Return flow of the water down the beach is called backwash, which is commonly called undertow when the pull is strong.
水流顺着海滩回流到海洋中被称为回流，如果推力很大的话，通常被称为退浪。
美剧
And I don't see a way to return blood flow to the brain.
我不知道怎么让血液流回大脑。
英语百科
Return flow
Return flow is surface and subsurface water that leaves the field following application of irrigation water. While irrigation return flows is a point source, they are expressly exempted from permit requirements under the Clean Water Act (P.L. 92-500, as amended).