Влияние числа Рейнольдса на распределение пульсационной составляющей вихря скорости по сечению плоского канала

Based on the analysis of results from different authors using direct numerical simulations of the liquid flow in a flat channel, the effect of Reynolds number on the distribution of mean-square values of projections of a pulsed component of vortex velocity through the cross-section of a flat channel has been studied.

Теневая визуализация турбулентного обмена между вихревым кольцом и окружающей средой при различных плотностях жидкостей в вихре и вне его

The turbulent exchange between a vortex ring and the environment was observed using shadowgraph imaging of the process when the density of the fluid inside and outside of the vortex is different. The characteristic distance of turbulent exchange traversed by the vortex is determined, and the dependence of this distance on the vortex velocity and the related Reynolds number is established.

Dynamics of vortex–antivortex creation and annihilation in current-driven mesoscopic superconducting squares

In this paper, based on the time-dependent Ginzburg–Landau theory, we study the dynamics of vortex–antivortex (V–Av) pairs in a mesoscopic superconducting square with a small hole under applied bias currents. For the sample with a centered hole, a V–Av pair can nucleate at the hole edges and moves in opposite directions perpendicular to applied constant DC drive. The influence of the external magnetic field on the (anti)vortex velocity and the lifetime of V–Av pairs is mainly investigated. Different modes in the dynamical process of the V–Av collision and annihilation are identified. Moreover, in the case when the hole is displaced from the center of the square, the V–Av dynamics behaves quite differently from the symmetric case due to the shift of the V–Av creation point.

Application of Image Preprocessing on PIV Experimental Study of Wake Vortex Interactive Instability

A basic experiment study with a simplified wing model was carried out to introduce a opposite wake vortex by different sizes of spoilers. A PIV measurement was employed to obtain a two dimension wing wake vortex velocity field data of different spoilers in a water towing tank and confirm the existence of Reyleigh-Ludwieg instability in aircraft wake vortex. The image preprocessing is useful in PIV post-processing by comparing the three kinds of image preprocessing results with normal PIV image processing results.

Emergence of Kelvin-Helmholtz Instabilities in Gas Turbine Rim Cavities: A Parameter Study

In an earlier paper of the authors, the occurrence of the so called Kelvin-Helmholtz instabilities (KHI) near the rim cavity of a 1.5 stage gas turbine has been examined by the use of CFD methods. It is shown that the KHI’s occur, when the swirl component of the hot gas flow is very strong. Due to the fact, that a high swirl is produced by the guide vanes of the first stage, this matter concerns most common gas turbines. A further paper validated the CFD methods used and derived KHI parameters (vortex appearance, vortex periodicity and vortex velocity) of a splitter plate model. In the current study, essential parameters revealed by the analysis of a gas turbine rim cavity model are compared to the parameters extracted from the investigation of the splitter plate model and the potential linear theory of Turner. The rim cavity model is derived from a test rig of a 1.5 stage gas turbine. The blades and vanes have been removed from the computations. As main flow boundary conditions, surface averaged parameters are used. It is shown that a description of KHI developing in a rim cavity model is partly possible using splitter plate KHI characteristics and the potential linear theory of Turner as well. A mathematical approach is formulated, which can predict the vortex velocity of KHI’s in turbine rim cavities.