Matlab unrecognized function or variable

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Fatih Güler
Fatih Güler 2020-12-13
评论： Walter Roberson 2020-12-13
p=1.23;
D=.005;
V=40;
mu=1.7910^-5;
e=.0015;
Re=pVD/mu;%reynolds number equation
f=@(x)(1/sqrt(x)+2log(e/(3.7D)+2.51/(Resqrt(x))));
a=.008;
b=.08;
while abs(b-a)>1e-9
c=(a+b)/2;
if f(a)*f(c)<0
b=c;
else
a=c;
end
end
fprintf('Root found: %.10f\n',c)
fprintf('Function value at root %E\n',f(c))

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采纳的回答

Ive J
Ive J 2020-12-13
Correct these two lines
Re=p*V*D/mu;%reynolds number equation
f=@(x)(1/sqrt(x)+2*log(e/(3.7*D)+2.51/(Re*sqrt(x))));

更多回答（1 个）

Walter Roberson
Walter Roberson 2020-12-13
MATLAB has absolutely no implied multiplication. If you want p multiplied by V multiplied by D then you need p*V*D not pVD .
... otherwise if you had an m and a u variable, how would it know whether that division by mu was division by the variable mu or division by (m * u) or division by m and then multiplication by u ?

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