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