VPM Program Settings

	VPM Program Settings for the BASIC and VBA versions Copyright 1999 by Eric Maiken


Units and Constants The calculations were done in pressure units of "Atmospheres," with 1 atm ~ 1 bar~ 10⁵ Pascals. So when you see a "33" in the code, this is a conversion of units: 1 atm = 33 feet of salt water. Note: 33 feet of saltwater = 34 feet of fresh water. 3.3 feet of anything = 1 meter. The partial pressures of water vapor and carbon dioxide, set as ppH₂OCO₂ = 102 / 760 in SUB DIVEDATA, are subtracted from ambient pressure before partial pressures of nitrogen and oxygen are calculated. The starting pressure is set as 1 ata. VPM Constants The constants r_o, gamma, and *lambda* are set in SUB diveData. As *r_o* increases, psMin and criticalGradient get smaller, leading to longer decompression times. Substitution of the range of values 0.8 < r_o< 1.2 into the code is physically reasonable. As gamma (= g in Refs. 1 and 2 ) decreases, psMin and criticalGradient get smaller, leading to longer decompression times. Substitution of the range 16 < gamma < 20 into the code is physically reasonable. My Programs' Constants The default half-times are Buhlmann's ZHL-16 set: 4.,8.,12.5,18.5,27.,38.3,64.3,77.,109.,146.,187.,239.,305.,390.,498.,635. (min) The VPM constants are the same as Yount and Hoffman's. *r_o* = 1 (micron) *gamma* = 17.9 (dyne/cm) lambda = 7180 (fsw min) Yount and Hoffman's Constants The eight fastest half-times in ref 1 are: 2,5,10,20,40,80,120,160 (min). Lambda: l = 7500 (ffw min) *r_o* = 1 (micron) Wienke's Constants Half-times in ref 2 are: 1,2,5,10,20,40,80,120,180,240,360,480,720 (min). Delta = d --same as Yount's lambda: l-- 7180 (fsw min) = 7502 (feet of freshwater x minutes) *r_o* = 0.8 (micron)