Alternative form of Reynold's number

  • Thread starter foo9008
  • Start date
  • #1
678
4

Homework Statement


in the third picture , we know that π2 can be written as function of π1 , where π2 is inverse of reynold number , how if i want to change it to π1 = function of π2 , can i write it as (Reynold number ) = F / ρ (D^2)(v^2) ???

p/s : π1 is actually inverse of reynold number

Homework Equations




The Attempt at a Solution


IMO , for π1 = function of π2 , it is also (Reynold number ) = f (F / ρ (D^2)(v^2) ) ... we should write it as reynold number instead of inverse of reynold number , am i right ?
 

Attachments

Answers and Replies

  • #2
821
192
What does upper case phi double prime stand for?

Φ'' (Re) = FD/ρD2V2
 
  • #3
678
4
What does upper case phi double prime stand for?

Φ'' (Re) = FD/ρD2V2
I think the author means stand for function.......
 
  • #4
678
4
What does upper case phi double prime stand for?

Φ'' (Re) = FD/ρD2V2
do u have any idea now ?
 
  • #5
678
4
anyone know the answer?
 
  • #6
821
192
OK. If Φ represents a function then double prime would normally indicate the second derivative of that function.
 
  • #7
678
4
OK. If Φ represents a function then double prime would normally indicate the second derivative of that function.
can i write it as (Reynold number ) = F / ρ (D^2)(v^2) ???

or , it should be 1/ reynold number = F / ρ (D^2)(v^2) ???
which one is correct ?
 
  • #8
821
192
1/Re = F/ρD2V2

where F = viscous forces
 
  • #9
678
4
1/Re = F/ρD2V2

where F = viscous forces
is it wrong to write it as (Reynold number ) = F / ρ (D^2)(v^2) ???
is there a need to change 1/ Re to Re for π1 in this case
P/s : π1 = function of ( π2 , π3 )
 
  • #10
821
192
The Reynolds number is dimensionless, so the numerator and denominator will have the same fundamental dimensions (M, L, T).

In aeronautics, the denominator (viscous forces) is smaller than the numerator (inertial forces) -- possibly 5 or 6 orders of magnitude smaller -- which makes Re a large number.
 
  • Like
Likes foo9008
  • #11
678
4
The Reynolds number is dimensionless, so the numerator and denominator will have the same fundamental dimensions (M, L, T).

In aeronautics, the denominator (viscous forces) is smaller than the numerator (inertial forces) -- possibly 5 or 6 orders of magnitude smaller -- which makes Re a large number.
So, no matter pi 1 is Reynold number = ( pi 2 , pi3) or pi 1 is 1/ reynold number d= ( pi2, pi3) are correct??
 
  • #12
821
192
2 = FD/ρD2V2

What do ∏1 and ∏3 equal?
 

Related Threads on Alternative form of Reynold's number

  • Last Post
Replies
3
Views
587
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
7
Views
677
  • Last Post
Replies
1
Views
762
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
1
Views
4K
Replies
4
Views
9K
Replies
8
Views
8K
Replies
1
Views
424
Replies
3
Views
7K
Top