Unsteady characteristics of laminar free convection in an enclosure in the presence of power law fluid at Ra = 10 7
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DOI 10.1007/s12206-020-0738-7
Journal of Mechanical Science and Technology 34 (8) 2020 Original Article DOI 10.1007/s12206-020-0738-7 Keywords: · Circular cylinder · Natural convection · Power law fluid · Square enclosure
Unsteady characteristics of laminar free convection in an enclosure in the presence of power law fluid at Ra = 107 Sudhanshu Pandey1, Yong Gap Park2 and Man Yeong Ha1 1
Correspondence to: Man Yeong Ha [email protected]
Citation: Pandey, S., Park, Y. G., Ha, M. Y. (2020). Unsteady characteristics of laminar free convection in an enclosure in the presence of power law fluid at Ra = 107. Journal of Mechanical Science and Technology 34 (8) (2020) 3457~3470. http://doi.org/10.1007/s12206-020-0738-7
Received February 11th, 2020 Revised
May 10th, 2020
School of Mechanical Engineering, Pusan National University, 2, Busandaehak-ro 63beon-gil, Geumjeong-gu, 2 Busan 46241, Korea, School of Mechanical Engineering, Changwon National University, 20, Changwondaehak-ro, Uichang-gu, Changwon 51140, Korea
Abstract
The present study deals with an unsteady laminar free convection inside the annuli confined between an outer square enclosure and an inner circular cylinder. The annuli are filled with non-Newtonian power law fluids. The inner cylinder is located at three positions along the vertical center line. The unsteadiness arising due to bifurcation of flow from steady state is also reported in this study. The flow characteristics were found to be steady in nature in case of shear thickening fluid. However, most of the cases in the shear thinning fluid regime are found to be unsteady in nature with periodic and non-periodic fluctuations. The bifurcation of the flow from steady to unsteady state is mainly governed by the location of the cylinder as well as the characteristics of non-Newtonian fluid. The Bernard cells arising due to very high convective flow at Ra = 107 are also observed in the flow fields.
Accepted June 11th, 2020 † Recommended by Editor Yong Tae Kang
1. Introduction
© The Korean Society of Mechanical Engineers and Springer-Verlag GmbH Germany, part of Springer Nature 2020
The heat transfer mechanism in the presence of non-Newtonian fluids are still under active research due to its applications in many industrial and engineering applications such as large or small scale cooling or heating systems. The presence of internal body within an outer enclosure certainly enhanced the heat transfer performances in the thermal systems. Nevertheless, natural convection has been thoroughly investigated in the presence of Newtonian fluid. However, due to rising demand of non-Newtonian fluids in chemical or mechanical industries, it has become an area of interest for researchers across the globe. The rate of heat transfer enhances when an internal square cylinder is subjected to constant wall temperature heating in comparison to constant heat flux heating, as reported by De and Dalal [1]. Several numerical analyses focused on investigating the natural convection in the presence of an internal circular
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