Nowhere of water droplets?

[insight]

Since Air is the ideal gas, the ratio of water vapour and dry air is there. Where the ratio is higher, the humid air is going up, cooled and release heat energy (enthalpy), which means condensed and finally form water droplets to fall down to the earth surface again. What would happen to the water droplets where there is no gravity?

[Tormod]

I've seen a lot of cool pictures of astronauts drinking water that floats around the International Space Station like soap bubbles...really cool.

 

Here is a link to some experiments done on parabolic flights, with videos:

http://exploration.grc.nasa.gov/balloon/blob.htm

[Boerseun]

Seen a couple of interesting experiments on flames in zero-g as well. Seeing as the hot air from the flame can't go 'up', sucking in fresh oxygen at the bottom, if you strike a match in zero-g, it just makes a sphere of flame as the sulphur head ignites, and then dies as no oxygen is getting to the flame.

 

Apparently it's also impossible to boil water in space (apart from nuking it in a microwave). Seeing as convection doesn't happen, an element heats up and causes steam bubbles to isolate it from the rest of the water. So you end up with a container with boiling liquid in the one side, and cold liquid on the other side.

 

I'll look for the link for those pics - pretty cool flame ball, though.

[insight]

I've seen a lot of cool pictures of astronauts drinking water that floats around the International Space Station like soap bubbles...really cool.

 

Here is a link to some experiments done on parabolic flights, with videos:

http://exploration.grc.nasa.gov/balloon/blob.htm

 

That's interesting. Thanks for your link, Tormod. water droplets on the earth is a sphere apart from its speed. But, I saw it's like a turbulent structure in the space. Does this mean the shape of the droplets relate to Gravity and Its quantity? :)

[Boerseun]

Does this mean the shape of the droplets relate to Gravity and Its quantity? :)

Not completely. Water droplets are formed because of surface tension. The are spherical regardless of gravity (when falling - the spherical shape gets distorded by wind, etc.)

 

A specific liquid's droplets can only form up to a certain size on Earth before gravity overcomes the surface tension - think of a drop of water forming on a leaking tap. In space it'll grow to the size sphere you want, seeing as the only force in play then is surface tension.

[insight]

Not completely. Water droplets are formed because of surface tension. The are spherical regardless of gravity (when falling - the spherical shape gets distorded by wind, etc.)

 

A specific liquid's droplets can only form up to a certain size on Earth before gravity overcomes the surface tension - think of a drop of water forming on a leaking tap. In space it'll grow to the size sphere you want, seeing as the only force in play then is surface tension.

 

I know every energy state is always trying to be lowest like spherical shape. Actually when water droplets fall down, they aren't spherical. The gravity's pull transforms the spherical shapes into eye-drop shapes. If the wind and other disturbances are trying to stop them, eye-drop-shapes will be upside down. Furthermore, the droplets are gaining energy (i mean relative humidity is getting higher). :eek:

[steelengineer]

I think your question was whether there would be the same movement of water droplets, well, since there is no gravity, convection would not take place. however there would be motion of particles due to kinetic energy transfer through momentum. so in the end the entire volume of air would have the same humidity, the same water/dry air ratio. as to the size of the water droplet, however, that is a question to ask.

[cwes99_03]

You can heat water to boiling in zero g but only if the water is completely enclosed in a system and the system is heated, but yet there is a problem because once you heat the volume to boiling you can't open it without it exploding into space : )

 

As for why water droplets form teardrops in gravity wells, they form a tear drop for many many reasons, predominantly though it is drag that forms them into tear drops. The drag only affects the outer shell of the spherical drop. Thus pulling it in 'skins'. Of course gravity pulls the center down without any drag, thus the tear drop shape.

[insight]

I think your question was whether there would be the same movement of water droplets, well, since there is no gravity, convection would not take place. however there would be motion of particles due to kinetic energy transfer through momentum. so in the end the entire volume of air would have the same humidity, the same water/dry air ratio. as to the size of the water droplet, however, that is a question to ask.

Convection is nothing to do with gravity. As long as there is air to be transfered heat, convection takes place. Gravity pulls the air. If there is no gravity, there is no air and the convection also never happens. the density of air is lower in zero g, which interns to oversize the water doplet volume and the overall relative humidity ratio within the droplet boundary maintains.

