(319e) Numerical Quantification of Rotational Flow in the Viscometer

The Fann 35 viscometer is widely regarded as the industry standard for drilling fluid viscosity measurement. Understanding the flow field in this viscometer is crucial for analyzing viscosity measurements and designing new viscometers for different engineering purposes and applications. In the Fann 35 viscometer, the flow in the annular space between the rotational sleeve and bob is recognized as Couette coaxial rotation flow, while the flow in the vertical and horizontal directions, which is small and therefore hard to visualize, is generally ignored. This paper discusses the development of a full three-dimensional (3D) computational fluid dynamics (CFD) model to simulate the flow field. The mixing effects through the small scale holes on the sleeve were captured. The results reveal that the velocity magnitudes in the vertical and horizontal directions are approximately two orders of magnitude smaller than the rotational velocity. The influences of density and viscosity of the Newtonian fluid were evaluated at various rotational speeds. Further, the flow field of the non-Newtonian fluid in the viscometer was also examined by assuming a Herschel-Bulkley viscosity model, which was used to estimate the rheology of a typical drilling fluid.