Flow and thermal characteristics of two interacting cylinders in the yield stress fluid

Abstract

In this work, steady and laminar flow of a viscoplastic fluid past two circular cylinders in a tandem arrangement has been investigated numerically. The governing differential equations for a Bingham model fluid have been solved over wide ranges of conditions as: Bingham number (0.01 ≤ Bn ≤ 100), Reynolds number (0.01 ≤ Re ≤ 40) and Prandtl number (10 ≤ Pr ≤ 100) in order to delineate the influence of each of these parameters on the momentum and heat transfer characteristics. In addition, the severity of the interactions between the two cylinders was modulated by varying the center-to-center distance between the two cylinders in the range 2 ≤ G ≤ 10. Detailed results in terms of the streamlines, isotherm contours, yielded/unyielded regions, shear rate profiles and the local Nusselt number in the vicinity of cylinders have been discussed here. Further insights are developed in terms of the distribution of velocity along the lines of symmetry. Finally, the overall behavior is captured in terms of the drag coefficient and average Nusselt number as functions of the pertinent governing parameters namely, Bn, Re, Pr and G. To facilitate the estimation of drag and Nusselt number in a new application, the present numerical results have been consolidated in terms of j factor as well as the Stanton number as functions of the pertinent dimensionless parameters. The present results reveal a significant impact of interference between the two cylinders, i.e., gap ratio on the detailed flow and thermal patterns and the overall characteristics