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Entropy generation is an important aspect of modern thermal polymer processing optimization. Many polymers exhibit strongly non‐Newtonian effects and dissipation effects in thermal processing. Motivated by these aspects in this study, a numerical analysis of the entropy generation with viscous dissipation effect in an unsteady flow of viscoelastic fluid from a vertical cylinder is presented. The Reiner‐Rivlin physical model of grade 2 (second‐grade fluid) is used, which can envisage normal stress variations in polymeric flow‐fields. Viscosity variation is included. The obtained governing equations are resolved using implicit finite difference method of Crank‐Nicolson type with well imposed initial and boundary conditions. Key control parameters are the second‐grade viscoelastic fluid parameter (β), viscosity variation parameter (γ), and viscous dissipation parameter (ε). Also, group parameter (BrΩ−1), Grashof number (Gr), and Prandtl number (Pr) are examined. Numerical solutions are presented for steady‐state flow variables, temperature, time histories of friction, wall heat transfer rate, entropy, and Bejan curves for distinct values of control parameters. The results specify that entropy generation decreases with augmenting values of β, γ, and Gr. The converse trend is noticed with increasing Pr and BrΩ−1. Furthermore, the computations reveal that entropy and Bejan lines only occur close to the hot cylinder wall. [ABSTRACT FROM AUTHOR]

The present paper aims to visualize a Casson fluid flow over a vertical cylinder using entropy generation with heat and mass functions concept. The non-linear mathematical model is given by the highly time-dependent coupled equations and is solved by using finite difference method. Unsteady profiles of momentum, heat and mass transport coefficients as well as the steady-state flow variables are displayed graphically for distinct values of non-dimensional physical parameters arising in the system. The result of entropy generation parameter increases with rising values of Casson fluid parameter, and the reverse trend is noticed for Bejan number. [ABSTRACT FROM AUTHOR]

The present paper aims to investigate the effect of Prandtl number for unsteady third-grade fluid flow over a uniformly heated vertical cylinder using Bejan’s heat function concept. The mathematical model of this problem is given by highly time-dependent non-linear coupled equations and are resolved by an efficient unconditionally stable implicit scheme. The time histories of average values of momentum and heat transport coefficients as well as the steady-state flow variables are displayed graphically for distinct values of non-dimensional control parameters arising in the system. As the non-dimensional parameter value gets amplified, the time taken for the fluid flow variables to attain the time-independent state is decreasing. The dimensionless heat function values are closely associated with an overall rate of heat transfer. Thermal energy transfer visualization implies that the heat function contours are compact in the neighborhood of the leading edge of the hot cylindrical wall. It is noticed that the deviations of flow-field variables from the hot wall for a non-Newtonian third-grade fluid flow are significant compared to the usual Newtonian fluid flow. [ABSTRACT FROM AUTHOR]

In the present research article, the transient radiative free convective hydromagnetic Casson fluid flow past a vertical cylinder with entropy heat generation is analysed numerically. The mathematical model of this problem is constituted by highly time-dependent non-linear coupled equations and they are resolved by an efficient unconditionally stable implicit scheme. The time histories of average values of momentum and heat transport coefficients, entropy generation and Bejan number, as well as the steady-state flow variables are discussed for several values of non-dimensional parameters arising in the flow equations. The results indicate that entropy generation parameter and Bejan number upsurges with rising values of Casson fluid parameter, viscous dissipation parameter, group parameter and Grashof number, whereas the reverse trend is observed for radiation and magnetic parameters. Also, it is viewed that the variation of entropy and Bejan lines occurs in the proximity of the hot cylindrical wall only. Finally, a comparison between the Casson and Newtonian fluid is made based on the obtained numerical results of the present study and this has important implications in industrial thermal materials processing operations. [ABSTRACT FROM AUTHOR]