solid 固体liquid 液体gas 气体 - ckw.ppt

GOT IT? 15.2. A large tank is filled with liquid to level h1 . 一個大水槽裝了 h1 高的液體。 It drains through a small pipe whose diameter varies. 它的泄口是一條口徑有變化的細管。 Emerging from each section of pipe are vertical tubes open to the atmosphere. 細管的每一段都有一條外通大氣的直立的管。 Although the picture shows the same liquid level in each pipe, 雖然圖中這些管的液面都一樣高， they really won’t be the same. 其實它們都不一樣。 Rank order the levels h1 through h4. 把 h1 到 h4 從大到小排序。 ordered inversely by flow speed 依流速反排序 Flight Lift 飛行升力 Aerodynamic lift 空氣動態升力 Top view on a curved ball : spin 從上往下看一個彎球: 有自旋 Blade pushes down on air旋槳把空氣往下推 Air pushes up (3rd law) 空氣往上推 (第三定律) Faster flow, lower P : uplift. 流速較快，P 較低：升力 Top view on a straight ball : no spin 從上往下看一個直球: 無自旋 氣流 Application: Wind Energy 風能 A chunk of air, of speed v density ?, 一團空氣，其速度為 v ，密度為 ?, passing thru a turbine of area A in time ?t, has kinetic energy 在 ?t 時間內通過一部面積為 A 的渦輪機。其動能為 available power per unit area = 可用的單位面積功率 Better analysis ? 好一點的分析 For 設 Present tech gives 80% of this. 現在的科技可達此值的80% 。 15.6. Viscosity Turbulence 粘性 亂流 Smooth flow becomes turbulent. 平順的氣流變成亂流 Viscosity: friction due to momentum transfer between adjacent fluid layers or between fluid wall. 粘性: 因相隣流層或流體與容璧之間的動量交換而產生的阻力。 B.C.: v = 0 at wall 邊際條件 drag on moving object. 拖住移動物件 provide 3rd law force on propellers. 為螺旋槳提供第三定律力 stabilize flow. 穩定流量 flow with no viscosity 無粘性流 flow with viscosity 粘性流 * 15. Fluid Motion 流體運動 Density Pressure 密度 壓力 Hydrostatic Equilibrium 流體靜力平衡狀態 Archimedes’ Principle Buoyancy 阿基米德原理 浮力 Fluid Dynamics 流體力學 Applications of Fluid Dynamics 流體力學的應用 Viscosity Turbulence 粘性 亂流 Why is only the “tip of the iceberg ” above water? 為甚麼只看到〝冰山一角〞? ?ice is only slightly less than ?water. ?ice 只比 ?water 小一點點。 Fluid = matter that flows under external forces = liquid or gas. solid 固體 liquid 液體 gas 氣體 inter-mol forces 分子間的作