The Experts below are selected from a list of 5328 Experts worldwide ranked by ideXlab platform
Yuri Feldman - One of the best experts on this subject based on the ideXlab platform.
-
a semi implicit direct forcing immersed boundary method for periodically moving immersed bodies a Schur Complement approach
Computer Methods in Applied Mechanics and Engineering, 2021Co-Authors: Rafi Sela, Efi Zemach, Yuri FeldmanAbstract:Abstract An extended immersed boundary methodology utilizing a semi-implicit direct forcing approach was formulated for the simulation of incompressible flows in the presence of periodically moving immersed bodies. The methodology utilizes a Schur Complement approach to enforce no-slip kinematic constraints for immersed surfaces. The methodology is split into an “embarrassingly” parallel pre-computing stage and a time integration stage, both of which take advantage of the general parallel file system (GPFS) for efficient writing and reading of large amounts of data. The methodology can be embedded straight forwardly into the whole family of pressure–velocity segregated solvers of incompressible Navier–Stokes equations based on projection or fractional step approaches. The methodology accurately meets the no-slip kinematic constraints on the surfaces of immersed oscillating bodies. In this study, it was extensively verified by applying it for the simulation of a number of representative flows developing in the presence of an oscillating sphere. The capabilities of the methodology for the simulation of incompressible flow generated by a number of bodies whose motion is governed by general periodic kinematics were demonstrated by simulation of the flow developing in the presence of two out-of-phase oscillating spheres. The physical characteristics of the generated flows in terms of the time evolutions of the total drag coefficients were presented as a function of Reynolds values. The vortical structures inherent in the generated flows were visualized by presenting the isosurfaces of the λ 2 criterion.
-
semi implicit direct forcing immersed boundary method for incompressible viscous thermal flow problems a Schur Complement approach
International Journal of Heat and Mass Transfer, 2018Co-Authors: Yuri FeldmanAbstract:Abstract An extended immersed boundary method utilizing a semi-implicit direct forcing approach for the simulation of confined incompressible viscous thermal flow problems is presented. The method utilizes a Schur Complement approach to enforce the kinematic constraints of no-slip and the corresponding thermal boundary conditions for immersed surfaces. The developed methodology can be straightforwardly adapted to any existing incompressible time marching solver based on a segregated pressure-velocity coupling. The method accurately meets the thermal and the no-slip boundary conditions on the surfaces of immersed bodies for the entire range of Rayleigh numbers 10 3 ⩽ Ra ⩽ 10 6 . Strategies for further increasing the computational efficiency of the developed approach are discussed. The method has been extensively verified by applying it for the simulation of a number of representative fully 3D confined natural convection steady and periodic flows. Complex dynamic phenomena typical of this kind of flow including vortical structures and convection cells and instability characteristics, were simulated and visualized and the results were found to compare favorably with results known from literature.
-
semi implicit direct forcing immersed boundary method for incompressible viscous thermal flow problems a Schur Complement approach
arXiv: Fluid Dynamics, 2017Co-Authors: Yuri FeldmanAbstract:An extended immersed boundary method utilizing a semi-implicit direct forcing approach for the simulation of confined incompressible viscous thermal flow problems is presented. The method utilizes a Schur Complement approach to enforce the kinematic constraints of no-slip and the corresponding thermal boundary conditions for immersed surfaces. The developed methodology can be straightforwardly adapted to any existing incompressible time marching solver based on a segregated pressure-velocity coupling. The method accurately meets the thermal and the no-slip boundary conditions on the surfaces of immersed bodies for the entire range of Rayleigh numbers $10^3\leqslant Ra\leqslant10^6$. Strategies for further increasing the computational efficiency of the developed approach are discussed. The method has been extensively verified by applying it for the simulation of a number of representative fully 3D confined natural convection steady and periodic flows. Complex dynamic phenomena typical of this kind of flow including vortical structures and convection cells and instability characteristics, were simulated and visualized and the results were found to compare favorably with results known from literature.
Byung Chai Lee - One of the best experts on this subject based on the ideXlab platform.
-
aggregation multigrid method for Schur Complement system in fe analysis of continuum elements
Structural Engineering and Mechanics, 2008Co-Authors: Byung Chai LeeAbstract:An aggregation multigrid method (AMM) is a leading iterative solver in solid mechanics. Recently, AMM is applied for solving Schur Complement system in the FE analysis of shell structures. In this work, an extended application of AMM for solving Schur Complement system in the FE analysis of continuum elements is presented. Further, the performance of the proposed AMM in multiple load cases, which is a challenging problem for an iterative solver, is studied. The proposed method is developed by combining the substructuring and the multigrid methods. The substructuring method avoids factorizing the full-size matrix of an original system and the multigrid method gives near-optimal convergence. This method is demonstrated for the FE analysis of several elastostatic problems. The numerical results show better performance by the proposed method as compared to the preconditioned conjugate gradient method. The smaller computational cost for the iterative procedure of the proposed method gives a good alternative to a direct solver in large systems with multiple load cases.
-
preconditioning Schur Complement matrices based on an aggregation multigrid method for shell structures
Computers & Structures, 2006Co-Authors: Byung Chai LeeAbstract:An aggregation multigrid method is utilized in constructing a preconditioner for a Schur Complement system of automatically partitioned, non-overlapping subdomains. Preserving the relationship of the partitioned subdomains, we apply a rigid body based aggregation method, which employ geometric data, as a coarsening procedure. And then, we derive a new Schur Complement coarse grid matrix by an approach of a condensation after the coarsening procedure. Therefore, we generate a multi-level preconditioner of a Krylov subspace method for Schur Complement matrices using the coarse grid matrix. Through numerical experiments, the proposed preconditioner shows efficient performance and robust convergences irrespect of the size of elements and subdomains. It also shows better performance than the preconditioned conjugate gradient method (PCG) for the partitioned system and the aggregation multigrid method for the original domain in shell problems of structural mechanics.
