diff options
Diffstat (limited to 'deco.c')
| -rw-r--r-- | deco.c | 30 |
1 files changed, 26 insertions, 4 deletions
@@ -115,7 +115,28 @@ const double buehlmann_He_factor_expositon_one_second[] = { const double conservatism_lvls[] = { 1.0, 1.05, 1.12, 1.22, 1.35 }; -#define WV_PRESSURE 0.0627 // water vapor pressure in bar +/* Inspired gas loading equations depend on the partial pressure of inert gas in the alveolar. + * P_alv = (P_amb - P_H2O + (1 - Rq) / Rq * P_CO2) * f + * where: + * P_alv alveolar partial pressure of inert gas + * P_amb ambient pressure + * P_H2O water vapour partial pressure = ~0.0627 bar + * P_CO2 carbon dioxide partial pressure = ~0.0534 bar + * Rq respiratory quotient (O2 consumption / CO2 production) + * f fraction of inert gas + * + * In our calculations, we simplify this to use an effective water vapour pressure + * WV = P_H20 - (1 - Rq) / Rq * P_CO2 + * + * Buhlmann ignored the contribution of CO2 (i.e. Rq = 1.0), whereas Schreiner adopted Rq = 0.8. + * WV_Buhlmann = PP_H2O = 0.0627 bar + * WV_Schreiner = 0.0627 - (1 - 0.8) / Rq * 0.0534 = 0.0493 bar + + * Buhlmann calculations use the Buhlmann value, VPM-B calculations use the Schreiner value. +*/ +#define WV_PRESSURE 0.0627 // water vapor pressure in bar, based on respiratory quotient Rq = 1.0 (Buhlmann value) +#define WV_PRESSURE_SCHREINER 0.0493 // water vapor pressure in bar, based on respiratory quotient Rq = 0.8 (Schreiner value) + #define DECO_STOPS_MULTIPLIER_MM 3000.0 #define NITROGEN_FRACTION 0.79 @@ -270,7 +291,7 @@ double he_factor(int period_in_seconds, int ci) double calc_surface_phase(double surface_pressure, double he_pressure, double n2_pressure, double he_time_constant, double n2_time_constant) { - double inspired_n2 = (surface_pressure - WV_PRESSURE) * NITROGEN_FRACTION; + double inspired_n2 = (surface_pressure - ((in_planner() && (prefs.deco_mode == VPMB)) ? WV_PRESSURE_SCHREINER : WV_PRESSURE)) * NITROGEN_FRACTION; if (n2_pressure > inspired_n2) return (he_pressure / he_time_constant + (n2_pressure - inspired_n2) / n2_time_constant) / (he_pressure + n2_pressure - inspired_n2); @@ -468,7 +489,8 @@ double add_segment(double pressure, const struct gasmix *gasmix, int period_in_s int ci; struct gas_pressures pressures; - fill_pressures(&pressures, pressure - WV_PRESSURE, gasmix, (double) ccpo2 / 1000.0, dive->dc.divemode); + fill_pressures(&pressures, pressure - ((in_planner() && (prefs.deco_mode == VPMB)) ? WV_PRESSURE_SCHREINER : WV_PRESSURE), + gasmix, (double) ccpo2 / 1000.0, dive->dc.divemode); if (buehlmann_config.gf_low_at_maxdepth && pressure > gf_low_pressure_this_dive) gf_low_pressure_this_dive = pressure; @@ -504,7 +526,7 @@ void clear_deco(double surface_pressure) { int ci; for (ci = 0; ci < 16; ci++) { - tissue_n2_sat[ci] = (surface_pressure - WV_PRESSURE) * N2_IN_AIR / 1000; + tissue_n2_sat[ci] = (surface_pressure - ((in_planner() && (prefs.deco_mode == VPMB)) ? WV_PRESSURE_SCHREINER : WV_PRESSURE)) * N2_IN_AIR / 1000; tissue_he_sat[ci] = 0.0; max_n2_crushing_pressure[ci] = 0.0; max_he_crushing_pressure[ci] = 0.0; |