Source Code for Module kenozooid.calc

  1  # 
  2  # Kenozooid - dive planning and analysis toolbox. 
  3  # 
  4  # Copyright (C) 2009-2019 by Artur Wroblewski <wrobell@riseup.net> 
  5  # 
  6  # This program is free software: you can redistribute it and/or modify 
  7  # it under the terms of the GNU General Public License as published by 
  8  # the Free Software Foundation, either version 3 of the License, or 
  9  # (at your option) any later version. 
 10  # 
 11  # This program is distributed in the hope that it will be useful, 
 12  # but WITHOUT ANY WARRANTY; without even the implied warranty of 
 13  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 14  # GNU General Public License for more details. 
 15  # 
 16  # You should have received a copy of the GNU General Public License 
 17  # along with this program.  If not, see <http://www.gnu.org/licenses/>. 
 18  # 
 19   
 20  """ 
 21  Functions to calculate 
 22   
 23  - partial pressure 
 24  - equivalent air depth 
 25  - maximum operating depth 
 26  - respiratory minute volume 
 27  """ 
 28   
 29  import functools 
 30   
 31 -def ppg(depth, ean, gas): 
 32      """ 
 33      Calculate partial pressure of a gas. 
 34   
 35      :Parameters: 
 36       depth 
 37          Depth in meters. 
 38       ean 
 39          O2 percentage, i.e. 32, 34, 27.5. 
 40       gas 
 41          Gas name - O2 (oxygen) or N2 (nitrogen). 
 42      """ 
 43      if gas not in ('O2', 'N2'): 
 44          raise ValueError('Invalid gas name: '  + gas) 
 45   
 46      p = 1.0 + depth / 10.0 # absolute pressure 
 47      fg = ean / 100.0 if gas == 'O2' else 1.0 - ean / 100.0 
 48   
 49      return p * fg 
 50   
 51   
 52 -def mod(ean, pp=1.4): 
 53      """ 
 54      Calculate maximum operating depth for a gas and partial pressure. 
 55   
 56      :Parameters: 
 57       ean 
 58          O2 percentage, i.e. 32, 34, 27.5. 
 59       pp 
 60          Partial pressure value. 
 61      """ 
 62      fg = ean / 100.0 
 63      p = pp / fg 
 64      return (p - 1) * 10 
 65   
 66   
 67 -def ead(depth, ean): 
 68      """ 
 69      Calculate equivalent air depth for depth and a gas. 
 70   
 71      :Parameters: 
 72       depth 
 73          Depth in meters. 
 74       ean 
 75          O2 percentage, i.e. 32, 34, 27.5. 
 76      """ 
 77      fN = (100.0 - ean) / 100.0 
 78      return (depth + 10.0) * fN / 0.79 - 10.0 
 79   
 80   
 81 -def rmv(tank, pressure, depth, duration): 
 82      """ 
 83      Calculate respiratory minute volume (RMV). 
 84   
 85      :Parameters: 
 86       tank 
 87          Tank size in liters, i.e. 12l, 15l. 
 88       pressure 
 89          Difference in pressure of the tank at the end and start of a dive, 
 90          i.e. 170 (220 at start, 50 at end of a dive). 
 91       depth 
 92          The average depth of a dive. 
 93       duration 
 94          Duration of a dive in minutes. 
 95      """ 
 96      return tank * pressure / (depth / 10.0 + 1) / duration 
 97   
 98   
 99  pp_n2 = functools.partial(ppg, gas='N2') 
100  pp_n2.__doc__ = """ 
101  Calculate partial pressure of nitrogen. 
102   
103  :Parameters: 
104   depth 
105      Depth in meters. 
106   ean 
107      O2 percentage, i.e. 32, 34, 27.5. 
108  """ 
109   
110  pp_o2 = functools.partial(ppg, gas='O2') 
111  pp_o2.__doc__ = """ 
112  Calculate partial pressure of oxygen. 
113   
114  :Parameters: 
115   depth 
116      Depth in meters. 
117   ean 
118      O2 percentage, i.e. 32, 34, 27.5. 
119  """ 
120   
121  # vim: sw=4:et:ai 
122