She unbound her hair and let it flow loose in the wind.
她解开头绳，让头发在风里自由地飘。
《柯林斯英汉双解大词典》
2
Blood vessels in the head tighten to stop the loss of body heat and then relax to let blood flow rise; that sudden rush of blood is what causes the headache.
头部的血管收紧以阻止身体热量的流失，然后放松让血液流动起来，血液的突然涌入是引起头痛的原因。
3
As the words begin to flow, the ideas will come from the shadows and let themselves be captured on your notepad or your screen.