Error using vertcat Dimensions of arrays being concatenated are not consistent.

I understand that this code returns a vector length of 303 but the initail vector (y0) only contains 3. I am not sure how to fix this error.

Vspan = [0 10];
y0 = [0 570 (50*101.325)];
[V,y] = ode45(@(~,y) fun(del_h1,del_cp1,cp1),Vspan,y0);

function dydt = fun(~,y,del_h1,del_cp1,cp1)

X = y(1);
T = y(2);
P = y(3);

% inital parameters 
T0 = 570;  % [K]  inlet temp
P0 = 50*101325;  % [Pa]  inlet pressure
Ft0 = 8000;  % inlet total flow rate w mixture [kmol/hr]
%T = 570:2.3:800;  % 800 is max temp allowed [K]
Ac = 3;  % cross sectional area [m^3]
R = 8.314*1000;  % [J/kmol.K]
%X= 0:.01:1;
%T = T';

%X = X';

% mol fractions
  % let 1 = H2, 2 = CO, 3 = CH4, 4 = H2O
  % 5 = CO2, 6 = C2H4, 7 = N2
y10 = 0.555; y20 = 0.215; y30 = 0.167; 
y50 = 0.033; y60 = 0.019; y70 = 0.011;  % inert gases

% molar masses [kg/kmol]
m1 = 2.016; m2 = 28.01; m3 = 16.04; m4 = 18.016; m5 = 44.01;
m6 = 30.07; m7 = 28.02;

% finding density of gas mixture  (not sure if this is right way lol)
  % should inert gases be included?
  % found this at https://chemistry.stackexchange.com/questions/91120/finding-density-of-the-gas-mixture
mt = y10*m1 + y20*m2 +y30*m3 + y50*m5 + y60*m6 + y70*m7;  % total mass  [kg/kmol]
yt = y10 + y20 + y30 + y50 + y60 + y70;  % total mole fraction
rho = (P.*mt)./(yt.*R.*T);  % density of mixture

% flow rates [kmol/hr]
F10 = Ft0*y10;  F20 = Ft0*y20; F30 = Ft0*y30;

% thetas
theta_b = F20/F10; theta_c = F30/F10; 

% flow rates  [kmol/hr]
delta = -2/3;
F1 = F10.*(1-X);
F2 = F10.*(theta_b - (X./3));
F3 = F10.*(theta_c + (X./3));
F4 = (F10.*X)/3;
Ft = Ft0 + delta.*F10.*X;

% masses

% finding concentrations
   % note that: density = (molar flow)/(volumetric flow)
E = y10*delta;
vo = Ft0/Ac;  % not the right volumetric flow rate
v = vo*(1+E.*X).*(T./T0).*(P0./P);  % volumetric flow rate
C1 = F1./v; C2 = F2./v; C3 = F3./v; C4 = F4./v;

 % let 1 = H2, 2 = CO, 3 = CH4, 4 = H2O, 5 = CO2, 6 = C2H4, 7 = N2
% parameters
a = [28.84 28.95 34.31 33.46 36.11 49.37 29]/10^3;
b = [.00765 .411 5.469 .688 4.233 13.92 .2199]/10^5;
c = [.3288 .3548 .3661 .7604 -2.887 -5.816 .5723]/10^8;
d = [-.8698 -2.22 -11 -3.593 7.464 7.28 -2.871]/10^12;
a = a';
b = b';
c = c';
d = d';

rho_cat = (1.14*(100^3))/1000;  % [kg/m^3] catalyst density
D = ((2.81E-06).*T + 1.68E-04)/(100^2);  % [m^2/s] effective diffusivity
area = 150*1000;  % [m^2/kg.catalyst]
volume = (0.395*1000)/(100^3);  % pore volume [m^3/kg]
UaTaT = 0;  % this is U*a*(Ta-T) which is neglible

% arrhenius equation
A = [0.2687 9.706E-12 4.124E-09]/1000;  % [in Pascal]  
Ea = [70 -90 -68.5]*1000;  % [kPa] may need to multiply by 1000 to get into Pa
K0 = A(1)*exp(-Ea(1)./(R.*T));
K1 = A(2)*exp(-Ea(2)./(R.*T));
K2 = A(3)*exp(-Ea(3)./(R.*T));

  % partial pressures
P1 = P.*y10;  
P2 = P.*y20;

r1 = -( (K0.*P1) ./ ( (1+sqrt(K1.*P1)+(K2.*P2)).^2) );
r1_prime = r1/rho_cat;

% effectiveness factor

tmod = 0.16.*sqrt(1./((2.81E-06).*T + 1.68E-04));
n = (3.*(tmod.*cot(tmod) - 1))./(tmod.^2);  % effectiveness factor


% Erguen equation stuff
y = P./P0;
U = v./Ac;
phi = 0.4;
gc = 1;  % for metric system
Dp = 0.32/100;  % [m] particle diameter
G = rho_cat.*U;
u = 3.2*10^-4;  % viscosity
Bo = ((G.*(1-phi))./(rho_cat.*gc.*Dp.*(phi.^3))).*(((150.*(1-phi)*u)./Dp) + 1.75.*G);
gamma = (2.*Bo)./(Ac.*rho_cat.*(1-phi).*P0);

    dydt = [ -r1_prime.*n./F10;  % dXdW
        (1./rho_cat).*( (UaTaT + n.*r1_prime.*del_h1) ./ (F10.*(cp1+ del_cp1.*X)) );  % dTdW
        (-gamma./(2.*y)).*(T./T0).*(1+E.*X) ];% dydW
    %dydt = dydt';


end

Answer 1

[James Tursa]

You have a mismatch in the number of arguments. E.g., this

[V,y] = ode45(@(~,y) fun(del_h1,del_cp1,cp1),Vspan,y0);

should be this

[V,y] = ode45(@(t,y) fun(t,y,del_h1,del_cp1,cp1),Vspan,y0);

[Cesar Rubio]

I now get an error saying

Unrecognized function or variable 'del_h1'.

but I have 'del_h1' within my for loop. Why does MATLAB say that it is not defined?

[James Tursa]

I had assumed there was other code in front of this defining these variables that you weren't showing. You need to define all input arguments used in a function handle prior to creating the function handle. The t and y come from ode45. But you must define del_h1, del_cp1, and cp1 prior to creating the function handle that uses them. Although this is itself confusing in your code since you seem to redefine these variables inside your derivative function. Which is it? Are you wanting to pass these in as input arguments, or define them inside the derivative function?

[Cesar Rubio]

I want to pass them as input arguments into the function, but even with your suggested input I still recieve the follwoing error.

Error using vertcat
Dimensions of arrays being concatenated are not consistent.

[Cesar Rubio]

I am thinking the error has something to deal with the 'dydt' having a much longer vector length than 'y0' but I do not know how to fix this. My goal is to solve the ODE's for a many ranges of cp1, del_cp1, and del_h1 values.

[James Tursa]

Please post your current code.