:confused:

[cwes99_03]

Not to single you out, but everyone on this site, myself included needs to read their posts before posting to check on their gramar and spelling.

 

Convection can't occur in a vaccuum. That being said, we are talking about convection in zero g, not a vaccuum. Zero g occurs within the space ship, where the pressure of the air is maintained, not lower. If the air were to be less dense, or under pressurized, then the water-vapor level in the air would be able to be oversaturated when one introduces a large amount of water to it from a sealed vessel (some of it would instantly vaporize.) But this is off thread.

 

Explain what you mean by relative humidity level within the droplet boundary, because if you are within the boundary, we don't talk about humidity, we talk about disolved gases.

[insight]

Not to single you out, but everyone on this site, myself included needs to read their posts before posting to check on their gramar and spelling.

 

Convection can't occur in a vaccuum. That being said, we are talking about convection in zero g, not a vaccuum. Zero g occurs within the space ship, where the pressure of the air is maintained, not lower. If the air were to be less dense, or under pressurized, then the water-vapor level in the air would be able to be oversaturated when one introduces a large amount of water to it from a sealed vessel (some of it would instantly vaporize.) But this is off thread.

 

Explain what you mean by relative humidity level within the droplet boundary, because if you are within the boundary, we don't talk about humidity, we talk about disolved gases.

 

Firstly, i'm not in the droplet boundary. I'm outside it and see where it goes. :confused:

[Boerseun]

Convection is nothing to do with gravity. As long as there is air to be transfered heat, convection takes place. Gravity pulls the air. If there is no gravity, there is no air and the convection also never happens. the density of air is lower in zero g, which interns to oversize the water doplet volume and the overall relative humidity ratio within the droplet boundary maintains.

:confused:

No, convection has everything to do with gravity.

When something heats up, it expands. When it expands, it becomes more bouyant. Bouyancy causes the heated liquid/gas/whatever to rise, seeing as it is 'pressed away' by the less-bouyant cold stuff.

In a zero-g environment, there's no such thing as bouyancy - bouyancy being mediated, of course, by gravity.

Thus - in a zero-g environment, convection simply cannot happen. Diffusion will happen, but that's got to do with gas pressure, pressure not being dependent on gravity.

[Jay-qu]

I think it is funny how people have been throwing around the idea of 'tear drop' shaped when a tear drop is a drop of water(although its slightly saline):confused:... lol :confused:

[HydrogenBond]

If air was saturated with water vapor and was cooled further, the hydrogen bonding potential between the water molecules would be able to lower and the water would condense as tiny droplets. The smaller the droplet the higher the surface tension. The surface tension is also connected to hydrogen bonding on the perimeter; hydrogen than can not fully lower potential. The push would be to lower surface tension by the droplets combining to form less surface area per liquid volume. The water would also condense on surfaces that offer electrons to share as a way to lowering hydrogen bonding potential and surface tesion. The minimum potential shape would be a function of temperature and the surfaces present.

[UncleAl]

Hey git - fog, clouds.

[CraigD]

… Actually when water droplets fall down, they aren't spherical. The gravity's pull transforms the spherical shapes into eye-drop shapes …

This is a common misperception, owing to the fact that water droplets have this shape on flat surfaces such as window panes, where we usually see them. It’s practically impossible to see a falling raindrop with the naked eye.

 

While falling, they’re actually shaped like a thick hamburger patty or pancake (see http://ga.water.usgs.gov/edu/raindropshape.html). Even sites like these don’t, I think, have the shapes quite right – actual photos of raindrops I’ve seen look more like this.

[insight]

This is a common misperception, owing to the fact that water droplets have this shape on flat surfaces such as window panes, where we usually see them. It’s practically impossible to see a falling raindrop with the naked eye.

 

While falling, they’re actually shaped like a thick hamburger patty or pancake (see http://ga.water.usgs.gov/edu/raindropshape.html). Even sites like these don’t, I think, have the shapes quite right – actual photos of raindrops I’ve seen look more like this.

 

That's enlightening, thanks Craig. Totally different story! :hihi: