Help me understand how deco stops are calculated.

[hammet]

Thanks @KWS for the response. I know you typed a lot, so I appreciate the effort. I do understand the concept that your saying. My question meant to be a little more specific of how the computer or software program manages the calculation...I don't mean the exact program code, but the mathematics and equations that one could program into a computer to ascertain the theoretical saturation of each compartment as a function of depth and time. I think I may have found the answer in some of the links above, but I need to free up some spare time to 'dive' into it a bit deeper.

FWIW, I have no interest in deeper diving for myself, but I have become somewhat curious as I've learned more about deco theory and why dive computers spit out the numbers they do. I do have a physics and math background from another life so that adds to my reasons to learn more.

 

[dmaziuk]

The basic method is recalculating in a loop, adding (e.g.) a minute of exposure on every iteration, until you hit your goal -- be it the NDL, or the time you can leave the stop and ascend to the next one. Buhlmann's formula in particular fits that very well. There are other options, e.g. there is a variant of Schreiner equation for calculating the NDL, but the length of deco stops I think you still have to do in a loop.

 

[BlueTrin]

Thanks @KWS for the response. I know you typed a lot, so I appreciate the effort. I do understand the concept that your saying. My question meant to be a little more specific of how the computer or software program manages the calculation...I don't mean the exact program code, but the mathematics and equations that one could program into a computer to ascertain the theoretical saturation of each compartment as a function of depth and time. I think I may have found the answer in some of the links above, but I need to free up some spare time to 'dive' into it a bit deeper.

FWIW, I have no interest in deeper diving for myself, but I have become somewhat curious as I've learned more about deco theory and why dive computers spit out the numbers they do. I do have a physics and math background from another life so that adds to my reasons to learn more.

So I have not read the whole thread, but I write quantitative models for a living.

Usually you can write it in more than one manner:
- for example you could brute force and put optimisation constraints then let the program find the solution
- sometimes when you know the equations of a problem you could just solve it and find a ‘closed form’ solution.

In both cases you’ll have to make a few assumptions as additional constraints/equations.

 

[dmaziuk]

So I have not read the whole thread, but I write quantitative models for a living.

Usually you can write it in more than one manner:
- for example you could brute force and put optimisation constraints then let the program find the solution
- sometimes when you know the equations of a problem you could just solve it and find a ‘closed form’ solution.

In both cases you’ll have to make a few assumptions as additional constraints/equations.

It is a "closed form" setup, the problem is that the equation gives you gas loading as a function of pressure and time, and you want to know the loading at some future point in time.

Tables are the form where you give it target pressure (depth) and it solves for time (NDL).