Features of vortex flow fields in annuluses with different eccentricities

To further understand features of flow field during vortex in annulus, impacts of eccentricity variations on tangential velocity profile and resultant velocity profile of annulus under different rotation directions were determined according to the fluid dynamics theories and with continuity equation and N-S equation as controlling equations. In this study, systematic numerical simulations were performed on flows of Hershel-Bulkley fluid in annulus during vortex of drill pipes by using fluid dynamics. Through comparison of simulation data, it is seen that distributions of flow fields in the annulus are significantly different in different rotation directions. During rotation in positive direction, tangential velocity increases with the increases of revolution speed, speed of autorotation and eccentricity around wide clearance of annulus. During rotation in negative position, secondary flows are observed, and tangential velocity decreases reversely with the decreases of eccentricity in wide clearance of the annulus. Moreover, more obvious the trends of secondary flows, higher the frictional pressure losses. Proper application of these patterns may improve existing hydraulic theories for drilling operations to highlight properties of flow fields in the annulus and to provide theoretical guidance for design and optimization of hydraulic parameters for drilling operations.