This paper presents a numerical investigation of mixed convection heat transfer around a pair of identical circular cylinders placed in side-by-side arrangement inside a square cavity of single inlet and outlet ports. The investigation provided the analysis of gradual effect of aiding thermal buoyancy on upward flow around cylinders and its effect on heat transfer rate. For that purpose, the governing equations involving continuity, momentum and energy are solved using the commercial code ANSYS-CFX. The distance between cylinders is fixed with half-length of cavity. The simulation is assumed to be in laminar, steady, incompressible flow within range of following conditions: Re = 1 to 40, Ri = 0 to 1 at Pr = 0.71. The main obtained results are shown in the form of streamline and isotherm contours in order to interpret the physical phenomena of flow and heat transfer. The average Nusselt number is also computed and presented. It was found that increase in Reynolds number and/or Richardson number increases the heat transfer. Also, aiding thermal buoyancy creates new form of counter-rotating zones between cylinders.

The basic definitions and a history of the development of biomimetics as a discipline that considers nature-inspired design are presented in this paper. The discussion and the results of the application of principles of nature-inspired design in machine elements design are given. The fact that transition zones that Nature chose and designed on trees in many cases survived for more than a hundred years, resisting on the various and variable external loads and other external conditions, is considered. Presented case study used the nature-inspired transition shapes in the research of innovative design and geometric optimization of transition zones of high-loaded shafts. The comparative Finite Element Analysis is performed for a particular transition zone with traditional engineering design, as well as with nature-inspired design. The conclusions about the increase of load capacity that is obtained with innovative biomimetics design are discussed.

A generalization of the smeared concept for field problems, published in recent papers of the author and his collaborators, is presented in the paper. A composite smeared finite element CSFE is formulated. This generalization can serve as a theoretical background for further applications. A selected numerical example, related to convective-diffusive mass transport within a cancerous tissue, illustrates efficiency and accuracy of the smeared models. Further, a smeared methodology is extended to mechanical problems. A theoretical background is given in detail, with introducing a composite smeared finite element for mechanics CSFEM, which can further be tested and modified. Finally, a consistent derivation is presented for the continuum constitutive tensor corresponding to a fibrous structure.