Effects of Reynolds number on leading-edge vortex formation dynamics and stability in revolving wings

The mechanisms of leading-edge vortex (LEV) formation and its stable attachment to revolving wings depend highly on Reynolds number ( $\textit {Re}$ ). In this study, using numerical methods, we examined the $\textit {Re}$ dependence of LEV formation dynamics and stability on revolving wings with $\textit {Re}$ ranging from 10 to 5000. Our results show that the duration of the LEV formation period and its steady-state intensity both reduce significantly as $\textit {Re}$ decreases from 1000 to 10. Moreover, the primary mechanisms contributing to LEV stability can vary at different $\textit {Re}$ levels. At $\textit {Re} <200$ , the LEV stability is mainly driven by viscous diffusion. At $200<\textit {Re} <1000$ , the LEV is maintained by two distinct vortex-tilting-based mechanisms, i.e. the planetary vorticity tilting and the radial–tangential vorticity balance. At $\textit {Re}>1000$ , the radial–tangential vorticity balance becomes the primary contributor to LEV stability, in addition to secondary contributions from tip-ward vorticity convection, vortex compression and planetary vorticity tilting. It is further shown that the regions of tip-ward vorticity convection and tip-ward pressure gradient almost overlap at high $\textit {Re}$ . In addition, the contribution of planetary vorticity tilting in LEV stability is $\textit {Re}$ -independent. This work provides novel insights into the various mechanisms, in particular those of vortex tilting, in driving the LEV formation and stability on low- $\textit {Re}$ revolving wings.

The experience of use the bioactive coated intramedullary flexible nailiing in treatment of long bone fracture

The study concerns a new method of treatment of bone fractures of upper and lower limbs based on osteogenesis stimulation by intramedullary implants with bioactive organic hydroxyapatite (HA). The method decreases consolidation period of diaphyseal fractures to 2-4 times. A technology of osteosynthesis and bone formation dynamics at the fracture zone and around the implant is described.

Crack formation dynamics investigation of in a solid body under the surfactant influence

A method for estimating crack formation in a solid is proposed. The necessity the crack formation dynamics investigation is substantiated. Based on the Rebinder effect, a method for controlling the cracking nature using surfactants is proposed. The destruction by impact and explosion of samples pre-treated with water and surfactant is considered. It is established that pre-treatment of glass plates with surfactant solution shows a more uniform cracks distribution on impact, which may be the basis for the assumption that the surfactants use in blasting will significantly improve the crushing quality and reduce the oversized fractions yield. When examining the samples, which were saturated with surfactant solution, it is seen that the cracks system only increased after the explosion, small cracks appeared, which connect large ones. In the case of water use, we also see an increase in cracking, but it is not as intense and uniform as in the case of surfactants previous use. This result also confirms the fact that the pre-saturation of the medium with a surfactant solution before the pulse loads contributes to a more uniform crushing in the future and provides a basis for experiments on three-dimensional models in this direction.