Saturday, July 21, 2007

Liquids bounce again
[I can’t resist putting up this little item, written for news@nature, because it is a classic kitchen experiment you can do yourself – the recipe is below.]

Jumping jets move from the bathroom to the kitchen

After bouncing shampoo, physicists now bring you bouncing cooking oil. A team in Texas has found that the trampolining of a liquid jet falling onto a bath of the same liquid is more common than expected.

Last year, a group in the Netherlands studied this bouncing effect for a jet of shampoo. The bounce, which was first reported over 40 years ago, happens because of the peculiar nature of shampoo, which gets thinner (less viscous) as it flows. A jet of it hitting a liquid surface is therefore lubricated by a thin layer at the interface, enabling it to bounce off rather than merge.

But the liquids now studied by Matthew Thrasher and colleagues at the University of Texas at Austin don’t have this property – they are viscous, but have ‘normal’ flow behaviour, like water.

The researchers directed a jet of oil vertically onto the surface of a tank of the same oil. They found that the jet could undergo both a ‘leaping’ rebound and a bizarre ‘flat’ bounce in which it sprang horizontally across the liquid surface.

The bounce here is due to a thin layer of air that separates the two liquid surfaces, the researchers say.

They point out that the effect can easily be recreated in a kitchen experiment with cooking oil. Just fill a glass pie dish with about 4 cm of oil and pour onto it a thin stream from a cup about 3-6 cm above the surface. While pouring, move the stream in a circle about once every 2 seconds (or rotate the dish on a Lazy Susan). The bounce can be encouraged by passing a small rod like a chopstick through the stream every now and then.


Anne Suzuki said...

i was searching for a jet seems that i landed on some kind of liquid jet which is i don't know what it is. :) but very interesting. =)

JimmyGiro said...

Viscosity thinning... lubrication by a thin layer... thin layer of air !?

Stand back folks, this is a job for ARMCHAIR PHYSICIST !!!

The Dutch suggestion seems to be the closest in what is probably the same type of mechanism, regardless of cooking oil or shampoo.

Both types of molecule are non-symmetrical, therefore have the potential to orient themselves. The shampoo probably is a liquid crystal to start with, whereas the cooking oil needs a push to orient itself.

The dropping column of liquid will stretch smoothly due to the lower end moving faster than the top, the surface molecules of the jet will therefore align momentarily due to sheer flow.

When the aligned jet meets the random bulk, there is a demarcation of form. In the same way that Mancunians taste the same after you put them in a food blender, despite the fact that city fans will not mix with united fans. Or thermals will appear to have 'clear defined' edges even though the difference between the gas interface is merely a small temperature and pressure gradient (or should that be small difference but large gradient?).

In order to blend, the demarcation needs to be removed. So the jet slows down front end first, and the tail end concertinas into it and undermines the orientation of the falling stretch.

Instead of using that laser for pretty fibre optic displays, they should have shone it at various reflection angles to the external surface of the jet, and measured the molecular alignment vis ellipsometry.

uhfdf said...

歐美a免費線上看,熊貓貼圖區,ec成人,聊天室080,aaa片免費看短片,dodo豆豆聊天室,一對一電話視訊聊天,自拍圖片集,走光露點,123456免費電影,本土自拍,美女裸體寫真,影片轉檔程式,成人視訊聊天,貼圖俱樂部,辣妹自拍影片,自拍電影免費下載,電話辣妹視訊,情色自拍貼圖,卡通做愛影片下載,日本辣妹自拍全裸,美女裸體模特兒,showlive影音聊天網,日本美女寫真,色情網,台灣自拍貼圖,情色貼圖貼片,百分百成人圖片 ,情色網站,a片網站,ukiss聊天室,卡通成人網,3級女星寫真,080 苗栗人聊天室,成人情色小說,免費成人片觀賞,

傑克論壇,維納斯成人用品,免費漫畫,內衣廣告美女,免費成人影城,a漫,國中女孩寫真自拍照片,ut男同志聊天室,女優,網友自拍,aa片免費看影片,玩美女人短片試看片,草莓論壇,kiss911貼圖片區,免費電影,免費成人,歐美 性感 美女 桌布,視訊交友高雄網,工藤靜香寫真集,金瓶梅免費影片,成人圖片 ,女明星裸體寫真,台灣處女貼圖貼片區,成人小遊戲,布蘭妮貼圖片區,美女視訊聊天,免費情色卡通短片,免費av18禁影片,小高聊天室,小老鼠論壇,免費a長片線上看,真愛love777聊天室,聊天ukiss,情色自拍貼圖,寵物女孩自拍網,免費a片下載,日本情色寫真,美女內衣秀,色情網,

liwo said...


女優王國,免費無碼a片,0800a片區,免費線上遊戲,無名正妹牆,成人圖片,寫真美女,av1688影音娛樂網,dodo豆豆聊天室,網拍模特兒,成人文學,免費試看a片,a片免費看,成人情色小說,美腿絲襪,影片下載,美女a片,人體寫真模特兒,熊貓成人貼,kiss情色,美女遊戲區,104 貼圖區,線上看,aaa片免費看影片,天堂情色,躺伯虎聊天室,洪爺情色網,kiss情色網,貼影區,雄貓貼圖,080苗栗人聊天室,都都成人站,尋夢園聊天室,a片線上觀看,無碼影片,情慾自拍,免費成人片,影音城論壇,情色成人,最新免費線上遊戲,a383影音城,美腿,色情寫真,xxx383成人視訊,視訊交友90739,av女優影片,

rubel mahomed said...

if the test out the plating zinc critical point pressure pipe, according to customer requirements can be properly galvanized steel reinforcement to greater affordability.
if not effectively detect the quality of galvanized steel so I suggest that the manufacturers do not ship to the buyer.
Take a look: ellipsometry