Error in function: too many outputs

This is my function code. I need to call it in my main to use cl and cd. I get the same error that there are too many output arguments. Please help i am lost.

%part a

function [cl,cd] = FlatPlate(alpha,Re)
cl1 = 0.5+(4/30)*log10(Re);
alpha1 = 0.576-(0.192/3)*log10(Re);
alpha2 = alpha1 - 0.0698;
cl2 = 0.7*cl1;
K = 0.75*pi;
cd_max = 1.83;

if Re <= 5e5
    cd0 = 2.656/(sqrt(Re));
elseif (5e5 < Re) && (Re < 5e7)
    cd0 = (0.00375615)+(2.5712025*10^-4)*log10(Re/5e5);
else
    cd0 = 0.148/Re^0.2;
end
cd1 = cd0 + K*alpha2^2;
cd2 = cd1 + 2*K*alpha1*(4*pi/180);
A1 = cd_max/2;
B1 = cd_max;
A2 = (tan(alpha2)/cos(alpha2))*(cl2-cd_max*(0.5)*sin(2*alpha2));
B2 = (cd2 - cd_max*sin(alpha2)^2)/cos(alpha2);
    
    if alpha <= alpha1
        cl = (cl1/alpha1)*alpha;
        cd = cd0+K*(alpha)^2;
    elseif alpha > alpha1
        cl = cl1 + (cl2-cl1)/(alpha2-alpha1)*(alpha-alpha1);
        cd = cd1 +(cd2-cd1)/(alpha2-alpha1)*(alpha-alpha1);
    else
        cl = A1*sin(2*alpha)+A2*((cos(alpha)^2)/(sin(alpha)));
        cd = B1*sin(alpha)^2+B2*cos(alpha);
    end
end 

%HW 5 - MAIN
clear 
clc

c = 3;
B = 4;
rho = 1.2;
visc = 15.2e-6;
V0 = 1.3;
tsr = 2.6;
r = 0.7;
R = 15;
theta = 16;
w = (tsr*V0)/R;
a = 0.0001;
aP = 0;
anew = 0;
aPnew = 0;

x = ((1-a)*V0)/((1+aP)*w*r);
phi = atan(x); %nothing to do w/ geometry 


Vrel = sqrt(((1-anew)*V0)^2+((1+aPnew)*w*r)^2);
Re = (Vrel*c)/visc;
sigma = (B*c)/(2*pi); %solidity

%cl = FlatPlate(alpha, Re);
%cd = FlatPlate(alpha, Re);

[cl, cd] = FlatPlate(alpha, Re);
F = (2/pi)*acos(exp(-(B/2)*((R-r)/(r*sin(phi))))); %tip loss factor
Ct = cl*sin(phi)-cd*cos(phi); % tangential force coeff
Cn = cl*cos(phi)-cd*sin(phi); %axial (normal) force coeff
CT = (sigma*(1-a)^2*Cn)/((sin(phi))^2);
if a<0.3
    anew = 4*a*F*(1-a);
else
    anew = 1/((4*F*(sin(phi))^2)/(sigma*Ct)+1);
end

aPnew = 1/((4*F*sin(phi)*cos(phi))/(sigma*Ct)-1);


disp('The coefficient of thrust is ')
disp(CT)
disp('new a is ')
disp(anew)
disp('new a prime is ')
disp(aPnew)

Answer 1

[Walter Roberson]

You have not defined alpha as a variable, so in your call

[cl, cd] = FlatPlate(alpha, Re);

you are accidentally invoking the function named alpha which happens to not be permitted to have any output arguments.

My guess:

alpha = anew;

and that you want to be calling in a loop to plot a trajectory.

[Lexie Baylor]

So should i put alpha = anew in my main?

[Walter Roberson]

I suspect so. But I do not know what alpha represents in your code and whether it has any relationship to anew. Like is alpha intended to be the "current" version of the variable and anew is intended to be the updated version?

[Lexie Baylor]

Hi, they do not have any correlation together like that. Alpha is a variable that is used to calculate anew.

[Walter Roberson]

Then you should initialize it to whatever value it is intended to have.