltage nodes and the current generator nodes—in the undepleted N^(-)base region.It uses central finite difference to approximate electron and hole current generators and sets up the current continuity equation in a control volume for every carrier density node in the undepleted N^(-)base region.It is easy to increase the number of nodes to describe the fast spatially varying carrier density in transient processes.We use this method to simulate IGBT devices in SPICE simulators and get a good agreement with technology computer-aided design simulations.展开更多
In this paper, a stochastic finite-volume solver based on polynomial chaos expansion is developed. The upwind scheme is used to avoid the numerical instabilities. The Burgers’ equation subjected to deterministic boun...In this paper, a stochastic finite-volume solver based on polynomial chaos expansion is developed. The upwind scheme is used to avoid the numerical instabilities. The Burgers’ equation subjected to deterministic boundary conditions and random viscosity is solved. The solution uncertainty is quantified for different values of viscosity. Monte-Carlo simulations are used to validate and compare the developed solver. The mean, standard deviation and the probability distribution function (p.d.f) of the stochastic Burgers’ solution is quantified and the effect of some parameters is investigated. The large sparse linear system resulting from the stochastic solver is solved in parallel to enhance the performance. Also, Monte-Carlo simulations are done in parallel and the execution times are compared in both cases.展开更多
文摘基于响应系数的数值模拟是在港湾环境容量评估中的常用方法之一,但目前常见的海洋模型中没有可同时计算多个释放点的响应系数场且互不干扰的示踪物模块。针对响应系数法的特点,本研究对三维水动力海洋数值模型FVCOM(Finite-Volume Community Ocean Model)的示踪物模块(dyeing tracking,DYE)进行改进,在模型原有DYE模块的基础上增加多个功能与原DYE模块相同的独立模块,即并行计算多个DYE模块,使FVCOM能够同时计算多个互不干扰的保守示踪物模块。以一个理想地形矩形案例和一个象山港理想地形案例进行了测试。结果显示,改进算法模拟的多点源示踪物平流扩散过程互不影响,且模拟的响应系数场与传统算法一致;相较于传统算法,改进算法的计算过程耗时更短,对理想矩形案例的计算效率最高提升了85%,对象山港案例最高提升了78%;在并行运算的条件下,改进算法对CPU进程的利用率更高。使用改进后的DYE计算响应系数场可以缩短海洋环境容量评估的整体用时。
文摘基于有限体积三维水动力海洋数值模型FVCOM(Finite-Volume Community Ocean Model)对库克海峡邻近海域的潮汐潮流进行了数值模拟分析,同时搜集了验潮站的潮位数据及其潮汐调和分析数据,对模型结果进行了对比验证。结果表明,库克海峡两侧潮汐存在着显著差异,北侧由新西兰海岸向塔斯曼海的方向上,振幅逐渐降低,南侧由南部宽阔海域向新西兰南部岸线的方向上,振幅逐渐升高,且该区域的潮汐过程受地形和岸线影响较大。库克海峡中部存在典型的往复流,且以向南流动为主。库克海峡南侧存在的隆起地形和海沟是海峡之外该海域潮汐过程的重要影响因子,具体表现在南部海洋中隆起区域的潮流流速显著增加,流向也随之改变。与实测资料的对比结果表明,本研究的数值模拟结果与实测资料基本吻合,能够准确地模拟库克海峡邻近海域的潮汐潮流状况,为相关海洋工程建设以及科学研究等提供了重要的试验依据。
基金support by Fondazione Cariplo and Fondazione CDP(Italy)under the project No.2022-1895.
文摘We construct an unconventional divergence preserving discretization of updated Lagrangian ideal magnetohydrodynamics(MHD)over simplicial grids.The cell-centered finite-volume(FV)method employed to discretize the conservation laws of volume,momentum,and total energy is rigorously the same as the one developed to simulate hyperelasticity equations.By construction this moving mesh method ensures the compatibility between the mesh displacement and the approximation of the volume flux by means of the nodal velocity and the attached unit corner normal vector which is nothing but the partial derivative of the cell volume with respect to the node coordinate under consideration.This is precisely the definition of the compatibility with the Geometrical Conservation Law which is the cornerstone of any proper multi-dimensional moving mesh FV discretization.The momentum and the total energy fluxes are approximated utilizing the partition of cell faces into sub-faces and the concept of sub-face force which is the traction force attached to each sub-face impinging at a node.We observe that the time evolution of the magnetic field might be simply expressed in terms of the deformation gradient which characterizes the Lagrange-to-Euler mapping.In this framework,the divergence of the magnetic field is conserved with respect to time thanks to the Piola formula.Therefore,we solve the fully compatible updated Lagrangian discretization of the deformation gradient tensor for updating in a simple manner the cell-centered value of the magnetic field.Finally,the sub-face traction force is expressed in terms of the nodal velocity to ensure a semi-discrete entropy inequality within each cell.The conservation of momentum and total energy is recovered prescribing the balance of all the sub-face forces attached to the sub-faces impinging at a given node.This balance corresponds to a vectorial system satisfied by the nodal velocity.It always admits a unique solution which provides the nodal velocity.The robustness and the accuracy of this unconventional FV scheme have been demonstrated by employing various representative test cases.Finally,it is worth emphasizing that once you have an updated Lagrangian code for solving hyperelasticity you also get an almost free updated Lagrangian code for solving ideal MHD ensuring exactly the compatibility with the involution constraint for the magnetic field at the discrete level.
