fluid 的物理問題...... 高手請進

家仁

2011-08-30 7:38 pm

我想知....(1)係咪所有liquid 都係impressible...而gas就5係?
(2)係bernulli's principle入面...點解個其中一個pressure既方向係順住d fluid 流既方向..而另一個逆方向acting on the fluid??
(3)一個有eddies既fluid...點解d particles internal energy 會上升同form sound energy 而令到個ke loss左?

更新1:

SOR (1)係imcompressible..串錯左... (2)戈個:http://www.4physics.com/phy_demo/fluid-flow-to-right.gif 問緊p1同p2點解咁既方向

更新2:

(1)咁點解bunsen burner入面又可以用continuity 條式??..佢入面係gas... (2)咁佢地既pressure volume 一5一樣???

更新3:

更正(2)咁佢地既pressure value 一5一樣???

回答 (1)

天同

2011-08-30 10:09 pm

✔ 最佳答案

1. In practice, you could regard liquids as imcompressible because most liquids have a large bulk modulus (e.g. water: 2.15 x 10^9 Pa), whereas gases have much lower bulk modulus (e.g. air: 1.42 x 10^5 Pa). Liquids are thus much much harder to compress.

2. In fact, pressure at a point exerts in all direction. This is one of the inherent properties of fluid pressure.

The "arrows" only indicates the directions of pressure that are of relevance to the explanation of Bernoulli's Prinicple.

3. Your question is not clear. Is there any specific example?

2011-08-31 20:02:10 補充：
Q:咁點解bunsen burner入面又可以用continuity 條式??..佢入面係gas
A: why not ? Continuity equation is just another interpretation of "conservation of mass". The flow of gas in a bunsen burner observes mass conservation.

2011-08-31 20:03:49 補充：
Q:咁佢地既pressure value 一5一樣???
A: any fluid (liquid or gas) flows from high to low pressure. The same principle applies to the flow of gas in a bunsen burner.

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