F(bot), and only F(bot), is the upward buoyancy force.Thistle Dome lacks that lower surface contact, so there's no liquid displacement,
Quote from: LMT on 11/23/2016 05:33 pmF(bot), and only F(bot), is the upward buoyancy force.Thistle Dome lacks that lower surface contact, so there's no liquid displacement, A dome (inverted bowl) cupped on the bottom of a sink/bath/pool/etc also lacks the "lower surface contact", yet experiences buoyancy.Your dome is no different than building a dome on the bottom of any lake/ocean on Earth. You cannot just arbitrarily exclude buoyancy.
Quote from: Paul451 on 11/24/2016 01:54 amQuote from: wstewart on 11/23/2016 05:33 pmF(bot), and only F(bot), is the upward buoyancy force.Thistle Dome lacks that lower surface contact, so there's no liquid displacement, A dome (inverted bowl) cupped on the bottom of a sink/bath/pool/etc also lacks the "lower surface contact", yet experiences buoyancy.Your dome is no different than building a dome on the bottom of any lake/ocean on Earth. You cannot just arbitrarily exclude buoyancy.No, you just confused force from air pressure with buoyancy force.
Quote from: wstewart on 11/23/2016 05:33 pmF(bot), and only F(bot), is the upward buoyancy force.Thistle Dome lacks that lower surface contact, so there's no liquid displacement, A dome (inverted bowl) cupped on the bottom of a sink/bath/pool/etc also lacks the "lower surface contact", yet experiences buoyancy.Your dome is no different than building a dome on the bottom of any lake/ocean on Earth. You cannot just arbitrarily exclude buoyancy.
Quote from: LMT on 11/24/2016 03:31 amQuote from: Paul451 on 11/24/2016 01:54 amQuote from: LMT on 11/23/2016 05:33 pmF(bot), and only F(bot), is the upward buoyancy force.Thistle Dome lacks that lower surface contact, so there's no liquid displacement, A dome (inverted bowl) cupped on the bottom of a sink/bath/pool/etc also lacks the "lower surface contact", yet experiences buoyancy.Your dome is no different than building a dome on the bottom of any lake/ocean on Earth. You cannot just arbitrarily exclude buoyancy.No, you just confused force from air pressure with buoyancy force. Buoyancy is in addition to the uplift from air-pressure.
Quote from: Paul451 on 11/24/2016 01:54 amQuote from: LMT on 11/23/2016 05:33 pmF(bot), and only F(bot), is the upward buoyancy force.Thistle Dome lacks that lower surface contact, so there's no liquid displacement, A dome (inverted bowl) cupped on the bottom of a sink/bath/pool/etc also lacks the "lower surface contact", yet experiences buoyancy.Your dome is no different than building a dome on the bottom of any lake/ocean on Earth. You cannot just arbitrarily exclude buoyancy.No, you just confused force from air pressure with buoyancy force.
Quote from: Paul451 on 11/24/2016 07:48 amQuote from: wstewart on 11/24/2016 03:31 amQuote from: Paul451 on 11/24/2016 01:54 amQuote from: wstewart on 11/23/2016 05:33 pmF(bot), and only F(bot), is the upward buoyancy force.Thistle Dome lacks that lower surface contact, so there's no liquid displacement, A dome (inverted bowl) cupped on the bottom of a sink/bath/pool/etc also lacks the "lower surface contact", yet experiences buoyancy.Your dome is no different than building a dome on the bottom of any lake/ocean on Earth. You cannot just arbitrarily exclude buoyancy.No, you just confused force from air pressure with buoyancy force. Buoyancy is in addition to the uplift from air-pressure.It doesn't work that way.
Quote from: wstewart on 11/24/2016 03:31 amQuote from: Paul451 on 11/24/2016 01:54 amQuote from: wstewart on 11/23/2016 05:33 pmF(bot), and only F(bot), is the upward buoyancy force.Thistle Dome lacks that lower surface contact, so there's no liquid displacement, A dome (inverted bowl) cupped on the bottom of a sink/bath/pool/etc also lacks the "lower surface contact", yet experiences buoyancy.Your dome is no different than building a dome on the bottom of any lake/ocean on Earth. You cannot just arbitrarily exclude buoyancy.No, you just confused force from air pressure with buoyancy force. Buoyancy is in addition to the uplift from air-pressure.
