Abstract
Due to widespread applications of the bent ducts in engineering fields such as in chemical, mechanical, bio-mechanical and bio-medical engineering, scientists have paid considerable attention to invent new characteristics of fluid flow in a bent duct (BD). In the ongoing study, a spectral-based numerical technique is applied to explore flow characteristics and energy distribution through a loosely bent square duct (BSD) of small curvature. Flow is accelerated due to combined action of the non-dimensional parameters; the Grashof number Gr (=1000), the curvature (=0.001), and the Prandtl number Pr (=7.0) over a wide domain of the Dean number . Fortran code is developed for the numerical computations and Tecplot software with Gost Script and Gost View is used for the post-processing purpose. The numerical study investigates steady solutions (SS) and as a result, a structure of six-branches of SSs composed of 2- to 6-vortex solutions is obtained. Then oscillating behavior with flow transition is discussed by obtaining time-dependent solutions followed by power-spectrum analysis. Results show that the trend of unsteady flow (UF) undergoes in the sequence ‘steady-statemulti-periodicsteady-statechaoticmulti-periodicchaotic’, if Dn is increased. Asymmetric 2- to 4-vortex solutions are obtained for UF. Convective heat transfer (CHT) is then examined obtaining temperature gradients and energy contours, and it is found that CHT is significantly enhanced by the secondary flow (SF). The present study reveals that the role of secondary vortices over heat transfer (HT) is highly significant and HT occurs substantially for the chaotic solutions. Finally, for the interest of validation, the present numerical result is compared with the previously published experimental outcomes, and a good agreement is remarked.
Highlights
Because of tremendous applications of the bent ducts (BD) in physical and natural sciences, bio-mechanical and bio-medical engineering, many highly ambitious researchers have given substantial attention in studying the flow and heat transfer (HT) through a BD
Fluid is accelerated under combined action of the 3 non-dimensional parameters; the Dean number (Dn), which is the pressure gradient parameter that accelerates fluid flow along the centre-line of the duct; the Grashof number (Gr), which is the buoyancy force parameter caused due to temperature difference between the walls and the curvature δ creates centrifugal force
A spectral-based numerical approach on fluid flow through a bent square duct (BSD) with bottom and outer-wall heated while the upper and inner walls in room temperature have been investigated for small curvature varying the Dean number for 0 < Dn ≤ 5000
Summary
Because of tremendous applications of the bent ducts (BD) in physical and natural sciences, bio-mechanical and bio-medical engineering, many highly ambitious researchers have given substantial attention in studying the flow and HT through a BD. The flow pattern inside the aorta and the bifurcation airways of the lung are intricate due to the complex curvature of the. The blood flow or the fluid flow inside the aorta or the bent channel respectively creates SFs causing the centrifugal force, and this SF along with the direction of the axial flow act at the right angle to the main flow direction. The curvature of the aorta and the lung airways shows different physically interesting flow characteristics for the pressuredriven flow. A lot of practical applications like fluid transportation, turbo machinery, gas turbines, heat exchangers, refrigeration, air conditioning system, ventilators, combustion engines, chemical reactors, centrifugal pumps etc., may be mentioned, which attracts the researchers to do advanced research in this fascinating field
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