Research and application of small time-step simulation for MMC VSC-HVDC in RTDS

2014 ◽  
Author(s):  
Kaijian Ou ◽  
Trevor Maguire ◽  
Bruce Warkentin ◽  
Yuan Chen ◽  
Yi Zhang ◽  
...  
Keyword(s):  
Small Time ◽  
Time Step ◽  
Small Time Step

Load Discontinuity and Its Remedy in Step-by-Step Integration

2006 ◽  
Author(s):  
Shuenn-Yih Chang ◽  
Chiu-Li Huang
Keyword(s):  
Numerical Solution ◽  
Small Time ◽  
Step Size ◽  
Time Step ◽  
Integration Procedure ◽  
Amplitude Distortion ◽  
Small Time Step

The discontinuity at the end of an impulse will lead to an extra impulse and thus an extra displacement. Consequently, an amplitude distortion is introduced in the numerical solution. The difficulty arising from the discontinuity at the end of an impulse can be overcome by using a very small time step to perform the step-by-step integration since it reduces the extra impulse and thus extra displacement. However, computational efforts might be significantly increased since the small time step is performed for a complete step-by-step integration procedure. A remedy is devised to computationally efficiently overcome this difficulty by using a very small time step immediately upon termination of the applied impulse. This is because that the extra impulse caused by the discontinuity is almost proportional to the discontinuity value at the end of the impulse and the step size. The feasibility of this proposed remedy is analytically and numerically confirmed herein.

Simulation of Red Blood Cell Passing Through Constrictions Using Modified Moving Particle Semi-Implicit Method

2011 ◽  
Author(s):  
K. Firoozbakhsh ◽  
M. T. Ahmadian ◽  
M. Hasanian
Keyword(s):  
Mechanical Behavior ◽  
Experimental Studies ◽  
Small Time ◽  
Implicit Method ◽  
Parallel Plates ◽  
Time Step ◽  
Mps Method ◽  
Time Step Size ◽  
Small Time Step ◽  
Moving Particle

During the circulation of RBC it undergoes elastic deformation as it passes through micro-capillaries where the inner diameter of the constriction can be about 3 micro meters. It means RBC shape must be changed in order to pass through these narrow channels. The role of mechanical behavior of RBC and the deformability traits of RBC are observed with the several experimental studies [1]. Several methods were implemented to simulate the mechanical behavior of RBCs in micro-capillaries [1, 2]. One of the most recent methods is Moving Particle Semi-implicit method (MPS) which is a Lagrangian method with semi-implicit algorithm that guaranties the incompressibility of the fluid. MPS method was implemented for simulation of RBC motion through parallel plates by Tsubota et al. 2006 [3]. Due to small Reynolds number and the Diffusion number restrictions, implementation of small time step size would be necessary which leads to long time simulation. By the way in case of complex geometries or FSI problems, standard MPS method has a delicate pressure solver which leads to diverge the solution. So in these cases using a small time step can help to overcome the problem. Some studies have applied a new approach for time integration and the fractional time step method is employed to overcome the noticed problem. Yohsuke Imai and coworkers (2010) have developed the former studies with two main new approaches [4]. Firstly, evaluation of viscosity is upgraded and secondly boundary condition is assumed to be periodic. Although the developments are really impressive and MPS method has turned into a practical method for simulation of RBC motion in micro-capillaries, but still there are some considerations about using large time steps and error of the velocity profile consequently.

scholarly journals A diffusion Monte Carlo algorithm with very small time‐step errors

1993 ◽  
Vol 99 (4) ◽  
pp. 2865-2890 ◽  
Author(s):  
C. J. Umrigar ◽  
M. P. Nightingale ◽  
K. J. Runge
Keyword(s):  
Monte Carlo ◽  
Small Time ◽  
Monte Carlo Algorithm ◽  
Diffusion Monte Carlo ◽  
Time Step ◽  
Small Time Step

Stability Analysis Research of Modified CD-Newmark Numerical Integral Method in Seismic Pseudo-Dynamic Test

2014 ◽  
Vol 638-640 ◽  
pp. 1869-1872
Author(s):  
Xin Jiang Cai ◽  
Shi Zhu Tian
Keyword(s):  
Integral Method ◽  
Dynamic Test ◽  
Stable Condition ◽  
Small Time ◽  
Stability Conditions ◽  
Newmark Method ◽  
Time Step ◽  
Unconditionally Stable ◽  
Small Time Step ◽  
Numerical Integral

The characteristics of explicit numerical integral method is without iteration, and the characteristics of inexplicit numerical integral method is unconditionally stable. The traditional CD-Newmark method has the shortcoming of the bigger upper frequency leads to a small time step, a modified combined integral method named MCD-Newmark release the fixed DOF of numerical substructure, then obtained the parameters range of stable condition of experimental substructure, and the unconditionally stable of numerical substructure is also researched,then the strict stability conditions of the traditional CD-Newmark algorithm is resolved. The study provides reference for structural seismic test.

scholarly journals Convergence Improved Lax-Friedrichs Scheme Based Numerical Schemes and Their Applications in Solving the One-Layer and Two-Layer Shallow-Water Equations

2015 ◽  
Vol 2015 ◽  
pp. 1-10
Author(s):  
Xinhua Lu ◽  
Bingjiang Dong ◽  
Bing Mao ◽  
Xiaofeng Zhang
Keyword(s):  
High Resolution ◽  
Shallow Water ◽  
Shallow Water Equations ◽  
Small Time ◽  
Numerical Schemes ◽  
Time Step ◽  
Numerical Diffusion ◽  
First Order ◽  
Small Time Step ◽  
The One

The first-order Lax-Friedrichs (LF) scheme is commonly used in conjunction with other schemes to achieve monotone and stable properties with lower numerical diffusion. Nevertheless, the LF scheme and the schemes devised based on it, for example, the first-order centered (FORCE) and the slope-limited centered (SLIC) schemes, cannot achieve a time-step-independence solution due to the excessive numerical diffusion at a small time step. In this work, two time-step-convergence improved schemes, the C-FORCE and C-SLIC schemes, are proposed to resolve this problem. The performance of the proposed schemes is validated in solving the one-layer and two-layer shallow-water equations, verifying their capabilities in attaining time-step-independence solutions and showing robustness of them in resolving discontinuities with high-resolution.

PSEUDODYNAMIC TECHNIQUE TO OBTAIN RELIABLE SHOCK RESPONSE

2013 ◽  
Vol 14 (01) ◽  
pp. 1350050 ◽  
Author(s):  
SHUENN-YIH CHANG ◽  
TING-WEI CHEN ◽  
CHING-HAO YANG
Keyword(s):  
Small Time ◽  
Impulsive Loading ◽  
Time Step ◽  
Linear Elastic ◽  
Testing Method ◽  
Elastic Systems ◽  
Shock Response ◽  
Small Time Step ◽  
Pseudodynamic Testing ◽  
Test Result

The use of a pseudodynamic testing method to obtain a response from an impulsive loading may lead to an incorrect test result even though the test setup is properly adjusted and the time step is appropriately chosen based on general considerations. The cause to this problem is analytically explored and a pseudodynamic technique is proposed to overcome this difficulty. The technique is to perform a single small time step immediately upon termination of the applied impulse, while the other time steps can still be conducted by the time step determined from general considerations. The feasibility of this technique is analytically verified and confirmed by a series of pseudodynamic tests for both linear elastic systems and inelastic systems.

Sign in / Sign up

Export Citation Format

Share Document