scholarly journals A New Block Preconditioner for Implicit Runge--Kutta Methods for Parabolic PDE Problems

2021 ◽  
pp. S475-S495
Author(s):  
Md. Masud Rana ◽  
Victoria E. Howle ◽  
Katharine Long ◽  
Ashley Meek ◽  
William Milestone
1997 ◽  
Author(s):  
Jack Yoh ◽  
Xiaolin Zhong ◽  
Jack Yoh ◽  
Xiaolin Zhong
Keyword(s):  

2015 ◽  
Vol 11 (1) ◽  
Author(s):  
W. Vásquez ◽  
J. Játiva
Keyword(s):  

En este trabajo se presenta la modelación de los componentes aerodinámicos, mecánicos, eléctricos y de control del aerogenerador con generador de inducción doblemente alimentado (DFIG). La modelación es empleada para crear un programa en el software Matlab. Se utiliza el método de Runge Kutta de cuarto orden para solucionar las ecuaciones diferenciales existentes en la modelación. La estrategia de control del convertidor PWM bidireccional se base en la técnica de control vectorial que emplea marcos de referencia giratorios, la cual permite el control de las potencias activa y reactiva producidas por el DFIG. Se describe el proceso de inicialización del sistema aerogenerador con DFIG, para obtener las condiciones de estado estable antes de iniciar la simulación. Se analiza el comportamiento del aerogenerador con DFIG ante cambios de la velocidad del viento y fallas de corto circuito. Los resultados finales muestran que la potencia activa del DFIG varía de acuerdo al comportamiento de la velocidad del viento, mientras que la potencia reactiva permanece casi invariante. Los resultados obtenidos son comparados con los resultados del modelo del aerogenerador con DFIG existente en Simulink de Matlab.


Mathematics ◽  
2021 ◽  
Vol 9 (13) ◽  
pp. 1483
Author(s):  
Shanqin Chen

Weighted essentially non-oscillatory (WENO) methods are especially efficient for numerically solving nonlinear hyperbolic equations. In order to achieve strong stability and large time-steps, strong stability preserving (SSP) integrating factor (IF) methods were designed in the literature, but the methods there were only for one-dimensional (1D) problems that have a stiff linear component and a non-stiff nonlinear component. In this paper, we extend WENO methods with large time-stepping SSP integrating factor Runge–Kutta time discretization to solve general nonlinear two-dimensional (2D) problems by a splitting method. How to evaluate the matrix exponential operator efficiently is a tremendous challenge when we apply IF temporal discretization for PDEs on high spatial dimensions. In this work, the matrix exponential computation is approximated through the Krylov subspace projection method. Numerical examples are shown to demonstrate the accuracy and large time-step size of the present method.


Mathematics ◽  
2021 ◽  
Vol 9 (16) ◽  
pp. 1842
Author(s):  
Vladislav N. Kovalnogov ◽  
Ruslan V. Fedorov ◽  
Yuri A. Khakhalev ◽  
Theodore E. Simos ◽  
Charalampos Tsitouras

We consider the scalar autonomous initial value problem as solved by an explicit Runge-Kutta pair of orders 6 and 5. We focus on an efficient family of such pairs, which were studied extensively in previous decades. This family comes with 5 coefficients that one is able to select arbitrarily. We set, as a fitness function, a certain measure, which is evaluated after running the pair in a couple of relevant problems. Thus, we may adjust the coefficients of the pair, minimizing this fitness function using the differential evolution technique. We conclude with a method (i.e. a Runge-Kutta pair) which outperforms other pairs of the same two orders in a variety of scalar autonomous problems.


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