Function returns a vector of length 6, but the length of initial conditions vector is 34. The vector returned by ICEMODELFUNC and the initial conditions vector must have the same number of elements.

% Flat Terrain
thetaDEG = 0:45:315;  % Degrees
thetaRAD = deg2rad(thetaDEG); % Radians
r = 55;               % Meters
m = 0.5;              % kg
rhoice = 900;         % kg/m^3 (hard rime or glaze)
omegaRPM = 14.5;      % rpm
omega = 1.5184364475; % rad/s
Cd = 1;
rhoair = 1.25;        % kg/m^3
u = 100;              % Meters
l = (m/rhoice)^(1/3);
A = l^2;              % m^2
% A = 0.0135;           % m^2 - Assumed to be a CUBE shape
Z0 = 0.01;            % Meters - Roughness Length
Zh = 125;             % Meters - Hub Height
U = 10;               % m/s - Velocity at U
g = 9.81;             % m/s

% Time
tdelta = 0.2; % seconds
t0 = 0;       % seconds
tf = 10; % seconds
t = t0:tdelta:tf;        

% Turbine Location
x = 0;
y = 0;
z = 0;
pos = [x,y,z];

% Aerodynamic Drag

Fd = -Cd*rhoair*A*U^2;

for i = 1:length(thetaRAD)

x1 = 0; % x0
x2 = 0; % Vx0
x3(i) = r*cos(thetaRAD(i)); % y0
x4(i) = -r*omega*sin(thetaRAD(i)); % Vy0
x5(i) = r*sin(thetaRAD(i)); % z0
x6(i) = r*omega*cos(thetaRAD(i)); % Vz0

end

% ODE Function
initial = [x1,x2,x3,x4,x5,x6];
tspan = t0:tdelta:tf;
[t,x] = ode45(@IceModelFunc, tspan, initial);

plot(x(1),x(3))
grid on
grid minor

---------------------------------------MY FUNCTION IS BELOW---------------------------------------------

function funcxyz = IceModelFunc(t,x)
m = 0.5;
rhoair = 1.25;
Cd = 1;
A = 0.0068;
U = 10;
g = 9.81;

% x = x1;
% xd = x2;
% y = x3;
% yd = x4;
% z = x5;
% zd = x6;

funcxyz = zeros(6,1);
funcxyz(1) = x(2);
funcxyz(2) = -(1/(2*m))*rhoair*Cd*A*(x(2)-U)*sqrt((x(2)-U)^2*x(4)^2*x(6)^2);
funcxyz(3) = x(4);
funcxyz(4) = -(1/(2*m))*rhoair*Cd*A*x(4)*sqrt((x(2)-U)^2*x(4)^2*x(6)^2);
funcxyz(5) = x(6); 
funcxyz(6) = -g - (1/(2*m))*rhoair*Cd*A*(x(5))*sqrt((x(2)-U)^2*x(4)^2*x(6)^2);
end

[darova]

Can you be more specific? Are you trying to compute several solutions?

[AeroEng]

Yes, So I am trying to perform multiple iterations in order to plot distance along the x-direction (which is x(1)) vs distance along the y-direction (which is x(3)) all with different values of theta. I have 8 values for theta and I want to plot all 8 of those values. So yes I have multiple iterations. However the output of the function gives me an vector length of 6 (x(1), x(2), ... x(6)) and my for loop gives me an output for 8 theta values but for all 6 (first two being equal to zero so those are a single value) values so I end up with 34 as a length for the vector out of my for loop. I need to somehow make those equal so I can plot this. I should end up with 8 lines in my plot at the end but I dont get anything due to this issue. Let me know if there is any more confusion I will clear it up. THANK YOU SO MUCH!

[AeroEng]

Also just to let you know:

x(1) = Position in x-direction - x

x(2) = Velocity in x-direction - x_dot or dx/dt

x(3) = Position in y-direction - y

x(4) = Velocity in y-direction - y_dot or dy/dt

x(5) = Position in z-direction - z

x(6) = Velocity in z-direction - z_dot or dz/dt

Answer 1

[darova]

You want several solution for thetaRAD

So just put your ode45 function inside for loop

tspan = t0:tdelta:tf;
for i = 1:length(thetaRAD)
    x1 = 0; % x0
    x2 = 0; % Vx0
    x3 = r*cos(thetaRAD(i)); % y0
    x4 = -r*omega*sin(thetaRAD(i)); % Vy0
    x5 = r*sin(thetaRAD(i)); % z0
    x6 = r*omega*cos(thetaRAD(i)); % Vz0
    % ODE Function
    initial = [x1,x2,x3,x4,x5,x6];
    [t,x] = ode45(@IceModelFunc, tspan, initial);
    figure(i)
    title(sprintf('theta: %d',thetaDEG(i)))
    line(t,x)
end

[AeroEng]

Even while doing that I continue to get this error message:

Error using odearguments (line 95)
ICEMODELFUNC returns a vector of length 6, but the
length of initial conditions vector is 42. The
vector returned by ICEMODELFUNC and the initial
conditions vector must have the same number of
elements.