How about this?
I argue that all the plastic-wrap that is clearly curved downwards is feeling a downwards force.
No part of it attempts to form an upwards bubble.
Interestingly, the flat plastic-wrap covering the bowl itself remained pretty much flat as far as I could tell. It felt strange to the touch, not under tension that I could tell.
Note: when I pulled a corner of the black tape up allowing water to enter, the plastic wrap immediately converted to an upward pulling dome shape, even as the water began pouring down the plughole.
Quote from: KelvinZero on 11/25/2016 07:56 amNo part of it attempts to form an upwards bubble....I suspect in your set-up, some air was able to leak through out the drain.Try repeating it with a plug in place, or on a solid part of the sink.
though the bowl itself strains upward. So something has to be strong, but not your transparent domed roof.
Quote from: KelvinZero on 11/25/2016 10:14 pmthough the bowl itself strains upward. So something has to be strong, but not your transparent domed roof.Remember in that case it's the bowl that contains the air, and the bowl that experiences the buoyancy. The cling-film is flat, thus experiences no buoyancy.[*] To replicate wstewart's submerged dome, you'd need to hold an air bubble with the cling-film alone. For example, a flat plate with an air-filled cling-film "dome", or taping an air-filled "dome" of cling-film to the bottom of the sink before filling it. The buoyancy is present no matter what you do.
Im not fussed about that part though. The dome has to be connected to a massive monolithic piece of stone. The stone has to perform the roll of this bowl. If the density of the dome+stone is less than that of water, it would rise.
Quote from: Paul451 on 11/26/2016 03:57 amQuote from: KelvinZero on 11/25/2016 10:14 pmthough the bowl itself strains upward. So something has to be strong, but not your transparent domed roof.Remember in that case it's the bowl that contains the air, and the bowl that experiences the buoyancy. The cling-film is flat, thus experiences no buoyancy. To replicate wstewart's submerged dome, you'd need to hold an air bubble with the cling-film alone. For example, a flat plate with an air-filled cling-film "dome", or taping an air-filled "dome" of cling-film to the bottom of the sink before filling it. The only interesting point to me is that the material of the dome itself does not feel huge forces, or any particular force at all if the air pressure inside balances the water pressure outside.
Quote from: KelvinZero on 11/25/2016 10:14 pmthough the bowl itself strains upward. So something has to be strong, but not your transparent domed roof.Remember in that case it's the bowl that contains the air, and the bowl that experiences the buoyancy. The cling-film is flat, thus experiences no buoyancy. To replicate wstewart's submerged dome, you'd need to hold an air bubble with the cling-film alone. For example, a flat plate with an air-filled cling-film "dome", or taping an air-filled "dome" of cling-film to the bottom of the sink before filling it.
and it is this imbalance that tries to lift the floor up if any ambient water pressure can get beneath it.
That's not the case. You are confusing the flat cover (which doesn't experience buoyancy) with the walls of a dome.The dome will be crushed in from the side, and push up through the top. (Essentially it's trying to form a sphere at the same time as it's trying to rise.)
The roof could be a flat surface and not a dome...
...the roof, which does not need any particular strength if the air is at the same pressure as the water. At 30 meters on Mars that would match earth sealevel.
I imagine pillars dotted around because even if the roof is at equilibrium, it is not particularly stable and could even exhibit waves.
The transparent roof could be quite cheap. The underside can be as cheap, rigid and as heavy as you like, ideally a massive piece of ground but it could also be a freefloating thing build of concrete or whatever.
For something underwater I don't care about the sides.
Sandwich Composite PanelsThese panels, made of plywood on both sides with core insulation between them, were used in the construction of modular structures (living accommodation, kitchen, etc.).... [T]imber frame was used and the panel thickness was 124 mm (12 mm thick marine plywood on each side and 100 mm core polyurethane foam insulation)... [T]he floor needed additional insulation, because temperatures varied from -4ēC at the floor to 15ēC at the ceiling.
Re: Insulation in a tunnel.You guys do realise that an inhabited space will need to get rid of heat, not retain it?