关键词: 粘性, 输流管道, 运动方程, 临界流速

Abstract: Considering the non-uniformity of the flow velocity distribution in a fluid-conveying pipe caused by the viscosity of real fluid, the centrifugal-force term in the equation of motion of the pipe is modified in the cases of laminar flow and two modes of turbulent flow. The modification factors are found to be 1.333, 1.020 and 1.037$\sim$1.055 for laminar flow in circular pipe, turbulent flow in smooth circular pipe and turbulent flow in rough circular pipe, respectively. The critical flow velocities for divergence in the above-mentioned three cases are found to be 13.4{\%}, 1.0{\%} and 1.8\%$\sim$2.6{\%}, respectively, lower than those for ideal fluid flow. The effects of fluid viscosity on the equation of motion and the critical flow velocity of fluid-conveying pipe are explicitly related to the flow mode only. The viscosity coefficient plays an implicit role via Reynolds number, which determines the flow mode.

Key words: viscosity, fluid-conveying pipe, equation of motion, critical flow velocity