Error in ode45 (line 115)
  odearguments(FcnHandlesUsed, solver_name, ode,
  tspan, y0, options, varargin);

Error in FragmentThrow (line 62)
[t,xx] = ode45(@IceModelFunc, tspan, initial);

[darova]

Can you show the whole code?

[AeroEng]

I did above. The only thing I kept out was my name and partners names for privacy. If it helps the clc; starts on line 6 in my code. In my function, the "Function" starts on line 4. I attached it again below. Thank you very much!

clc;
clear;
close all;

% Initial Conditions

% Flat Terrain
thetaDEG = 0:45:315;  % Degrees
thetaRAD = deg2rad(thetaDEG); % Radians
r = 0:5:45;               % Meters
m = 0.5;              % kg
rhoice = 900;         % kg/m^3 (hard rime or glaze)
omegaRPM = 14.5;      % rpm
omega = 1.5184364475; % rad/s
Cd = 1;
rhoair = 1.25;        % kg/m^3
u = 100;              % Meters
l = (m/rhoice)^(1/3);
A = l^2;              % m^2
% A = 0.0135;           % m^2 - Assumed to be a CUBE shape
Z0 = 0.01;            % Meters - Roughness Length
Zh = 125;             % Meters - Hub Height
U = 10;               % m/s - Velocity at U
g = 9.81;             % m/s

% Time
tdelta = 0.2; % seconds
t0 = 0;       % seconds
tf = 10; % seconds
t = t0:tdelta:tf;        

% Turbine Location
x = 0;
y = 0;
z = 0;
pos = [x,y,z];

% Aerodynamic Drag

Fd = -Cd*rhoair*A*U^2;

% thetaRAD = deg2rad(45);


for i = 1:length(thetaRAD)

            x1 = 0; % x0
            x2 = 0; % Vx0
            x3 = r*cos(thetaRAD(i)); % y0
            x4 = -r*omega*sin(thetaRAD(i)); % Vy0
            x5 = r*sin(thetaRAD(i)); % z0
            x6 = r*omega*cos(thetaRAD(i)); % Vz0

            % ODE Function
initial = [x1,x2,x3,x4,x5,x6];
tspan = t0:tdelta:tf;
[t,xx] = ode45(@IceModelFunc, tspan, initial);
figure(i)
line(t,xx)
end
    



plot(xx(:,1),xx(:,3))
grid on
grid minor

My Function is shown Below

function func1 = myfuncx(t,x1,x2,x3,x4,x5,x6)
m = 0.5;
rhoair = 1.25;
Cd = 1;
A = 0.0068;
U = 10;

x = x1;
xd = x2;
y = x3;
yd = x4;
z = x5;
zd = x6;


func1 = zeros(6,6);
func1(1) = x2;
func1(2) = -(1/(2*m))*rhoair*Cd*A*(x2-U)*sqrt((x2-U)^2*x4^2*x5^2);
func1(3) = x4;
func1(4) = -(1/(2*m))*rhoair*Cd*A*x4*sqrt((x2-U)^2*x4^2*x5^2);
func1(5) = x5; 
func1(6) = -(1/(2*m))*m*g - 0.5*rhoair*Cd*A*(x5)*sqrt((x2-U)^2*x4^2*x5^2);
end

[darova]

Your first ode function was correct. This is not

[AeroEng]

How do you mean. I only see a few differences that when i fixed them, it didnt change the outcome. I forgot to comment out the x=x1;xd=x2;...etc. Did that and didnt change it. Also i changed the xx from the ode back to a single x. Lastly I changes the zeros(6,6) back to zeros(6,1). None of that fixed it. What am I missing?

[darova]

I mean declaration

If you want to use x1 instead of x(1) declare them inside your function

function func1 = myfuncx(t,x1,x2,x3,x4,x5,x6)
m = 0.5;
rhoair = 1.25;
Cd = 1;
A = 0.0068;
U = 10;
x1 = x(1);
x2 = x(2);
% ...