Concepts for transport phenomena-化工传递过程-名词解释-附答案.pdfVIP

Concepts for transport phenomena: 2 1. Whats a tensor(张量), methods to express a tensor, the meaning of the symbols ▽ and ▽. 张量：是矢量的推广，广义上说所有物理量均应以张量表达。（P5- 11-14 ） 三维n阶张量是需要3n个分量才能确定的量。每个分量都由n个单位矢量的排列组合确定 n 其相对方向。这3 个分量在坐标变换时必须按照确定的规律变换。 δ ∂ =∇ ∑ i hi i qi ∂ ∂ ∂ ∂ 在直角坐标系中： δ δ=∇ δ + + x y x ∂z y ∂ z ∂ =∇ ∇ • ∇2 2 1  ∂ h h ∂ ∂ h h ∂ ∂ h h ∂  2 3 1 3 1 2 ( ) ( =∇ ) (  ) + +  h h h qh q q h q q h q ∂ ∂ ∂ ∂ ∂ ∂ 1 2 3 1  1 1 22 2 33 3  2. The meaning of local derivatives, total derivatives and substantial derivatives as well as their differences. （P17 ） ∂P 设某物理量 ，将其对时间t 的偏微 称作局部倒数。 ( , , ) P f q q q t 1 2 3, ∂t