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<div dir="ltr" data-setdir="false">No River, nothing that complicated. Just curious if there is some formula or rule-of-thumb regarding how much displacement is required to get a sub started to the surface, from a specified depth. Assuming perfect neutral buoyancy any change to positive would theoretically start the process but in a practical sense some forces could counteract a minor change in positive buoyancy. Obviously it doesn't require 100% total displacement of the MBT, but will one pound do it? two? three? Just looking for a reasonable estimate, if one exists.</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false"><br></div><div><br></div>
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On Sunday, August 16, 2020, 12:12:31 PM EDT, River Dolfi via Personal_Submersibles <personal_submersibles@psubs.org> wrote:
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<div><div id="ydp425f6676yiv3895110884"><div dir="ltr">Jon, are you asking about how to correlate buoyancy condition with vertical speed through the water? IE "If I drain 50lb from the VBT and make myself 50lb positively buoyant, how long will it take me to reach the surface 600ft up?"<div><br></div><div>You would have to know the drag coefficient and a reference area of the sub in question in the up and down direction. Usually that kind of number is determined with fancy CFD or wind tunnel testing. I've got a couple data points about buoyancy vs vertical speed that I could crunch to get an approximate drag coefficient appropriate for small submersibles, then you could calculate the speed for any sub of a given cross sectional area.</div><div><br clear="all"><div><div dir="ltr" class="ydp425f6676yiv3895110884gmail_signature"><div dir="ltr"><div>Thanks,</div><div><br></div><div dir="ltr">-River J. Dolfi<div><div><br></div><div><a href="mailto:rdolfi7@gmail.com" rel="nofollow" target="_blank">rdolfi7@gmail.com</a></div></div></div></div></div></div></div></div></div>_______________________________________________<br>Personal_Submersibles mailing list<br><a href="mailto:Personal_Submersibles@psubs.org" rel="nofollow" target="_blank">Personal_Submersibles@psubs.org</a><br><a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" rel="nofollow" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br></div>
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