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what is the function of the while loop in this code

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Ghaith Abdul
Ghaith Abdul 2018-3-27
关闭： MATLAB Answer Bot 2021-8-20
Please explain why is the while loop using the -0.00001>c< etc and the else
function [ output_args ] = Reynoldsnumber( input_args )
D = .01;
v = [0 25 50 75 100 125 150];
WV= .0000008917;
e = .00006096;
RR = e/D;
p = 997.04;
F1 = 1;
F2 = 2;
c = 3;
Rey1 = (p.*v.*D)./WV;
while -0.00000001>c<0.00000001
if -0.00000001>c
F2=(-2.*log10(RR/3.7+(2.57./(Rey1.*sqrt(F1))))).^(-2);
F1=F1+.001;
c=F2-F1;
else
F2=(-2.*log10(RR/3.7+(2.57./(Rey1.*sqrt(F1))))).^(-2);
F1=F1-.001;
c=F2-F1;
end
end
semilogx(Rey1,F2)
disp(Rey1)
if true
% code
end
end

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回答（1 个）

Bob Thompson
Bob Thompson 2018-3-27
1) I'm pretty sure that MATLAB logic doesn't work for that while condition. It should be:
while -0.00001>c || c<0.000001;
Also, the logic statement itself doesn't make sense, as any negative number fulfills both conditions, so I assume it's supposed to be c > 0.00001.
2) The while loop is used to iteratively solve for F2. c is initially specified outside of the ending conditions, which is not true here, and is recalculated as the difference of F2 and F1 each loop until the difference between the two F values is small enough to be acceptable.
  2 个评论
Ghaith Abdul
Ghaith Abdul 2018-3-27
Unforutnelly I tried what you wrote and the graph comes up empty. The professor said it is the right way and it is correct. But I need to figure out the function of it and why is it that way for the presentation and I am coming up empty
Bob Thompson
Bob Thompson 2018-3-27
Whether or not the code specifics are correct, that is definitely an iteration loop.

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