scholarly journals Admissible and Attainable Convergence Behavior of Block Arnoldi and GMRES

2020 ◽  
Vol 41 (2) ◽  
pp. 464-486
Author(s):  
Marie Kubínová ◽  
Kirk M. Soodhalter
Keyword(s):  
Convergence Behavior ◽  
Block Arnoldi

Calculation of rightmost eigenvalues in power systems using the block Arnoldi Chebyshev method (BACM)

2003 ◽  
Vol 150 (1) ◽  
pp. 23 ◽  
Author(s):  
B. Lee ◽  
H. Song ◽  
S.-H. Kwon ◽  
D. Kim ◽  
K. Iba ◽  
...  
Keyword(s):  
Power Systems ◽  
Chebyshev Method ◽  
Block Arnoldi

Determination of Base Flipping Free Energy Landscapes from Nonequilibrium Stratification

2019 ◽  
Author(s):  
Xiaohui Wang ◽  
Zhaoxi Sun
Keyword(s):  
Free Energy ◽  
Energy Landscape ◽  
Sampling Technique ◽  
Umbrella Sampling ◽  
Energy Simulation ◽  
Nonlinear Dependence ◽  
Free Energy Landscape ◽  
Convergence Criterion ◽  
Base Flipping ◽  
Convergence Behavior

<p>Correct calculation of the variation of free energy upon base flipping is crucial in understanding the dynamics of DNA systems. The free energy landscape along the flipping pathway gives the thermodynamic stability and the flexibility of base-paired states. Although numerous free energy simulations are performed in the base flipping cases, no theoretically rigorous nonequilibrium techniques are devised and employed to investigate the thermodynamics of base flipping. In the current work, we report a general nonequilibrium stratification scheme for efficient calculation of the free energy landscape of base flipping in DNA duplex. We carefully monitor the convergence behavior of the equilibrium sampling based free energy simulation and the nonequilibrium stratification and determine the empirical length of time blocks required for converged sampling. Comparison between the performances of equilibrium umbrella sampling and nonequilibrium stratification is given. The results show that nonequilibrium free energy simulation is able to give similar accuracy and efficiency compared with the equilibrium enhanced sampling technique in the base flipping cases. We further test a convergence criterion we previously proposed and it comes out that the convergence behavior determined by this criterion agrees with those given by the time-invariant behavior of PMF and the nonlinear dependence of standard deviation on the sample size. </p>

Coupling-dependent convergence behavior of phase oscillators with tegotae-control

2021 ◽  
Author(s):  
Simon Hauser ◽  
Matthieu Dujany ◽  
Jonathan Arreguit ◽  
Auke Ijspeert ◽  
Fumiya Iida
Keyword(s):  
Phase Oscillators ◽  
Convergence Behavior

Application of advanced RANS turbulence models for the prediction of turbomachinery flows

2021 ◽  
pp. 1-13
Author(s):  
Ernesto Casartelli ◽  
Luca Mangani ◽  
David Roos Launchbury ◽  
Armando Del Rio
Keyword(s):  
Design Process ◽  
Current Trend ◽  
Turbulence Models ◽  
Stability Limit ◽  
Transport Equations ◽  
Stability And Convergence ◽  
Operating Characteristics ◽  
Convergence Behavior ◽  
Anisotropic Turbulence ◽  
Rans Models

Abstract The current trend in turbomachinery towards broader operating characteristics requires that operating points in the off-design region can be captured accordingly from the simulation models. Complex processes like separation and vortex formation/dissipation occur under these conditions. Linear two equation models are often not able to represent these effects correctly since their derivation is based on over-simplifications, such as the Boussinesq hypothesis, which makes it impossible to capture anisotropic turbulence. Advanced RANS models are usually not considered in the design process of turbomachines because (1) they are usually more delicate with regards to stability and convergence behavior and (2) require additional computational effort. To make the usage of advanced RANS models more applicable for complex turbomachinery simulations a selected group of models were implemented into a robust framework of a pressure-based fully coupled solver. To further enhance stability, coupling terms between the turbulent transport equations were derived for several models. Anisotropic turbulence is introduced by computing an algebraic expression or by solving the transport equations for the Reynolds stress components. The evaluation of the models is performed on the RWTH Aachen “Radiver” centrifugal compressor case with vaned diffuser. For design conditions and operation points near the stability limit, all investigated turbulence models predict the compressor characteristic. Operation points in the choking region on the other hand are only predicted well by anisotropic models. The good results and improved convergence behavior of the advanced RANS models clearly indicates their applicability in the design process of turbomachines.

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