Irina Znamenskaya | Searcharxiv

arXiv2021

The dynamics of discontinuities in a cylindrical energy deposition based on a nanosecond discharge

The focusing of a secondary shock wave was experimentally recorded during the implementation of an extended nanosecond high-current discharge of a cylindrical configuration in air. Using high-speed shadowgraph recording (up to 300 000 frames/s) of the emerging unsteady flow, cylindrically symmetric gas-dynamic discontinuities were visualized: a diverging shock wave moving from the discharge plasma boundary, a diverging contact discontinuity separating the shock-heated gas from the nonequilibrium region excited by the discharge plasma, and also a converging compression wave (secondary shock wave) moving from the contact surface to the axis of symmetry and focusing on it 50-60 microseconds after discharge with the formation of a heated long-lived cord.

physics.flu-dyn↗

arXiv2021

Methods for panoramic visualization and digital analysis of thermophysical flow fields. A review

The paper presents a review of modern methods in the registration, processing, and analysis of dynamic processes in liquids, gases, plasmas, multiphase media, which are realized in researches and technology. The review author observes both the physical fundamentals of flow visualization and the basics of modern technologies for the digital processing of recorded flow images. A brief analysis of the panoramic visualization methods progress history covers a period of one and a half centuries. In the works of the last decade, the focus is on the methods of computer processing, tools, technologies for analyzing and recognizing panoramic thermophysical fields, which make it possible to obtain quantitative information about flows. The review contains an analysis of publications describing the main modern methods of visualization of flows: methods based on the phenomenon of refraction; electroluminescence; digital tracing (particle image velocimetry), visualization of surface flows (PSP and TSP coatings, liquid crystals; oil coatings). Particular attention is paid to methods using cross-correlation image processing algorithms. Those are: digital tracing (PIV), shadow background method (BOS), seedless shadow methods, thermographic PIV, velocity measurement in viscous coatings, micro, tomographic modifications of PIV, etc. The actual problem of digital data analyzing in a panoramic experiment is touched upon - the problem of big data. Examples of machine learning use in the analysis of big data sets of shadow surveys are given. Some examples of numerical simulation data visualization (simulation of experimental flowfields) are considered.

physics.flu-dyn↗