Non-Newtonian Power-Law Flows around Circular Cylinder under Aiding/Opposing Thermal Buoyancy

Abstract

This paper presents a comprehensive computational work on hydrodynamic and thermal phenomena of upward flow separation around a confined circular cylinder by aiding/opposing thermal buoyancy. For that purpose, let us consider a confined flow of Non-Newtonian power-law fluid around a heated/cooled circular cylinder in a two-dimensional vertical channel. The effects of thermal buoyancy and power-Law index on the flow separation and the average Nusselt number are studied for the conditions: (10 ≤ Re ≤ 40), (0.4≤ n ≤ 1.2), (-0.5 ≤ Ri ≤ 0.8), Pr = 50 and blockage ratio β = 0.2. In the steady flow regime the results show that the augmentation of the power-law index in the absence of thermal buoyancy causes a separation to grow. The adding buoyancy effect delays the separation in different power-law indices gradually and at some critical value of the buoyancy parameter it completely disappears resulting a stuck flow around a cylinder, whereas the opposing buoyancy effect causes an earlier wake behind cylinder. Moreover, the recirculation length is calculated to support the above finding. The decrease in the power-Law index increases the heat transfer rate. The Nusselt numbers are computed to predict the heat transfer rates of power-law fluids under the aiding/opposing thermal buoyancy condition.

Simulation of Non Newtonian Power-Law Fluid Flows and Mixed Convection Heat Transfer inside of Curved Duct

“…In order to verify the numerical methodology, sets of comprehensive numerical tests are conducted to evaluate the accuracy of our results in comparison with other available numerical investigation of D. chatterjee et al [14] and Aboueian J. et al [15]. The results of validation are available at [13]. As presented in this paper, a good agreement is observed between present work and the previous researches.…”

“…In order to understand the effects of thermal buoyancy on Newtonian and non Newtonian fluid flow and heat transfer, Laidoudi H. et al performed a series of researches [11][12][13]. In the first work [11], the effect of superimposed thermal buoyancy as well as asymmetrically confined circular cylinder submerged in incompressible Poseuille liquid, this work is done only at fixed value of blockage ratio B = 20%, the governing equations of continuity, momentum and energy have been solve by the ANSYS-CFX Software.…”

“…Furthermore, increase in the value of Prandtl number enhances the heat transfer rate due to kinematic viscosity which represented as dissipative agent responsible for the eventual conversion of kinetic energy into heat. In the third study [13], the effects of thermal buoyancy and power-Law index on the flow separation and the average Nusselt number are studied for the conditions: (10 ≤ Re ≤ 40), (0.4 ≤ n ≤ 1.2), (0 ≤ Ri ≤ 0.8), Pr = 50 and blockage ratio β = 0.2. The Reynolds numbers of flow are chosen in low range such that the flow remains steady and separated without imposition of the thermal buoyancy.…”

The Effect of Asymmetrically Confined Circular Cylinder and Opposing Buoyancy on Fluid Flow and Heat Transfer

“…Recently, many research works are available in the literature that devoted for fluid flow and heat transfer around circular cylinder. The majority of these works emphasize on thermohydrodynamic characteristics of fluid subjected to aiding thermal buoyancy for flow around confined cylinder [4][5][6][7][8]. The principal parameter that controls a relative effect of buoyancy is the Richardson number Ri, defined as Ri = Gr / Re2, where, Gr is Grashof number, and Re is Reynolds number.…”

“…The Strouhal, Nusselt numbers are also calculated in this work. Laidoudi H. et al [6] they studied numerically the effect of aiding thermal buoyancy on the distribution of local Nusselt number around a confined square cylinder, a vertical Non-Newtonian flows of power low fluids are used in this word for this range of conditions: Re = 20, Ri = 0 to 0.5, n = 0.4 to 1.2. The results showed that, when the thermal buoyancy is superimposed, the recirculation zone disappeared at all behind the cylinder, and the local Nusselt number decreased behind the object.…”