Sökning: "Convergence Acceleration"

Visar resultat 1 - 5 av 20 avhandlingar innehållade orden Convergence Acceleration.

1. 1. Convergence Acceleration for Flow Problems

   Författare :Henrik Brandén; Sverker Holmgren; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Computational fluid dynamics; convergence acceleration; semicirculant preconditioning; fundamental solutions; Numerical Analysis; Numerisk analys;

   Sammanfattning : Convergence acceleration techniques for the iterative solution of system of equations arising in the discretisations of compressible flow problems governed by the steady state Euler or Navier-Stokes equations is considered. The system of PDE is discretised using a finite difference or finite volume method yielding a large sparse system of equations. LÄS MER

3. 2. Acceleration of Compressible Flow Simulations with Edge using Implicit Time Stepping

   Författare :Evelyn Otero; Arthur Rizzi; Jesper Oppelstrup; Per Wahlund; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; compressible CFD; convergence acceleration; implicit time-stepping; matrix dissipation; line-implicit; performance optimization;

   Sammanfattning : Computational fluid dynamics (CFD) has become a significant tool routinely used in design and optimization in aerospace industry. Typical flows may be characterized by high-speed and compressible flow features and, in many cases, by massive flow separation and unsteadiness. LÄS MER

4. 3. Acceleration of Compressible Flow Simulations with Edge Using  Implicit Time Stepping

   Författare :Evelyn Otero; Arthur Rizzi; Richard P. Dwight; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Compressible CFD; Convergence Acceleration; Implicit Time-Stepping; LU-SGS; Upwind Type Dissipation; Line-implicit; Ordering; Parallelization; Parameters; Multigrid;

   Sammanfattning : Computational fluid dynamics (CFD) is a significant tool routinely used indesign and optimization in aerospace industry. Often cases with unsteadyflows must be computed, and the long compute times of standard methods hasmotivated the present work on new implicit methods to replace the standardexplicit schemes. LÄS MER

5. 4. Accuracy and Convergence Studies of the Numerical Solution of Compressible Flow Problems

   Författare :Erik Sterner; Per Lötstedt; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; computational fluid dynamics; Navier-Stokes equations; convergence acceleration; preconditioning; semi-implicit; multiblock; multigrid; finite volume method; Numerical Analysis; Numerisk analys;

   Sammanfattning : The numerical solution of compressible flow problems governed by the Navier-Stokes equations is considered. A finite volume method is used for the discretization in space. Different techniques to accelerate the convergence to a steady state are suggested, and the accuracy of the spatial difference operator is analyzed. LÄS MER

7. 5. Scalable Optimization Methods for Machine Learning : Acceleration, Adaptivity and Structured Non-Convexity

   Författare :Vien Van Mai; Mikael Johansson; John Duchi; KTH; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Large-scale optimization; Anderson acceleration; first-order methods; stochastic optimization; momentum; gradient clipping; Electrical Engineering; Elektro- och systemteknik;

   Sammanfattning : This thesis aims at developing efficient optimization algorithms for solving large-scale machine learning problems. To cope with the increasing scale and complexity of such models, we focus on first-order and stochastic methods in which updates are carried out using only (noisy) information about function values and (sub)gradients. LÄS MER