当雷诺数为 2000 ~ 4000 时，流体的流动处在临界区，或是层流或是紊流，管道的阻力还不能作出确切的关联。When the Reynolds number is between 2000 and 4000, the fluid flow is in the critical region, either stagnant or turbulent.
题目内容(请给出正确答案)
当雷诺数为 2000 ~ 4000 时，流体的流动处在临界区，或是层流或是紊流，管道的阻力还不能作出确切的关联。When the Reynolds number is between 2000 and 4000, the fluid flow is in the critical region, either stagnant or turbulent.
