Code for equation with ln

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Sayeed 2018-10-21

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/425183-code-for-equation-with-ln

评论： Star Strider 2018-10-21

NP.png

How can i Code it?

u=0.23 y=0.3 v=0.00001

u/u’=5*log(u’*y/v)-3.05

u’=?

I need to find the value of u’.

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Star Strider 2018-10-21

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/425183-code-for-equation-with-ln#answer_342499

在 MATLAB Online 中打开

Try this:

u=0.23; 
y=0.3; 
v=0.00001;
fcn = @(ustar,u,y,nu) 5*log(ustar.*y/nu)- 3.05 - u/ustar;
ustar = fsolve(@(ustar)fcn(ustar,u,y,v), 1)
ustar =
       0.00918407730971717

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Sayeed 2018-10-21

It is somehow not working to my matlab. Can you please send me the code file with attachment?

Star Strider 2018-10-21

在 MATLAB Online 中打开

I already posted all the code that is needed to solve this problem.

You need to have the Optimization Toolbox installed to use fsolve.

You will have fminsearch regardless, so try using fminsearch on the norm of ‘fcn’:

ustar = fminsearch(@(ustar)norm(fcn(ustar,u,y,v)), 1)
ustar =
             0.00918426513671787

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Mathematics and Optimization Optimization Toolbox Systems of Nonlinear Equations Newton-Raphson Method

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