The present work studies the characteristics of the flow field inside an annular space formed by two concentric cylinders with rotation of the inner cylinder. The annular space was partially blocked by a plate parallel to the axis of rotation, thereby destroying the circumferential symmetry of the annular space geometry. This flow configuration encounters application on the modeling of drilling of horizontal petroleum wells where a bed of cuttings is formed at the bottom part of the annulus. This bed was modeled in the present work by a flat plate inserted into the annular space. The velocity field was investigated both numerically and experimentally. The equations governing the three-dimensional, laminar flow of a Newtonian fluid were solved via a finite-volume technique. The instantaneous and time-averaged flow fields over two-dimensional meridional sections of the annular space were measured employing the particle image velocimetry technique (PIV). Attention was focused on the determination of the onset of secondary flow in the form of distorted Taylor vortices. The results demonstrated that the critical rotational Reynolds number is directly influenced by the degree of obstruction of the flow given by the cylinder-to-plate gap. The smaller the gap, the larger the critical Taylor number. The gap dimensions control the width of the vortices. The calculated steady state axial flow profiles results agreed well with measurements. Transitions values of the rotational Reynolds numbers were also well predicted by the computations. Differences were found between measured and predicted values for the length of the Taylor vortices. Transverse flow maps revealed a complex interaction between Taylor vortices and zones of recirculating flow, for moderate to high degrees of flow obstruction.

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