It is found that the star_shaped nozzle jet has a shorter initial section and slower velocity attenuation along the jet centerline in the main region than the round nozzle jet.
实验发现，星形喷嘴射流与普通圆射流相比，其射流初始段较短，但基本段内速度随喷距衰减的速率较低。
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The initial section of tunnel had to be dug by hand.
隧道的起始部份不得不人工挖掘。
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