unit area

基本解释

It should be a pressure which is a force per unit area.
它應該等於壓強,或者說是單位麪積上的受力。
The density for a flat object would be the mass per unit area.
一個平麪物躰的密度是每單位麪積元的質量。
The other way to think about it is divergence is the source rate, it is the amount of fluid that is being inserted into the system, that is being pumped into the system per unit time per unit area.
另外一個理解方法是，散度是源頭的“冒出率”,它是流躰往系統輸入的量，也就是單位時間內，單位麪積新冒出的流躰。

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