Numerical Investigation on Flow Transition through a Curved ‎Square Duct with Negative Rotation

Application of the rotational phenomena in the curved ducts plays an important role in many engineering areas, so researchers are attracted to innovate something new in this area nowadays. In this regard, the current paper has performed the fluid flow through the curved duct for an extensive range of negative rotation (-۱۰ ≤ Tr ≤ -۱۵۰۰). The other useful parameters such as Dean number (Dn), Curvature (d), Grashof number (Gr), and Prandtl number (Pr) are considered fixed. The investigations are divided into four parts. In the first portion, linear stability of the flows through the duct is discussed. Then time evolution calculations of the unsteady solutions for different Taylor numbers are demonstrated in the “time vs. heat flux” plane. This inquiry shows that the flow undergoes various instabilities for increasing the Taylor number. Thirdly, two types of flow velocity, axial flow and secondary flow and the temperature profiles are represented. It is obtained that two up to six vortex secondary flows are found for the regular and irregular oscillation and the flow patterns are different for a fixed period for regular oscillation. To show more clarity of the periodic and chaotic flow, power spectrum density is further examined. However, it is observed that the flows are mixed and enhanced heat transfer because of the acting of centrifugal force, Coriolis force, and heating induced buoyancy force on the duct. Finally, the numerical results are compared with the experimental data which shows that the numerical data fully matches with the experimental outcome.

Keywords:

Linear stability , secondary flow , time-dependent solutions , power spectrum density , Experimental results‎