文摘基于FVCOM(Finite-Volu me Coastal Ocean Model)三维水动力模型,将整个渤海海域及其邻近的黄海北部海域作为研究海域,以8个主要分潮(M_(2),S_(2),K_(2),N_(2),K_(1),O_(1),P_(1),Q_(1))调和分析得到的水位驱动开边界,对研究海域的潮汐、潮流进行了数值模拟。文章通过对模拟结果中的水位数据和流场数据进行调和分析,绘制了研究海域的四大主要分潮(M_(2),S_(2),K_(1),O_(1))的同潮时图、潮流椭圆分布图,分析判断了研究海域的潮汐、潮流类型。经过对比分析,与公认的结果非常一致,说明了FVCOM模型能够很好地模拟近海的潮汐潮流。
基金supported jointly by Strategic Pilot Science and Technology Project of Chinese Academy of Sciences (No. XDA14020102)National key research and development plan (No. 2017YFC0601805)+5 种基金National Natural Science Foundation of China (No. 41574110)Youth Foundation of Hebei Educational Committee (No. QN2018217)Hebei Higher Education Teaching Reform Research and Practice(No. 2018GJJG328)Zhangjiakou science and technology bureau(No. 1821011B)Doctoral Fund of Hebei Institute of Architecture and Civil Engineering (No. B-201606)Academic Team Innovation Ability Improvement Project of Hebei Institute of Architecture and Civil Engineering(TD202011)。
文摘In this study,the cylindrical finite-volume method(FVM)is advanced for the efficient and high-precision simulation of the logging while drilling(LWD)orthogonal azimuth electromagnetic tool(OAEMT)response in a three-dimensional(3 D)anisotropic formation.To overcome the ill-condition and convergence problems arising from the low induction number,Maxwell’s equations are reformulated into a mixed Helmholtz equation for the coupled potentials in a cylindrical coordinate system.The electrical fi eld continuation method is applied to approximate the perfectly electrical conducting(PEC)boundary condition,to improve the discretization accuracy of the Helmholtz equation on the surface of metal mandrels.On the base,the 3 D FVM on Lebedev’s staggered grids in the cylindrical coordinates is employed to discretize the mixed equations to ensure good conformity with typical well-logging tool geometries.The equivalent conductivity in a non-uniform element is determined by a standardization technique.The direct solver,PARDISO,is applied to efficiently solve the sparse linear equation systems for the multi-transmitter problem.To reduce the number of calls to PARDISO,the whole computational domain is divided into small windows that contain multiple measuring points.The electromagnetic(EM)solutions produced by all the transmitters per window are simultaneously solved because the discrete matrix,relevant to all the transmitters in the same window,is changed.Finally,the 3 D FVM is validated against the numerical mode matching method(NMM),and the characteristics of both the coaxial and coplanar responses of the EM field tool are investigated using the numerical results.
文摘A finite-volume charge method has been proposed to simulate PIN diodes and insulated-gate bipolar transistor(IGBT)devices using SPICE simulators by extending the lumped-charge method.The new method assumes local quasi-neutrality in the undepleted N^(-)base region and uses the total collector current,the nodal hole density and voltage as the basic quantities.In SPICE implementation,it makes clear and accurate definitions of three kinds of nodes—the carrier density nodes,the voltage nodes and the current generator nodes—in the undepleted N^(-)base region.It uses central finite difference to approximate electron and hole current generators and sets up the current continuity equation in a control volume for every carrier density node in the undepleted N^(-)base region.It is easy to increase the number of nodes to describe the fast spatially varying carrier density in transient processes.We use this method to simulate IGBT devices in SPICE simulators and get a good agreement with technology computer-aided design simulations.
文摘In this paper, a stochastic finite-volume solver based on polynomial chaos expansion is developed. The upwind scheme is used to avoid the numerical instabilities. The Burgers’ equation subjected to deterministic boundary conditions and random viscosity is solved. The solution uncertainty is quantified for different values of viscosity. Monte-Carlo simulations are used to validate and compare the developed solver. The mean, standard deviation and the probability distribution function (p.d.f) of the stochastic Burgers’ solution is quantified and the effect of some parameters is investigated. The large sparse linear system resulting from the stochastic solver is solved in parallel to enhance the performance. Also, Monte-Carlo simulations are done in parallel and the execution times are compared in both cases.
