# Buckingham theorem

1. Jun 1, 2016

### welovephysics

1. The problem statement, all variables and given/known data
why there is a need to change π3 to π3 ' (which is inverse of reynold number)???? (in 2nd picture)

2. Relevant equations

3. The attempt at a solution
why can we do so ? i was told that π1 = f( π2 , π3 , .......)
if we use π3' , which is this will change the original meaning of π1 = f( π2 , π3 , .......) , am i right ? IMO, this is wrong , there's no need to change π1 = f( π2 , π3 , .......) 3 to π1 = f( π2 , π3 , .......) 3 ' ...
can someone explain on it ?

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2. Jun 2, 2016

### haruspex

If π1 is a function of π2 and π3 then it is also true that it is a function of π2 and π3-1. It's just a different function.
Until you have locked in how f is defined, you are free to choose how to define it.
That said, I don't see the advantage here in switching from π3 to π3-1.