Numerical Investigation on the Transition of Fluid Flow Characteristics Through a Rotating Curved Duct

Abstract

Time-dependent flow investigation through rotating curved ducts is utilized immensely in rotating machinery and metal industry. In the ongoing exploration, time-dependent solutions with flow transition through a rotating curved square duct of curvature ratio 0.009 have been performed. Numerical calculations are carried out for constant pressure gradient force, the Dean number Dn = 1000 and the Grashof number Gr=100 over a wide range of the Taylor number values –1500 ≤ Tr ≤ 1500 for both positive and negative rotation of the duct. The software Code::Blocks has been employed as the second programming tool to obtain numerical solutions. First, time evolution calculations of the unsteady solutions have been performed for positive rotation. To clearly understand the characteristics of regular and irregular oscillations, phase spaces of the time evolution results have been enumerated. Then the calculations have been further attempted for negative rotation and it is found that the unsteady flow shows different flow instabilities if Tr is increased or decreased in the positive or in the negative direction. Two types of flow velocities such as axial flow and secondary flow and temperature profiles have been exposed, and it is found that there appear two- to four-vortex asymmetric solutions for the oscillating flows for both positive and negative rotation whereas only two-vortex for the steady-state solution for positive rotation but four-vortex for negative rotation. From the axial flow pattern, it is observed that two high-velocity regions have been created for the oscillating flows. As a consequence of the change of flow velocity with respect to time, the fluid flow is mixed up in a great deal which enhances heat transfer in the fluid.

Effects of Rotation on Unsteady Fluid Flow and Forced Convection in the Rotating Curved Square Duct With a Small Curvature

“…Though their study discussed heat transfer in a three-dimensional coordinate system, the investigation is limited for low Reynolds number. Hasan et al [55][56][57] adopted spectral technique to explore time-dependent flow characteristics across the circular and non-circular channels including centrifugal and body force effects. However, no study is published so far that describes hydrothermal behavior of transient flow characteristics and energy distribution with forced convection in a curved square geometry with the effects of rotation, namely, the study which is successfully accomplished in this paper.…”

A computational modeling on transient heat and fluid flow through a curved duct of large aspect ratio with centrifugal instability

“…Umavathi and Bég [9] tried to show the three-dimensional contours of secondary flow and explained the characteristics of two different fluids both theoretically and experimentally. Hasan et al [37] and Sultana et al [38] established a relation between the axial and secondary velocity and the isotherms for the curved duct flow. They alongside obtained that flow velocities are stronger in periodic, multi-periodic and chaotic flows than the steady-state flow.…”

A Computational Study on Fluid Flow and Heat Transfer Through a Rotating Curved Duct with Rectangular Cross Section

“…Nevertheless, unsteady characteristics of flow in a convex duct having higher aspect-ratio were explored by Yanase et al [15]. Different types of hydrodynamic instability including steady-state, periodic, multi-periodic, and chaotic flow have been analyzed by Wang et al and Hasan et al [16,17]. Recently, Hasan et al [18] conducted a computational and laboratory-based experiment on fully developed periodic oscillating flow in a square channel.…”