Numerical study of turbulent drag reduction over non-smooth surfaces of rotating-stationary disk system

Turbulent drag reduction has an important significance for energy conservation and emission reduction of the engineering fields, such as mechanical transmission and longdistance transport pipeline transportation. The air-oil two-phase flow model of non-smooth surfaces of rotating-stationary disk system was established based on the finite volume method, the volume of fluid method and RNG k-ε turbulence model. The flow field distribution of lubricant oil is obtained through the numerical analysis of three-dimensional Navier-Stokes equations of the two-phase of lubricating medium inside the rotating-stationary disk system. The turbulent boundary layer flow and stickiness resistance of the rotating-stationary disk system, as well as, the turbulent drag reduction capability by numerical calculation is investigated. The flow field of the smooth surfaces and non-smooth surfaces of rotating-stationary disk system are analyzed and the mechanism of turbulent drag reduction is discussed. The factors of influencing turbulent drag reduction are discussed by changing groove numbers, depth, and area ratio of grooves. The results indicate the grooves make it easier for air to enter the rotating disk system, and the film more easily broken, thus inhibiting the rise in the turbulent drag torque; the turbulent drag reduction efficiency will enhance with the number of grooves increase; will enhance with the depth of grooves increase and will enhance with the area ratio of grooves increase. The results can be used for the flow field analysis and optimization of the rotating-stationary disk system, especially supply a new method to the energy conservation and emission reduction.