[Math] Calculating by hand a surface gradient factor.

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

The "gradient factor" a diver is experiencing at any given point of a dive is just the maximum of the percentages of permissible supersaturation across all compartments at that point.

A "Surf GF" is then easy to calculate at any point in time by calculating the ratio of supersaturation to the maximum permissible supersaturation that the diver would experience if they immediately went to 1ATA, for all compartments, and taking the maximum.

(For a deco dive, SurfGF will be higher than GFHi, and probably higher than 100%, at the end of the bottom phase, hence the need tor deco stops on the way up to allow SurfGF to drop. Deco is 'complete' when SurfGF drops below GFHi.)

E.g. the GF the diver is experiencing in column "GF", and SurfGF in the final column on the right under "SGF":
Screen Shot 2022-01-30 at 7.38.29 pm.png

(Don't forget in all of this that compartments, permissible supersaturation etc are all just theoretical concepts that happen to be useful, not actual real things)
 
Everything you are looking for including the calculation of the surface GF is in the Subsurface source code, in particular in subsurface/deco.c at master · subsurface/subsurface and subsurface/profile.c at ecfbf2a9ba51905a6915ba526979130ac134b744 · subsurface/subsurface
In particular, it integrates the differential equation in subsurface/deco.c at ecfbf2a9ba51905a6915ba526979130ac134b744 · subsurface/subsurface
The diffusion constant is ln(2)/half_time with half_time you vary between the different tissues.
 
https://www.shearwater.com/products/teric/

Back
Top Bottom