Thierry Van Cutsem - One of the best experts on this subject based on the ideXlab platform.
-
power system dynamic simulations using a parallel two level Schur Complement decomposition
IEEE Transactions on Power Systems, 2016Co-Authors: Petros Aristidou, Simon Lebeau, Thierry Van CutsemAbstract:As the need for faster power system dynamic simulations increases, it is essential to develop new algorithms that exploit parallel computing to accelerate those simulations. This paper proposes a parallel algorithm based on a two-level, Schur-Complement-based, domain decomposition method. The two-level partitioning provides high parallelization potential (coarse- and fine-grained). In addition, due to the Schur-Complement approach used to update the sub-domain interface variables, the algorithm exhibits high global convergence rate. Finally, it provides significant numerical and computational acceleration. The algorithm is implemented using the shared-memory parallel programming model, targeting inexpensive multi-core machines. Its performance is reported on a real system as well as on a large test system combining transmission and distribution networks.
-
dynamic simulation of large scale power systems using a parallel Schur Complement based decomposition method
IEEE Transactions on Parallel and Distributed Systems, 2014Co-Authors: Petros Aristidou, Davide Fabozzi, Thierry Van CutsemAbstract:Power system dynamic simulations are crucial for the operation of electric power systems as they provide important information on the dynamic evolution of the system after an occurring disturbance. This paper proposes a robust, accurate and efficient parallel algorithm based on the Schur Complement domain decomposition method. The algorithm provides numerical and computational acceleration of the procedure. Based on the shared-memory parallel programming model, a parallel implementation of the proposed algorithm is presented. The implementation is general, portable and scalable on inexpensive, shared-memory, multi-core machines. Two realistic test systems, a medium-scale and a large-scale, are used for performance evaluation of the proposed method.
-
a Schur Complement method for dae systems in power system dynamic simulations
2014Co-Authors: Petros Aristidou, Davide Fabozzi, Thierry Van CutsemAbstract:This paper proposes a Schur Complement-based Domain Decomposition Method to accelerate the time-domain simulation of large, non-linear and stiff Differential and Algebraic Equation systems stemming from power system dynamic studies. The proposed algorithm employs a star-shaped decomposition scheme and exploits the locality and sparsity of the system. The simulation is accelerated by the use of quasi-Newton schemes and parallel programming techniques. The proposed algorithm is implemented using the shared-memory parallel programming model and tested on a large-scale, realistic power system model showing significant speedup.
Rafi Sela - One of the best experts on this subject based on the ideXlab platform.
-
a semi implicit direct forcing immersed boundary method for periodically moving immersed bodies a Schur Complement approach
Computer Methods in Applied Mechanics and Engineering, 2021Co-Authors: Rafi Sela, Efi Zemach, Yuri FeldmanAbstract:Abstract An extended immersed boundary methodology utilizing a semi-implicit direct forcing approach was formulated for the simulation of incompressible flows in the presence of periodically moving immersed bodies. The methodology utilizes a Schur Complement approach to enforce no-slip kinematic constraints for immersed surfaces. The methodology is split into an “embarrassingly” parallel pre-computing stage and a time integration stage, both of which take advantage of the general parallel file system (GPFS) for efficient writing and reading of large amounts of data. The methodology can be embedded straight forwardly into the whole family of pressure–velocity segregated solvers of incompressible Navier–Stokes equations based on projection or fractional step approaches. The methodology accurately meets the no-slip kinematic constraints on the surfaces of immersed oscillating bodies. In this study, it was extensively verified by applying it for the simulation of a number of representative flows developing in the presence of an oscillating sphere. The capabilities of the methodology for the simulation of incompressible flow generated by a number of bodies whose motion is governed by general periodic kinematics were demonstrated by simulation of the flow developing in the presence of two out-of-phase oscillating spheres. The physical characteristics of the generated flows in terms of the time evolutions of the total drag coefficients were presented as a function of Reynolds values. The vortical structures inherent in the generated flows were visualized by presenting the isosurfaces of the λ 2 criterion.
Shanhui Fan - One of the best experts on this subject based on the ideXlab platform.
-
accelerating adjoint variable method based photonic optimization with Schur Complement domain decomposition
arXiv: Computational Physics, 2019Co-Authors: Nathan Zhao, Salim Boutami, Shanhui FanAbstract:Adjoint variable method in combination with gradient descent optimization has been widely used for the inverse design of nanophotonic devices. In many of such optimizations, the design region is only a small fraction of the total computational domain. Here we show that the adjoint variable method can be combined with the Schur Complement domain decomposition method. With this combination, in each optimization step, the simulation only involves the degrees of freedom that are inside the design region. Our approach should significantly improve the computational efficiency of adjoint variable method based optimization of photonic structures.
-
accelerating simulation of ensembles of locally differing optical structures via a Schur Complement domain decomposition
Optics Letters, 2014Co-Authors: Sacha Verweij, Victor Liu, Shanhui FanAbstract:We present a Schur Complement domain decomposition method that can significantly accelerate simulation of ensembles of locally differing optical structures. We apply the method to design a multi-spatial-mode photonic crystal waveguide splitter that exhibits high transmission and preservation of modal content, showing design acceleration by more than a factor of 20.
