[himanshu1khatri (OP)]

Hi there ....

am trying to release controlled amount of air (bubbles) through a grid of vents at the bottom plate of a tank filled with liquid .......was banking on surface tension to keep the thick liquid - silicon oil from
entering the 121 vents at the tank bottom (.25mm each)
turns out my naive ideas in physical chem. were wrong ......

details and drawings are downloadable at.... newbielink:http://www.4shared.com/file/3153539/5f33ff0d/sos.html [nonactive]

the liquid is entering the vents at the tank bottom ......seems i need one of the following...

some kindav separation membrane to allow only air passage (air passage has to be uniform all over the grid)
OR
another liquid thicker than silicon oil under silicon oil ....not entering the 121 (.25mm) vents
OR
Some special air liquid interfacing non return valve to let air thru but block returning liquid etc

anything anyone has to add....or detail in the above?.....


I would be extremely grateful for ANY kind of help or guidance ......these are urgent and desperate hours

do support......deadline only few days away...

cheers
HK
 

[daveshorts]

If you were using water I think that your strategy would work a lot better if the grill was hydrophobic, because if it is hydrophillic the water wets both sides of the grill and surface tension will not help you. I am not sure what materials would count as siliconeophobic, but it may be worth looking into. PTFE is generally phobic of most things so may work better.

If you just had a single small tube, you would probably not have a problem as the air is going to be flowing out of it all the time and the diameter is too small for a bubble to form. The problem with loads of holes above an empty chamber is that you can have an instability forming where more air comes out of the left hand side and the oil flows in on the right. To counteract what you really want is a constant volume per second out of all the holes rather than a constant pressure. probably going to take too long to build.

You probably don't actually need something of higher viscosity below the silicon oil, but something with more surface tension - like water, or possibly brine if your silicone oil is dense. I would then worry about the bubbles transferring from the water to the silicone oil.

I guess your other option would be to try and make the holes smaller where they are meeting the silicone, maybe you could get away by stretching some material over them. Not convinced it woudl work though.

[jysk]

The effect you're discribing reminds me of Neilep's "Clam Bottle Tub-Time Paradox" that is currently being discussed.

http://www.thenakedscientists.com/forum/topic.asp?TOPIC_ID=5140

Each of your 121 pin-holes might be creating it's own little vortex as you drive air through. These 121 inverted examples of meniscus might already be near their strength limits for providing uniform surface tension.

I didn't open the picture of your experiment. My comment is based on your description.

Mike

[jysk]

The effect you're discribing reminds me of Neilep's "Clam Bottle Tub-Time Paradox" that is currently being discussed.

http://www.thenakedscientists.com/forum/topic.asp?TOPIC_ID=5140

Each of your 121 pin-holes might be creating it's own little vortex as you drive air through. These 121 inverted examples of meniscus might already be near their strength limits for providing uniform surface tension.

I didn't open the picture of your experiment. My comment is based on your description.

Mike

[jysk]

The effect you're discribing reminds me of Neilep's "Clam Bottle Tub-Time Paradox" that is currently being discussed.

http://www.thenakedscientists.com/forum/topic.asp?TOPIC_ID=5140

Each of your 121 pin-holes might be creating it's own little vortex as you drive air through. These 121 inverted examples of meniscus might already be near their strength limits for providing uniform surface tension.

I didn't open the picture of your experiment. My comment is based on your description.

Mike