Flow resistance and head loss 水流阻力和能头损失
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。
The full round port area provides maximum flow capacity and minimum head loss.
完全的圆形流道截面能够提供最大的流量和最小的流压损失。
When submersible pumps for wells have qualified efficiency, the high head and flow of impellers will generate reactive power loss.
在效率合格的情况下，井用潜水泵的叶轮扬程和流量偏高时会产生无功损耗。
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