The flow inside a horizontal annulus due to the inner cylinder rotation is studied. The bottom of the annular space is partially blocked by a plate parallel to the axis of rotation, thereby destroying the circumferential symmetry of the annular space geometry. This flow configuration is encountered in the drilling process of horizontal petroleum wells, where a bed of cuttings is deposited at the bottom part of the annulus. The velocity field for this flow was obtained both numerically and experimentally. In the numerical work, the equations which govern the three-dimensional, laminar flow of both Newtonian and power-law liquids were solved via a finite-volume technique. In the experimental research, the instantaneous and time-averaged flow fields over two-dimensional meridional sections of the annular space were measured employing the particle image velocimetry (PIV) technique, also both for Newtonian and power-law liquids. Attention was focused on the determination of the onset of secondary flow in the form of distorted Taylor vortices. The results showed that the critical rotational Reynolds number is directly influenced by the degree of obstruction of the flow. The influence of the obstruction is more perceptible for Newtonian than for non-Newtonian liquids. The more severe is the obstruction, the larger is the critical Taylor number. The height of the obstruction also controls the width of the vortices. The calculated steady-state axial velocity profiles agreed well with the corresponding measurements. Transition values of the rotational Reynolds number are also well predicted by the computations. However, the measured and predicted values for the vortex size do not agree as well. Transverse flow maps revealed a complex interaction between the Taylor vortices and the zones of recirculating flow, for moderate to high degrees of flow obstruction.

Calcium carbonate scaling causes significant damage and financial losses to various industries, particularly in deep-water oil exploration. It is affected by factors like pressure, temperature, pH, solution chemistry, and surface finish. Surface finish is critical, as it interacts with the fluid and serves as a substrate for the anchoring of calcium carbonate crystals. However, many studies investigate this phenomenon under conditions that differ from those encountered in deep-water oil exploration. Tests are commonly performed under atmospheric pressure and lacking fluid flow or CO₂ influence, which limits their relevance to industrial conditions. This study aims to evaluate the influence of surface finish on the formation of calcium carbonate scaling under conditions that more closely resemble actual operating environments. 304 stainless steel was selected to replicate industrial conditions, owing to its chemical stability and common use in industrial settings. The tests were conducted in a plant with high-pressure capabilities, operating under continuous flow conditions with CO₂ injection. Controlled surfaces were prepared through metallographic polishing, machining, sandblasting, and laser texturing techniques. Surface characterization was performed using a 3D optical profilometer and scratch testing to measure the average adhesion force. The polymorphs formed were characterized by Raman spectroscopy. Fractal dimension analysis was applied to quantify the complexity of the analyzed surfaces. The results indicate that surfaces with higher fractal dimensions exhibit greater scaling mass and higher adhesion force. The main polymorph observed was calcite. Additionally, it was noted that the texture orientation relative to the flow affects scaling, with higher scaling values observed on surfaces oriented perpendicular to the flow. These findings are crucial for optimizing material selection and surface treatments in deep-water oil exploration, enhancing operational efficiency and reducing costs.