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CISE301 : Numerical Methods Topic 8 Ordinary Differential Equations (ODEs) Lecture 28-36. KFUPM Read 25.1-25.4, 26-2, 27-1. Outline of Topic 8. Lesson 1: Introduction to ODEs Lesson 2: Taylor series methods Lesson 3: Midpoint and Heun’s method Lessons 4-5: Runge-Kutta methods
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CISE301: Numerical MethodsTopic 8Ordinary Differential Equations (ODEs)Lecture 28-36 KFUPM Read 25.1-25.4, 26-2, 27-1 KFUPM
Outline of Topic 8 • Lesson 1: Introduction to ODEs • Lesson 2: Taylor series methods • Lesson 3: Midpoint and Heun’s method • Lessons 4-5: Runge-Kutta methods • Lesson 6: Solving systems of ODEs • Lesson 7: Multiple step Methods • Lesson 8-9: Boundary value Problems KFUPM
Learning Objectives of Lesson 4 • To understand the motivation for using Runge-Kutta (RK) method and the basic idea used in deriving them. • To get familiar with Taylor series for functions of two variables. • To use RK method of order 2 to solve ODEs. KFUPM
Motivation • We seek accurate methods to solve ODEs that do not require calculating high order derivatives. • The approach is to use a formula involving unknown coefficients then determine these coefficients to match as many terms of the Taylor series expansion as possible. KFUPM
Runge-Kutta Method KFUPM
Taylor Series in Two Variables The Taylor Series discussed in Chapter 4 is extended to the 2-independent variable case. This is used to prove RK formula. KFUPM
Taylor Series in One Variable Approximation Error KFUPM
Definitions KFUPM
Taylor Series Expansion KFUPM
Taylor Series in Two Variables y+k y x x+h KFUPM
Runge-Kutta Method KFUPM
Runge-Kutta Method KFUPM
Runge-Kutta Method KFUPM
Runge-Kutta Method KFUPM
Runge-Kutta Method KFUPM
Summary • RK methods generate an accurate solution without the need to calculate high order derivatives. • Second order RK have local truncation error of order O(h3). • Fourth order RK have local truncation error of order O(h5). • N function evaluations are needed in the Nth order RK method. KFUPM
Lecture 32Lesson 5: Applications of Runge-Kutta Methods to Solve First Order ODEs KFUPM
Learning Objectives of Lesson 5 • Use Runge-Kutta methods of different orders to solve first order ODEs. KFUPM
Runge-Kutta Method KFUPM
Runge-Kutta Methods RK2 KFUPM
Runge-Kutta Methods RK3 KFUPM
Runge-Kutta Methods RK4 KFUPM
Runge-Kutta Methods Higher order Runge-Kutta methods are available. Higher order methods are more accurate but require more calculations. Fourth order is a good choice. It offers good accuracy with a reasonable calculation effort. KFUPM
Example 1Summary of the solution Summary of the solution KFUPM
Solution after 100 steps KFUPM
Example 24th-Order Runge-Kutta Method See RK4 Formula KFUPM
Example 2Fourth Order Runge-Kutta Method See RK4 Formula KFUPM
Runge-Kutta Methods RK4 KFUPM
Example 2Summary of the solution Summary of the solution KFUPM
Remaining Lessons in Topic 8 Lesson 6: Solving Systems of high order ODE Lesson 7: Multi-step methods Lessons 8-9: Methods to solve Boundary Value Problems KFUPM