当量长度
参考答案：
流体通过某一局部障碍处的局部压头损失，折合成相当于与其有相同管径的一定长度的直管沿程压头损失，这个直管长度称为局部障碍的当量长度。
一2正方形六周长和它六边长六比是______，比值是______．
The would-be taxi drivers have to a very tough training period to get their licenses. [ ]
A. go through
B. get through
C. pass through
D. put through
