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Numerical investigation on the transition of fluid flow characteristics through a rotating curved duct

Hasan Mohammad Sanjeed, Islam MD. Sirajul, Badsha MD. Faisal, Mondal Rabindra Nath, Lorenzini Giulio

International Journal of Applied Mechanics and Engineering

2020

Vol. 25, no. 3

45--63

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 […] 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.

A bifurcation study of laminar thermal flow through a rotating curved duct with square cross-section

Mondal R. N., Roy S. C., Datta A. K., Uddin M. K.

International Journal of Applied Mechanics and Engineering

2012

Vol. 17, no. 4

1193-1211

In this paper, a comprehensive numerical study is presented for the fully developed two-dimensional flow of viscous incompressible fluid through a rotating curved duct with square cross section. Numerical calculations are carried out by using a spectral method and covering a wide range of the Taylor number […] for two cases of the Dean numbers, Case I: and Case II: . A temperature difference is applied across the vertical sidewalls for the Grashof number , where the outer wall is heated and the inner one cooled. The positive rotation of the duct about the center of curvature is imposed, and the effects of rotation (Coriolis force) on the flow characteristics are investigated. As a result, two and three branches of asymmetric steady solutions with two-, three- and four-vortex solutions are obtained by using the Newton-Raphson iteration method. Linear stability of the steady solutions is then investigated. When there is no stable steady solution, time evolution calculations as well as their phase spaces are obtained and it is found that the periodic solution turns into transitional chaos or chaotic solution through multi-periodic oscillation, if is increased. Secondary flow patterns and temperature profiles characterizing the flow are also obtained.