Abstract
A depth understanding of fluid flow past a curved duct having rectangular cross-section with different aspect ratios (l) are essential for various engineering applications such as in chemical, mechanical, bio-mechanical and bio-medical engineering. So highly ambitious researchers have given significant attention to study new characteristics of fluid flow in a curved duct. The flow characterization in the rectangular duct has been studied over a wide range of numerical and selective experimental studies. However, proper knowledge with the effects of Coriolis force for different aspect ratios is important for better understanding of the transitional behaviour and the subsequent heat generation, which is required to improve further. The purpose of this study is to reveal insight into the transitional flow pattern and heat transfer in a curved rectangular domain. The Navier-Stokes equations are solved using the spectral method, while the Crank-Nicolson method is used to solve the energy equation. An in-house FORTRAN code is developed to get the numerical solution. For post-processing purposes, Tecplot-360 and Ghost-script tools are used. The present study exposes development of Dean vortices that affect heat generation as well as thermal enhancement in the flow with underlying the flow controlling parameters, the Dean number (Dn), the Grashof number (Gr) and the Taylor number (Tr). Time-dependent results followed by phase spaces show that transient flow undergoes in the scenario ‘chaotic → multi-periodic→ periodic→ steady-state’ generating 2- to 8- vortices for the periodic/multi-periodic flow at 2000 ≤ Tr ≤ 2205 for l = 2, whereas similar sort of flow is observed in the range of 3100 ≤ Tr ≤ 3195 for l = 3. More complicated 4- to 13-vortex solutions are obtained for the chaotic flow regime at l = 2 in the range of 0 ≤ Tr < 2200 and at l = 3 in the range of 0 ≤ Tr < 3100. The chaotic flow that occurs at the certain range of Tr proficiently intensifies the heat transfer than the unperturbed, periodic or multi-periodic flow. The overall investigation reveals that in the rotating duct, the temperature-influenced buoyancy compulsion and centrifugal-coriolis joint forces are dominant, influencing the characteristic of the fluid and thus optimizing the transfer of heat. The present investigation will contribute to enhancing the understanding of fluid flow and heat transfer of internal heating/cooling/gas turbines, electric generators, biological systems, and some separation processes.
Highlights
Rotating flow and consequent heat conduction through the curved duct have been drawn considerable interest to the researchers for their vast applications in the field of fluids engineering and aviation engineering [1] and in biomedical engineering, for instance, inertial based cell separation [2,3]
To explore the effect of the rotational parameter (Tr) on the nonlinear behavior of the time-dependent solution, the time evaluation results have been investigated for Dean number (Dn) = 1500, and Grashof number (Gr) = 500 over a wide range of Tr
As seen in the secondary flow patterns, the secondary flow consists of two- or more-vortex solutions which are asymmetric with respect to the horizontal plane y = 0
Summary
Rotating flow and consequent heat conduction through the curved duct have been drawn considerable interest to the researchers for their vast applications in the field of fluids engineering (cooling and heating systems) and aviation engineering [1] and in biomedical engineering, for instance, inertial based cell separation [2,3]. The mismatch of the primary and secondary flows due to the centrifugal and Coriolis forces in the rotational bent duct influences the fluid flow and generates Dean vortices. These outcomes of rolling either increase or decrease in nonlinear mathematical features of flow that rely upon the instability of heat flux and the streaming region. In continuation of this study, very recently, Chanda et al [27,28] investigated the effects of heat-flux and curvature ratio on fluid flow and thermal distribution in a bent rectangular duct maintaining a temperature difference between the horizontal walls using the method that was used by Islam et al [29]. Bifurcation structure as well as flow transition and energy distribution through a bent rectangular duct considering a significant temperature difference between the vertical walls with combined effects of Coriolis and centrifugal forces is less performed, which attracts the authors to fill up this gap
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