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The aim of this comment is to point out three major errors in the paper Akolade et al. (2024). [ABSTRACT FROM AUTHOR]

The flow induced by a sphere rotating inside an incompressible, non-Newtonian, power law fluid has been investigated numerically. The rotating sphere is enclosed in a concentric cubic box with solid boundaries. The fluid power-law index varied between 0.2 and 2 thereby covering both shear-thinning and shear-thickening fluids and the Reynolds number varied between 0.01 and 10,000. Numerical predictions show significant differences between shear-thinning and shear-thickening fluids. In the first case the flow is confined near the sphere whereas in the second case the flow extends up to the box plates. In creeping flow and shear-thinning fluids the torque is independent of the Reynolds number. [ABSTRACT FROM AUTHOR]

Some errors exist in the above paper. [ABSTRACT FROM AUTHOR]

The present comment concerns some doubtful results included in the above paper. [ABSTRACT FROM AUTHOR]

The steady laminar natural convection along a vertical isothermal plate with linear or non-linear Rosseland radiation is investigated in this paper. The problem is self-similar and the results are obtained with the direct numerical solution of the governing equations. This problem is governed by the Prandtl number, the temperature parameter as well as the radiation parameter, and the influence of these parameters on the results are presented in tables and figures. A new radiation parameter is introduced which leads to an asymptotic state. It is found that the temperature profiles take a special S-shape form with an inflection point. Moreover, it is shown that when the wall shear stress increases the wall heat transfer decreases and vice versa. [ABSTRACT FROM AUTHOR]

Abstract: The steady laminar boundary layer flow along a vertical stationary plate with convective surface boundary condition is investigated in this paper. The heat transfer coefficient is considered either constant or variable along the plate and the problem is either non-similar or similar. The results are obtained with the direct numerical solution of the governing equations. The problem is governed by Prandtl number and a convective parameter and the influence of these parameters on the results are presented in tables and figures. There are differences in the results between the non-similar and similar case at low values of the convective parameter but as this parameter increases the differences decrease and the flow tends to the classical natural convection along a vertical isothermal plate. [Copyright &y& Elsevier]

Abstract: The steady laminar boundary layer flow over a perforated plate, in the presence of suction, moving in a parallel stream with constant velocity is investigated in this paper. The temperature boundary condition on the plate is a convective condition. In contrast to the majority of the previous works, in the present paper the heat transfer coefficient and the suction velocity are constant and the problem is non-similar. The results are obtained with the direct numerical solution of the governing equations. The problem is governed by Prandtl number, the Biot number, the velocity ratio parameter and a streamwise parameter and the influence of these parameters on the results are presented in tables and figures. It was found that the temperature reaches an asymptotic state and an analytical solution has been found for the calculation of wall temperature at the asymptotic state. [Copyright &y& Elsevier]

Abstract: Computational Fluid Dynamics (CFD) methods are employed in order to simulate the 3D hydrodynamics and flow behaviour in a sedimentation tank. Unlike most of the previous numerical investigations, in the present paper the momentum exchange between the primary and the secondary phase is taken into account, using a Lagrangian method (discrete phase model) with two-way coupled calculations. By computing particle trajectories the proposed numerical model can track the momentum gained or lost by the particle stream that follows that trajectory and these quantities can be incorporated in the subsequent continuous phase calculations. Thus, while the continuous phase always impacts the discrete phase, the effect of the discrete phase trajectories on the continuum can be incorporated. This interchange affects fluid velocity, especially in the case of large particles sizes, which have a greater relaxation time in relation to the characteristic time of the tank. The present investigation compares a series of numerical simulations for a sedimentation tank with varying particle diameters and volume fractions, in order to identify the influence of the secondary phase to the primary phase and vice-versa and the way that this influence affects the efficiency of the tank. [Copyright &y& Elsevier]

Abstract: The flow of a fluid directed normally to a heated flat plate of finite length (two-dimensional flow) is considered in the present paper. Three cases are considered: i. both sides of the plate are heated at the same uniform temperature. ii. The upper side is heated uniformly while the lower side is insulated (upward facing plate). iii. The upper side is insulated while the lower side is uniformly heated (downward facing plate). The problem is investigated numerically with a finite volume method using the commercial code ANSYS FLUENT. The governing parameters are the Reynolds number, the Richardson number and the Prandtl number and the influence of these three parameters on the drag coefficient, the average Nusselt number and the wake length is investigated for all the considered cases. It is found that the drag coefficient, the Nusselt number and the wake length in the downward facing plate is always greater than that in the upward facing plate, for all the examined values of the Richardson, Reynolds and Prandtl number. The vertical centerline velocity above the plate and above the wake increases continuously and finally becomes identical with the velocity of a two-dimensional plume while the vertical velocity below the plate shows a maximum and then goes to zero. At very high Prandtl numbers (Pr → ∞) the buoyancy force near the plate tends to zero and the drag coefficient as well as the wake length approach asymptotically the corresponding values of pure forced convection. [Copyright &y& Elsevier]

