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The present work concerns the heat transfer around a rigid cube inside either in air or in water. The fluid moves inside a channel and the cube is located at the center of the channel. The cube temperature is different from the temperature of the ambient fluid and a buoyant force acts on the cube. The Reynolds number varied between 0.01 and 100 and the Richardson number varied between -100 and 200. Both confined and unconfined flow is treated. Numerical predictions show that the Nusselt number is high in the opposing and assisting region and minimum around the forced convection. For Peclet numbers lower than 1 the Nusselt number is independent of the Richardson number and this is valid for any kind of rigid body placed in any kind of fluid.

The present work is an extension of a previous work published in Journal of Theoretical and Applied Mechanics (Chandrasekar and Kasiviswanathan, 2015). New results and analytical and asymptotic solutions are presented not found in the previous paper.

The steady laminar boundary layer flow over a stationary plate (Blasius flow) or in a moving plate (Sakiadis flow) with suction and in the presence of non-linear Rosseland radiation is investigated in this paper. When the suction varies in a special way the problem is similar whereas when the suction is constant 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, temperature parameter, radiation parameter and suction parameter and the influence of these parameters on the results are presented in tables and figures. It was found that two asymptotic states exist both in the similar and non-similar problem. The asymptotic temperature field in the similar problem has been calculated numerically whereas for the asymptotic temperature field in the non-similar problem analytical solutions have been found.

In a paper published recently in Journal of Heat Transfer (Feng [1]) the forced convective heat transfer from a heated rotating sphere in laminar flow was investigated numerically using a direct numerical simulation. There were significant discrepancies between [1] and previous studies. In the present paper we solved the same problem with another numerical method. The present fluid dynamics results are compared with the results of two previous numerical works and another experimental work and the comparison was very good. Afterwards the heat transfer problem was solved and we found large discrepancies between our results and those of Feng [1] which reach up to 38% for the isothermal case. New correlations for the mean Nusselt number for air have been developed for isothermal and constant heat flux case. The results for the heat flux case are new in the literature.

A serious error has been found in the above paper.

The present comment concerns some doubtful results included in the above paper.

The present comment concerns some doubtful results included in the above paper.

Two serious errors have been found in the above paper.

The present comment concerns some doubtful results included in the above paper.

This research undertook an assessment of the characteristics of laminar flow in a 90° bend. The research utilised the computational fluid dynamics software tool ANSYS Fluent, adopting a finite volume method. The study focused on pressure decreases, velocity profiles, Dean vortices and Dean cells present in the bend. The results indicated that the Dean vortices first appear slightly at the bend, take a clear form at the exit pipe and disappear further downstream. This article contains also an original chart for determining the Darcy–Weisbach friction factor, while the areas of pipe where Dean vortices and Dean cells formed are presented in a bifurcation diagram.

The natural convection along a vertical isothermal plate in a non-Newtonian power-law fluid is considered in this article. The problem has been treated in the past but only for the heat transfer case. The boundary layer equations are solved with the finite volume method. The problem is non-similar and is governed by the Prandtl number, the power-law index and the non-dimensional distance along the plate. Results are presented for non-dimensional distance up to 1000, Prandtl numbers from 1 up to 1000 and power-law index from 0.6 up to 1.5. Local Nusselt numbers, temperature profiles, skin friction and velocity profiles have been calculated and presented in tables and figures. The new results, combined with those existing in the literature, give a complete solution to this classical problem in the field of non-Newtonian power-law fluids.

The present comment concerns some doubtful results included in the above paper.

The flow of a non-Newtonian, power-law fluid, directed normally to long, two-dimensional horizontal bodies, is considered in the present note. It is found that for low Reynolds numbers ( Re ≤ 0.1 ) and a low power-law index (shear-thinning fluids) the drag coefficient always obeys the relationship c D = A / Re , whereas at a high power-law index (shear-thickening fluids) the drag coefficient tends to become identical for all bodies irrespective of their cross-section form.

The flow of a non-Newtonian, power-law fluid, directed normally to a horizontal cylinder with square cross-section (two-dimensional flow) is considered in the present paper. The problem is investigated numerically with a very large calculation domain in order that the flow could be considered unconfined. The investigation covers the power-law index from 0.1 up to 2 and the Reynolds number ranges from 60 to 160. Over this range of Reynolds numbers the flow is unsteady. It is found that the drag coefficient and the Strouhal number are higher in a confined flow compared to those of an unconfined flow. In addition some flow characteristics are lost in a confined flow. Complete results for the drag coefficient and Strouhal number in the entire shear-thinning and shear-thickening region have been produced. In shear-thinning fluids chaotic structures exist which diminish at higher values of power-law index. This study represents the first investigation of unsteady, non-Newtonian power-law flow past a square cylinder in an unconfined field.