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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 %

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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

## 4 Comments

## David Sanchez (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/85684#comment_166049

what is the problem? Who is

D? Do you want to update Re, f, dPloss_1, Va and Q, saving previous values?## harley (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/85684#comment_166050

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 (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/85684#comment_166051

but what is the problem?

## harley (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/85684#comment_166053

David actually works fine, sorry for the confusion.