Pembentukan kepalan ais berbeza antara air tapis dgn air tangki

dauswq

    As the icicle turns   
        Drip by drip, machine freezes out existing theory


In icicle-growing experiments, scientists found that growing a smooth cone of ice requires pure water and a breeze, while other conditions create bent or lumpy pieces of ice like these.

A team of Canadian iciclologists has put to rest the notion that one frozen cone of drips is exactly the same as the next. By growing lots of icicles in controlled laboratory conditions, the scientists have uncovered evidence that runs counter to an earlier theory saying that all icicles should, by and large, assume the same uniform, platonic icicle shape. They posted their observations online August 11 at arXiv.org, with a supplementary series of videos on YouTube.

Physicists Stephen Morris and Antony Szu-Han Chen of the University of Toronto set out to test the existing theory’s prediction — that most icicles should assume a conical shape. Break off one of these perfect icicles anywhere along its length, and the fragment will be the exact same shape as the whole thing.

“As far as we know, no one has really systematically studied the shape of icicles and how they grow,” Morris says. “Nobody has really tried to fill in the physics of how the shape emerges.”

To grow icicles, the researchers built a frosty contraption made of a refrigerated box with a water drip at the top. The growing icicles rotated once every four minutes, like a rotisserie chicken, so that on average, the whole surface got the same treatment.

The lab-grown icicles grew to about half a meter long, and while some assumed the  iconic icicle shape, others came out looking much less than perfect. What’s more, the earlier theory posited that growing a perfectly shaped icicle required still air. But Morris and Chen found the opposite in their experiments: Most of the icicles grown in still air sprouted odd little legs at their tips, while those grown in the presence of moving air tended to be more ideally shaped.

Water quality also matters, Morris and Chen found. Icicles grown from distilled water were more likely to be perfectly conical than those grown from tap water, the team found. Tiny impurities in the tap water might be responsible for the lumpy and rippled shapes. “This is Toronto tap water, which is not especially wonderful,” Morris says.

Icicles are interesting in their own right (perhaps even more so to Canadians), but studying how they form is important for engineering problems such as ice on airplane wings or power lines. “If you can’t understand an icicle, you’re not going to understand how ice develops on a fast-blowing airplane wing,” Morris says.

dauswq

Reply 1# dauswq

ais dibentuk dr air tapis

ais dibentuk dr air tangki

perbezaan ni penting
cth dr aplikasi di atas - sms kapal terbang berlegar di ruang diudara yg sejuk

lagi satu,
dr eksperimen di atas kita dpt perhatikan
ais yg dibentuk oleh air tangki - besar kerana kehadiran particle

so negara yg sejuk misalnya
kepalan yg dibentuk lebih lonjong kerana kehadiran particle dlm udara

                                

Falling icicles kill record numbers in St Petersburg                                 
Falling icicles have killed five and injured 150 people in St Petersburg following Russia's coldest winter in three decades.

Russians walk underneath large icicles in central St. Petersburg
Photo: AFP / GETTY                                                        
                          



Apartment block roofs have caved in under the weight of snow with water seeping into people's homes and damaging books in the Russian National Library.
                        
But it is the unusually large number of people who have been struck by icicles that has caused the most concern.                                                      


        
In recent days, a six-month old baby received serious injuries after a chunk of ice dropped on her pram, an eight-year old boy suffered serious spinal damage after an icicle struck his back, and at least two people hit by falling ice are now in hospital fighting for their lives.
Valentina Matviyenko, the city's governor, has fired eleven officials accused of doing too little to keep the city's streets and rooftops free of snow and ice.
"Icicles should be removed with lasers or steam," she said. "If St. Petersburg experts throw up their hands and say that icicles should be removed using crowbars, then we will use crowbars."
Russians risk their lives each year as winter becomes spring causing melting icicles and blocks of ice to fall from roofs, often from a great height, onto defenceless pedestrians below.
Regional figures show icicles kill dozens of Russians each year. Local authorities responsible for regularly clearing roofs of snow and ice are usually blamed.


SUMBER: telegraph.co.uk

chewan

adakah pembentukan yg berbeza kepalan ais nie berpunca daripada kehadiran ionik spesis yg terdapat pada setiap jenis air yg di uji......

sekiranya betul..deionized water akan menghasilkan bentuk icicles yg lebih cantik berbanding distilled water

areenarena

tip jika untuk mengelak fros kat cermin di tempat sejuk-spray dengan air bercampur sedikit cuka...  tapi bile lah i nk pgi belanda, kene ngorat  datuk kot