MATLAB Answers

harley

iterations while in loop

Asked by harley
on 27 Aug 2013

having trouble making this iterate for each increment of Vn, it goes straight to Vn = 30, i want it to also to calc a new Re, f, dPloss_1, Va & Q with each new iteration.

D = 0.1; L = 10; 
A = 0.25*pi*D^2; 
e = 0.0015e-3; 
rho = 998; 
nu = 1.01e-6;  
eoverD = e/D;
alpha = 0.1;
Vo = 2;
    for Vn = 2:0.1:30;% iteration length. 
    %
    Re = (Vo.*D) / nu;
    % 
    if Re < 2300
    f = 64 / Re;
    else
       darbyFormula = @(x) 1/sqrt(x)+2*log10(eoverD/3.7 + 2.51/Re/sqrt(x));
    f = fzero(darbyFormula,0.01);
    end
    %
    dPloss_1 = (f*rho*(L/D)) * ((Vn*Vo)./2);
    Va = (alpha*Vn)+((1-alpha)*Vo); 
    Q=Va*A;
    Vo = Va;
    end % 

  4 Comments

harley
on 27 Aug 2013

code edited, yes i want it to update at each iteration saving previous values of Re, f, dPloss_1, Va and Q etc.

David Sanchez
on 27 Aug 2013

but what is the problem?

harley
on 27 Aug 2013

David actually works fine, sorry for the confusion.

Products

No products are associated with this question.

1 Answer

Answer by Jan Simon
on 27 Aug 2013
 Accepted answer

No, of course it iterates through 2:0.1:30. You can test this easily either by using the debugger or by a disp(Vn) command inside the loop.

The problem might be, that the result is overwritten in each iteration. So try:

Vn_pool = 2:0.1:30;
Q = zeros(1, length(Vn_pool)));  % pre-allocate!!!
for k = 1:length(Vn_pool)
  Vn = Vn_pool(k);
  ...
  Q(k) = Va * A;  % same for the other values wanted as outputs
end

  1 Comment

harley
on 27 Aug 2013

yes your right, its over writing each iteration, thanks.


Discover what MATLAB® can do for your career.

Opportunities for recent engineering grads.

Apply today