1!
2!     CalculiX - A 3-dimensional finite element program
3!     Copyright (C) 1998-2021 Guido Dhondt
4!
5!     This program is free software; you can redistribute it and/or
6!     modify it under the terms of the GNU General Public License as
7!     published by the Free Software Foundation(version 2);
8!
9!
10!     This program is distributed in the hope that it will be useful,
11!     but WITHOUT ANY WARRANTY; without even the implied warranty of
12!     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13!     GNU General Public License for more details.
14!
15!     You should have received a copy of the GNU General Public License
16!     along with this program; if not, write to the Free Software
17!     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
18!
19!     this subroutines enables to calculate the critical pressure ratio of a straight
20!     labyrinth seal as a function of the number of spikes (n).
21!
22!     The following table is obtained by solving iteratively the equation :
23!     Ps_inf/Pt0=ppkrit=1/dsqrt(1+2.n-ln(ppkrit))
24!
25!     this equation can be found by using the formula for the ideal mass flow in a straight labyrinth
26!     see "Air system Correlations Part 1 : Labyrith Seals" H.Zimmermann and K.H. Wollf ASME98-GT-206
27!     and determining the maximum flow for a given number of fin.
28!
29!     author: Yannick Muller
30!
31      subroutine lab_straight_ppkrit (n,ppkrit)
32!
33      implicit none
34!
35      integer n
36!
37      real*8 fppkrit(9),ppkrit
38!
39      data fppkrit
40     &     /0.47113022d0,0.37968106d0,0.32930492d0,0.29569704d0,
41     &      0.27105479d0,0.25191791d0,0.23646609d0,0.22363192d0,
42     &      0.21274011d0/
43!
44      ppkrit=fppkrit(n)
45!
46      return
47      end
48