Calculating SCUBA Depth with Exhaled Air and Terminal Velocity

  • Context: Undergrad 
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Discussion Overview

The discussion revolves around the feasibility of calculating SCUBA diving depth using the time it takes for exhaled air bubbles to reach the surface after being released. Participants explore the potential methods and equations that could be applied in this scenario.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that exhaling air and timing the ascent of bubbles could provide a method for estimating depth, questioning what the relevant equation might be.
  • Another participant expresses skepticism about the practicality of observing bubbles during a dive and emphasizes the importance of prior research in formulating questions.
  • Some participants propose that the size of the bubbles might serve as an indicator of depth, prompting inquiries about whether bubble size changes with depth.
  • There is a discussion about the relationship between the mass of the gas in the bubbles and their volume, with a participant noting that lung volume remains constant under pressure, raising concerns about measurement reliability.
  • A participant shares a resource regarding the terminal velocity of bubbles, suggesting it could be relevant to the discussion.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the feasibility or reliability of using exhaled bubbles to measure depth, with multiple competing views and uncertainties expressed throughout the discussion.

Contextual Notes

Limitations include the assumptions about bubble behavior at different depths, the reliability of visual observations underwater, and the need for a clear algorithm analogous to measuring height by timing a falling object.

Dr. Surgery
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So if you were scuba diving and your depth gauge broke, could you create a system where you exhale some air and record the time it took to reach the surface. If so, what would they equation look like?
 
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Dr. Surgery said:
So if you were scuba diving and your depth gauge broke, could you create a system where you exhale some air and record the time it took to reach the surface. If so, what would they equation look like?
Fun question. But first of all, when I'm scuba diving, it's hard for me to see my bubbles all the way to the surface. And second of all, we prefer for posters to show some effort in their questions -- what have you found in your reading about this question? :smile:
 
Maybe the size of the bubbles may be a rough indicator of the depth.
Have you observed a difference in the average size as you go deeper?
 
While you may be able to observe the difference of the mass of the gas of the bubbles, wouldn´t the volume be the same because it is about how your lungs(Constant volume) will hold at a given depth/pressure, and I am not sure how reliable it would be to measure it. I am looking for an algorithm similar to dropping a rock, and counting how many seconds it takes for it to land to calculate how high a cliff is.
 
I did a Google search on Bubbles Reach Terminal Velocity, and got lots of good hits. Here's a paper that may be helpful for you:

http://isites.harvard.edu/fs/docs/icb.topic1032465.files/Final%20Projects/Fluids%20Drag/Terminal%20Velocity.pdf

:smile:
 

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