evaluation a drag over a pre-designed model of a car using CFD

https://docs.google.com/document/d/1Nc89Y_wGmIrIAlx5-fdcgDCSJWuoJGJypjjsSJsr4u8/edit?usp=sharing

clear all
close all
clc

%defining all the constant values       
L = 1;  
n = 161;
c = 1;
dt = 0.01;

%calculation 
x = linspace(0,L,n);
dx = L/(n-1);

x_start = find(x==0.1); 
x_stop = find(x==0.3);

%initialize arrays and apply boundary conditions 
u = ones(1,n);
u(1) = 1;
u(x_start:x_stop) = 2;
uold = u;
u_initial = u;
nt = 40;
%time loop 
for k = 1:nt
    %space loop
    for i=2:n
    u(i)=uold(i)-(((c*dt)/dx)*(uold(i)-uold(i-1)));
    end
    uold = u;
    
end 
    plot(x,u_initial,\'b\');
    hold on 
    plot(x,u,\'r\');