VPM Technical Discussion

[Robert C. Helling]

On 07 Mar 2014, at 23:27, Gopichand Paturi <gopichandpaturi at gmail.com> wrote:

Gopichand,

> I have been waiting for you on IRC to let you know my progress.
> Well, As I go through VPM, I'm developing keen interest to implement it, given the background of deco algorithm that you implemented.
> 
> I have gone through the permeability and other related concepts of surface tension very recently, as you discussed with me on irc.
> 
> Also, As far I see it, VPM is critically about the handling of bubbles in each compartment. I'm yet to know more detailed description of some constants like Regeneration time and 'S'(Skin constant). Let me know your idea,how to get these values for a specific bubble in a compartment.
> 
> I found out after detailed study on VPM is that handling the No Bubble Growth equation is critical step in the implementation of VPM. 
> Especially finding the radius of bubble is most important for finding supersaturated state.
> 

Great. Can you explain the “No Bubble Growth” equation to me? How is it derived?

> I have plans to put proper documentation and complete explanation of these algorithms into place in subsurface also as part of implementing it.
> (I will mention this in GSOC application)
> 
> Because doing so, I strongly believe would help extending it to new algorithms like RGBM etc, which helps subsurface in the future (I'm interested to work on the same after this summer).
> 

As far as I know, RGBM is not published. You have to buy a license to be told the details. If that is the case this is not compatible with open source.


> I also want to know how to maintain the track of continous compression details of bubble during descent. 
> As this is a continous function depending on Pa-PTC. I want to know how to implement these type of values.

I have to admit I don’t know what you are talking about.

Let me ask a very naive question: Are we going to track one bubble per compartment? And if yes, how is its initial size determined? Or do we have to simulate a whole range of initial sizes?

How does the backtracking part of the algorithm work? What exactly is the condition for success? How is that derived?

> 
> Do you actually trigger the above actions by your code running a continous loop checking for changes in the descent/ascent depth for a  constant time interval?

Except for “constant”, yes.

> Or Is it that we are not implementing a dive planner.So running this algorithm on predefined depths and changes would be far easier(i feel) .
> 

Both.

Sorry for not being very responsive at the moment. The more concrete your questions are the easier it is for me to answer them.

Best
Robert

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Robert C. Helling     Elite Master Course Theoretical and Mathematical Physics  
                      Scientific Coordinator                                   
                      Ludwig Maximilians Universitaet Muenchen, Dept. Physik    
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