MATLAB: Trouble with ODE45 for an array of values

arraydifferential equationsode45plots

Hi,
I have an equation udC/dx=R, where C and R are arrays. I've written a code but its giving a linear plot. Need help
% Solve ODE for Multi-Species Isothermally
% Constants
u = 1.5;
A  = 2.2e10;
Ea = 130;
Ru = 8.3145;
T  = 750;
L  = 0.12;
N  = 39;
% Initial Conditions
Cco(1)   = 0.52; 
Co2(1)  = 0.99; 
Ch2o(1)  = 0; 
delx  = L/(N-1);
x     = 0:delx:0.12;
C0    = [Cco(1) Co2(1) Ch2o(1)];
C     = zeros(3,1);
Rco   = -A * (exp(-Ea / (Ru*T))) * Cco * sqrt(Co2); 
Ro2   = 0.5 * Rco;  
Rh2o  = -Rco;       
dC    = [Rco Ro2 Rh2o] / u;
R     = [Rco Ro2 Rh2o];
R     = zeros(3,1);
% ODE45 solver
[x,C] = ode45(@(x,C) R/u, x, C0);
plot(x,C,'-+')
title('Molar Concentration vs. Distance');
legend('CO','O2','CO2');
xlabel('Axial(x) Direction [m]');
ylabel('Concentrations [mol/m3]');
Thank you.

Best Answer

% Solution 4: Chemical Species Concentration as a Function of Axial Distance
clc
clear
% Constants

L  = 0.12;
N  = 39;
T(1:N) = 750;
delx     = L/(N-1);
xspan    = 0:delx:0.12;
C0       = [0.52 0.99 0.0];
% ODE 45 Code
[x,C]=ode45('hw2_4',xspan,C0);
% Plots
subplot(2,1,1);
plot(x,C(:,1),'b--o',x,C(:,2),'g--+',x,C(:,3),'r--s')
legend('C_{CO}','C_{O2}','C_{CO2}')
xlabel('Axial (x) Direction [m]')
ylabel('Concentrations [mol/m^3]')
title('Molar Concentration vs Distance')
Function File:
function dcdx=hw2_4(x,C)
% Constants
u = 1.5;
A  = 2.2e10;
Ea = 130000;
Ru = 8.3145;
T  = 750;
% Rate Constants
R(1)     = -A * (exp(-Ea / (Ru*T))) * C(1) * sqrt(C(2)); 
R(2)     = 0.5 * R(1);  
R(3)     = -R(1);
dcdx     = [R(1);R(2);R(3)]/u;
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