How could I make a script for this ecuation where i can solve for f?

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Jorge 2024-11-20，21:39

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https://ww2.mathworks.cn/matlabcentral/answers/2167603-how-could-i-make-a-script-for-this-ecuation-where-i-can-solve-for-f

评论： Torsten 2024-11-20，23:43

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Walter Roberson 2024-11-20，23:19

编辑：Walter Roberson 2024-11-20，23:20

在 MATLAB Online 中打开

rng(655321)
epsilon = rand
epsilon = 0.3140
D = rand
D = 0.3864
Re = rand
Re = 0.1855
eqn = @(x) x + 2*log10(epsilon/D/3.7+2.51*x/Re);
X = fzero(eqn, [0 1e5])
X = 0.0533

Torsten 2024-11-20，23:43

在 MATLAB Online 中打开

...  
f = 1/X^2

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回答（1 个）

Walter Roberson 2024-11-20，22:05

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https://ww2.mathworks.cn/matlabcentral/answers/2167603-how-could-i-make-a-script-for-this-ecuation-where-i-can-solve-for-f#answer_1547558

编辑：Walter Roberson 2024-11-20，23:23

在 MATLAB Online 中打开

syms f epsilon D Re
Q = @(v) sym(v);
eqn = 1/sqrt(f) == -Q(2.0) * log(epsilon/D/Q(3.7) + Q(2.51)/(Re*sqrt(f)))
F = solve(eqn, f)
Warning: Solutions are only valid under certain conditions. To include parameters and conditions in the solution, specify the 'ReturnConditions' value as 'true'.
disp(char(F))
(86248369*D^2)/(1000*Re*epsilon - 18574*wrightOmega((500*Re*epsilon)/(9287*D) - log(251/(50*Re)))*D)^2

wrightOmega is a function in the Symbolic Toolbox

rng(655321)
epsilon = rand
epsilon = 0.3140
D = rand
D = 0.3864
Re = rand
Re = 0.1855
f = subs(F)
disp(char(vpa(f)))
322.8497917132456879511724468922
subs(eqn)
disp(char(vpa(ans)))
0.055654430712142653567619972363646 == 0.055654430712142653567619972363646