Code for equation with ln

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Sayeed
Sayeed 2018-10-21
评论： Star Strider 2018-10-21

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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回答（1 个）

Star Strider
Star Strider 2018-10-21
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
  2 个评论
Sayeed
Sayeed 2018-10-21
It is somehow not working to my matlab. Can you please send me the code file with attachment?
Star Strider
Star Strider 2018-10-21
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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