粗糙表面能减少水的阻力-凯发k8官网

粗糙表面能减少水的阻力
文章来源:未知 文章作者:enread 发布时间:2014-01-18 05:25 字体: [ ] 
(单词翻译:双击或拖选)
from the 1(圆滑的) 2 of 3 yachts to michael phelps' shaved legs, most objects that move through the water quickly are also smooth. but researchers from ucla have found that 4(崎岖不平) can sometimes be better. "a properly designed rough surface, contrary to our intuition(直觉), can reduce skin-5 drag," said john kim, a professor in the mechanical and 6 engineering department at ucla. kim and his colleagues modeled the fluid flow between two surfaces covered with tiny 7. they found that even in turbulent conditions the rough surface reduced the drag created by the friction of flowing water. the researchers report their findings in the journal physics of fluids.
 
the idea of using a rough surface for reduced drag had been explored before, but resulted in limited success. more recently scientists have begun experimenting with rough surfaces that are also extremely difficult to wet, a property called superhydrophobicity(超疏水). in theory this means that the surfaces can trap air bubbles, creating a hydrodynamic cushion, but in practice they often lose their air cushions in 8 flows.
 
the ulca team chose to model a superhydrophobic surface design that another group of researchers at ucla had already observed could keep air pockets 9, even in turbulent conditions. the surface was covered with small ridges 10 in the direction of flow.
 
the researchers modeled both laminar and turbulent flows, and unexpectedly found that the drag-reduction was larger in turbulent conditions. the irregular 11 and 12 vortices in turbulent flows on smooth surfaces generally increase drag, kim explained. however, the air cushion created by the superhydrophobic ridges altered the turbulent patterns near the surface, reducing their effect, he said.
 
the team expects insights 13 from their numerical simulations to help further refine the design of rough, drag-reducing surfaces. further down the line, such surfaces might cover the undersides of 14 15 and passenger ships. "it could lead to significant energy 16 and reduction of greenhouse gas emissions," kim said.


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1 zeszj     
adj.光滑的,井然有序的;v.使光滑,梳拢
参考例句:
  • women preferred sleek,shiny hair with little decoration.女士们更喜欢略加修饰的光滑闪亮型秀发。
  • the horse's coat was sleek and glossy.这匹马全身润泽有光。
2 f3061f8d41af9c611111214a4e5b6d16     
船体( hull的名词复数 ); 船身; 外壳; 豆荚
参考例句:
  • hulls may be removed by aspiration on screens. 脱下的种皮,可由筛子上的气吸装置吸除。
  • when their object is attained they fall off like empty hulls from the kernel. 当他们的目的达到以后,他们便凋谢零落,就象脱却果实的空壳一样。
3 1ksz3w     
n.竞赛,赛马;adj.竞赛用的,赛马用的
参考例句:
  • i was watching the racing on television last night.昨晚我在电视上看赛马。
  • the two racing drivers fenced for a chance to gain the lead.两个赛车手伺机竞相领先。
4 388efa5a1928af47bc06cf04d4d4af86     
n.崎岖不平
参考例句:
  • given the bumpiness of the road ahead, you might be better off with a crash helmet. 考虑到你面前这条颠簸的道路,你最好还是配个头盔吧。 来自互联网
5 jqmzr     
n.摩擦,摩擦力
参考例句:
  • when joan returned to work,the friction between them increased.琼回来工作后,他们之间的摩擦加剧了。
  • friction acts on moving bodies and brings them to a stop.摩擦力作用于运动着的物体,并使其停止。
6 ck2yf     
adj.航空的,宇宙航行的
参考例句:
  • the world's entire aerospace industry is feeling the chill winds of recession.全世界的航空航天工业都感受到了经济衰退的寒意。
  • edward murphy was an aerospace engineer for the us army.爱德华·墨菲是一名美军的航宇工程师。
7 9198b24606843d31204907681f48436b     
n.脊( ridge的名词复数 );山脊;脊状突起;大气层的)高压脊
参考例句:
  • the path winds along mountain ridges. 峰回路转。
  • perhaps that was the deepest truth in ridges's nature. 在里奇斯的思想上,这大概可以算是天经地义第一条了。
8 rutyd     
adj.混沌的,一片混乱的,一团糟的
参考例句:
  • things have been getting chaotic in the office recently.最近办公室的情况越来越乱了。
  • the traffic in the city was chaotic.这城市的交通糟透了。
9 eb21b3b8e7dad36e21d322e11b46715d     
v.使陷入圈套,使入陷阱( entrap的过去式和过去分词 )
参考例句:
  • he was entrapped into undertaking the work. 他受骗而担任那工作。 来自《简明英汉词典》
  • he felt he had been entrapped into marrying her. 他觉得和她结婚是上了当。 来自辞典例句
10 165f93b99f87c219277d70d866425da6     
adj.对齐的,均衡的
参考例句:
  • make sure the shelf is aligned with the top of the cupboard.务必使搁架与橱柜顶端对齐。
11 5ffd9bfff797526ec241b97cfb872d61     
波动,涨落,起伏( fluctuation的名词复数 )
参考例句:
  • he showed the price fluctuations in a statistical table. 他用统计表显示价格的波动。
  • there were so many unpredictable fluctuations on the stock exchange. 股票市场瞬息万变。
12 ngazzr     
v.旋转,打旋( swirl的现在分词 )
参考例句:
  • snowflakes were swirling in the air. 天空飘洒着雪花。 来自《现代汉英综合大词典》
  • she smiled, swirling the wine in her glass. 她微笑着,旋动着杯子里的葡萄酒。 来自辞典例句
13 83f6cdf195a7d487666a71e02179d977     
v.一点点地收集(资料、事实)( glean的过去式和过去分词 );(收割后)拾穗
参考例句:
  • these figures have been gleaned from a number of studies. 这些数据是通过多次研究收集得来的。
  • a valuable lesson may be gleaned from it by those who have eyes to see. 明眼人可从中记取宝贵的教训。 来自《现代汉英综合大词典》
14 6tcyg     
n.(一只船或一架飞机运载的)货物
参考例句:
  • the ship has a cargo of about 200 ton.这条船大约有200吨的货物。
  • a lot of people discharged the cargo from a ship.许多人从船上卸下货物。
15 fc9307c2593b522954eadb3ee6c57480     
n.血管( vessel的名词复数 );船;容器;(具有特殊品质或接受特殊品质的)人
参考例句:
  • the river is navigable by vessels of up to 90 tons. 90 吨以下的船只可以从这条河通过。 来自《简明英汉词典》
  • all modern vessels of any size are fitted with radar installations. 所有现代化船只都有雷达装置。 来自《现代汉英综合大词典》
16 zjbzgu     
n.存款,储蓄
参考例句:
  • i can't afford the vacation,for it would eat up my savings.我度不起假,那样会把我的积蓄用光的。
  • by this time he had used up all his savings.到这时,他的存款已全部用完。
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