blank diameter

例句：

1. 1.The blank diameter of the pipe is20 cm.
   管子的空白直径是20厘米。
2. 2. The engineer measured the blankdiameter of the pipe accurately.
   工程师准确地测量了管子的空白直径。
3. 3. Theblank diameter of the pipewas used to calculate its volume.
   管子的空白直径被用来计算其体积。