1 EMT 101 – Engineering Programming Dr. Farzad Ismail School of Aerospace Engineering Universiti Sains Malaysia Nibong Tebal Pulau Pinang Week 9

2 Abundance of point data? As seen in Homework 2, the computer produces point data which are difficult to analyze Need to plot these point data to clearly view the results You can create your own plotting functions but it is easier to just ‘dump’ the data into a professional plotting software like Excel, Tecplot and even Matlab. The key to ‘dump’ out data is using the fstream library

3 #include #include int main() int main() { fstream data_name fstream data_name data_name.open(“C:/Data/test.dat",ios::out); data_name.open(“C:/Data/test.dat",ios::out); data_name << "VARIABLES = X, Y << endl; data_name << "VARIABLES = X, Y << endl; data_name << "ZONE T=T" << No <<", I=" << (M) << ", J=" << N << ", F=POINT" << endl; data_name << "ZONE T=T" << No <<", I=" << (M) << ", J=" << N << ", F=POINT" << endl; data_name.precision(12); data_name.precision(12); for (int j=1; j<N+1; j++) for (int j=1; j<N+1; j++) { for (int i=1; i<M+1; i++) { for (int i=1; i<M+1; i++) { data_name.width(20); data_name << X[i][j];} { data_name.width(20); data_name << X[i][j];} } return 0; return 0; }

4 Customized Library We have seen that using functions and subroutines defined outside of main to be efficient But having many functions or subroutines within the same main.cpp file can be difficult in terms of managing the size and understanding the main file. What about using subroutines and functions designed by other programmers in your own main file? This is where the use of customized library can be useful

5 How to create a customized library? Can be done by creating another (or many).cpp files Within each.cpp file, you can include the functions and subroutines Since the *.cpp files are outside of main.cpp file, the functions and subroutines are not directly connected to main.cpp How to connect these additional *.cpp files to main.cpp?

6 Using Header file Similar to calling iostream library, you can connect these additional *.cpp files to main.cpp by using a header file and LINK all *.cpp files This header file will include ALL of the initializations of the functions and subroutines in each of the additional *.cpp files. If you are using a GUI-based compiler such as Dev C++, code block or Microsoft C++, you could LINK the *.cpp files by creating a project You need a link.bat to do the same on MS-DOS platform

7 Example Solving a fluid flow over an airfoil In a main function subfunctions or subroutines outside main program BUT still within the same main.cpp file Pseudo-code presentation

8 Functions within main.cpp subroutine geometry and grid modelings subroutine mathematical and physical models Subroutine plot the velocity and pressure fields int main() { preprocessing steps { preprocessing steps …….. …….. loop to solve the problem for pressure and velocities loop to solve the problem for pressure and velocities …….. …….. return 0; return 0; }

9 Problems with all being in main.cpp Main.cpp becomes unnecessarily long and difficult to be understood Not flexible in terms of merging with codes done by other programmers (a standard practice in engineering) Difficult to extend the code for improvements and added capabilities

10 Main function + header file #include #include #include “header_files.h” int main() { preprocessing steps { preprocessing steps loop to solve the problem for pressure &velocities loop to solve the problem for pressure &velocities return 0; return 0; }

11 Header file initializations #include #include #define Pi #define M 60 #define N 60 initializations of geometry and grid modelings subroutines void Cell_Coord(double XCoord[M+2][N+2], double YCoord[M+2][N+2], variables); double YCoord[M+2][N+2], variables); initializations mathematical and physical models subroutines Initializations of plot the velocity and pressure fields functions

12 Geometry.cpp file #include #include # include “header_files.h” //if you need to access other functions outside geometry.cpp void Cell_Coord(double XCoord[M+2][N+2], double YCoord[M+2][N+2], variables) double YCoord[M+2][N+2], variables){ …… ……} void geometry ( ….) {}

13 Kinetic Energy Program #include #include #include “header_files.h” using namespace std; int main() { int n; double KE[n]; double u[n]; double v[n]; double TKE; double TKE; cout << "Enter number of particles: " << endl; cout << "Enter number of particles: " << endl; cin >>n; cin >>n; for (int i=0; i<n; i++) for (int i=0; i<n; i++) { cout << "Enter the u velocity for particles: " << endl; cout << "Enter the u velocity for particles: " << endl; cin >>u[i]; cin >>u[i]; cout << "Enter the v velocity for particles: " << endl; cout << "Enter the v velocity for particles: " << endl; cin >> v[i]; cin >> v[i]; } Determine_KE(n,u,v,KE, TKE); Determine_KE(n,u,v,KE, TKE);getch(); return 0; }

14Header_files.h #include #include #define Pi using namespace std; //initialization of a subroutines to be used in Main or other *.cpp files void Determine_KE(int, double u[], double v[], double KE[], double);

15KE.cpp #include #include #include “header_files.h” using namespace std; //Declaration of a subroutine to be used in Main void Determine_KE(int n, double u[], double v[], double KE[], double TKE) { for (int i=0; i<n; i++) for (int i=0; i<n; i++) { KE[i]= u[i]*u[i] + v[i]*v[i]; KE[i]= u[i]*u[i] + v[i]*v[i]; TKE += KE[i]; TKE += KE[i]; } cout << "TKE is " << TKE << endl; cout << "TKE is " << TKE << endl; }

16 Exercises Repeat Homework #2, but now please include 1. subroutines to compute the second moment of inertia 1. subroutines to compute the second moment of inertia 2. Subroutines to compute the deflection 3. Subroutines to plot the deflection in separate 3 *.cpp files connected within one project using header files.