straight-line flow

例句：

1. 1. The river has a straight-line flow through the town.
   这条河穿过城镇，水流呈直线。
2. 2. The car's engine produces a straight-line flow of exhaust gases.
   汽车的发动机产生一股直线的废气排放。
3. 3. The stream is a straight-line flow that runs through the forest.
   这条小溪是一条穿过森林的直线流水。