Abstract: The flow of a laminar wall jet along either a moving plate, or in a free stream, or in combined moving plate and free stream is considered. The plate is isothermal and its temperature is different from that of the ambient fluid. The governing boundary-layer equations are converted into non-dimensional form and are solved numerically. Velocity and temperature profiles as well as the variation of wall shear stress and wall heat transfer are presented for all cases considered. For the case of a moving plate new results have been found although this problem has been investigated in the past. For the case of the free stream and the combined moving plate/free stream all the results are new and are presented for the first time in the literature. The three cases have been tackled with a unified way. [ABSTRACT FROM AUTHOR]

Abstract: The flow of a laminar wall plume in a constant transverse magnetic field is considered. The results are obtained with the numerical solution of the governing equations and cover both small and large ξ values and Prandtl numbers from 0.01 to 100. The similar wall plume has been investigated in the past but the nonsimilar has not been treated until now and it is solved here for the first time. [Copyright &y& Elsevier]

Abstract: The concept of boundary layer flow, introduced in 1904 by Prandtl, is a popular field in Fluid Mechanics for engineers, physicists and mathematicians. The present work is a critique to many papers published in the last 15 years in the field of boundary layer flow. The critique concerns the shape of velocity, temperature and concentration profiles which are truncated due to small calculation domain used during the numerical solution procedure. These truncated profiles are not compatible with the boundary layer theory and introduce errors in wall shear stress and wall heat transfer values. [Copyright &y& Elsevier]

Abstract: This work is a critique to a paper published in the International Journal of Heat and Mass Transfer 48 (2005) 4460–4466, which concerns the boundary layer flow of an electrically conducting incompressible fluid over a heated stretching sheet. The flow is permeated by a uniform transverse magnetic field and the fluid viscosity is assumed to vary as a linear function of temperature. In the published paper the calculation domain was small and the temperature profiles are truncated. Although the dynamic viscosity has been considered a function of temperature and consequently variable inside the boundary layer the Prandtl number, which depends on viscosity, has been considered constant inside the boundary layer. The results of the present work are obtained with the direct numerical solution of the boundary layer equations taking into account both viscosity and Prandtl number variation across the boundary layer. The temperature profiles of the present work are quite different from those of the above work. [Copyright &y& Elsevier]

One of the target of the above paper is the study of the entropy generation (it is included in the title). However, two serious errors exist in the study of entropy generation. [ABSTRACT FROM AUTHOR]

Abstract The present comment concerns some doubtful results included in the above paper. [ABSTRACT FROM AUTHOR]

Abstract The present comment concerns some doubtful results included in the above paper. [ABSTRACT FROM AUTHOR]

Abstract: In the latter years the title problem has been examined in a large number of research papers. The present Note emphasizes, however, that the effect of thermal radiation in the linearized Rosseland approximation is quite trivial, both physically and computationally. Namely, it always reduces to a simple rescaling of the Prandtl number by a factor involving the radiation parameter. This implies that a comprehensive study of the Prandtl-number dependence without thermal radiation effects represents per se a detailed study of the radiation effects, too. In other words, the solution of the radiation problem for optically thick media in the linearized Rosseland approximation does not require any additional numerical or analytical effort compared to the same problem without radiation, making in this respect dozens of papers superfluous. [Copyright &y& Elsevier]

A serious error exists in the above paper. [ABSTRACT FROM AUTHOR]

In the above paper some equations are wrong. [ABSTRACT FROM AUTHOR]

• The comment concerns a paper published in Chemical Engineering Science Journal. • The problem is non-similar. However the authors treated the problem as similar. • In non-similar problems one x-dependent parameter is used. The authors used three. [ABSTRACT FROM AUTHOR]

Two mistakes exist in [1]. [ABSTRACT FROM AUTHOR]

The present comment concerns some doubtful results included in the above papers. [ABSTRACT FROM AUTHOR]

This communication concerns some doubtful results included in the above paper. [ABSTRACT FROM AUTHOR]

The present comment concerns some doubtful results included in the above paper. [ABSTRACT FROM AUTHOR]

The present comment concerns some doubtful results included in the above paper. [ABSTRACT FROM AUTHOR]

The present comment concerns some doubtful results included in the above paper. [ABSTRACT FROM AUTHOR]

The present comment concerns some doubtful results included in the above paper. [ABSTRACT FROM AUTHOR]

Abstract: In the present comment we point out some weak points found in the above paper. [Copyright &y& Elsevier]