Preface

The conference “Optical Methods of Flow Investigation” (OMFI) has been regularly held since 1989 at intervals of 2 years. The All-Union Seminar was held in 1989, I and II All-Union Conferences (founder – Institute of Thermal Physics of the Siberian Branch of the Russian Academy of Sciences) was held in 1991 and 1993. Since 1995, conferences have been held at the Moscow Power Engineering Institute (MPEI) under the auspices of the Siberian Branch of the Russian Academy of Sciences and the Ministry of Education of the Russian Federation, the co-founders were MPEI and the Institute of Thermophysics of the Siberian Branch of the Russian Academy of Sciences. Since 2019 Scientific and Technological Center of Unique Instrumentation of the Russian Academy of Sciences has also become a co-organizer of the conference. This issue of the Journal is devoted to research and studies presented at the XVI International Scientific and Technical Conference “Optical Methods of Flow Investigation” (OMFI-2021). The conference was held in Moscow Power Engineering Institute, Moscow, Russia, on 28 June – 02 July 2021. The National Research University “Moscow Power Engineering Institute” is one of the leading technical universities in Russia having about 15,000 students from more than 60 countries. MPEI is one of the largest technical universities in Russia. It provides the specialist’s training and scientific research in the field of energy, electrical engineering, radio electronics, computer engineering. The conference brought together experts from different organizations to initiate discussions on topics that are of interest to the conference attendees. The conference papers presented in the following areas: laser anemometry, flow visualization, development of quantum-optical devices, computer methods of signal and image processing, laser and optical interferometry, application of optical methods, acousto-optics and optoacoustic, optical methods in biomedicine and ecology, also included papers of the Youth workshop «Modern Methods of Flow Investigation – 2021». List of Organizing and program committees of the conference are available in this pdf.

Comparative Analysis of Three Algorithms for Two-Channel Common Frequency Sinewave Parameter Estimation: Ellipse Fit, Seven Parameter Sine Fit and Spectral Sinc Fit

Comparative Analysis of Three Algorithms for Two-Channel Common Frequency Sinewave Parameter Estimation: Ellipse Fit, Seven Parameter Sine Fit and Spectral Sinc FitIn this paper, a comparison analysis of three different algorithms for the estimation of sine signal parameters in two-channel common frequency situations is presented. The relevance of this situation is clearly understood in multiple applications where the algorithms have been applied. They include impedance measurements, eddy currents testing, laser anemometry and radio receiver testing for example. The three algorithms belong to different categories because they are based on different approaches. The ellipse fit algorithm is a parametric fit based on the XY plot of the samples of both signals. The seven parameter sine fit algorithm is a least-squares algorithm based on the time domain fitting of a single tone sinewave model to the acquired samples. The spectral sinc fit performs a fitting in the frequency domain of the exact model of an acquired sinewave on the acquired spectrum. Multiple simulation situations and real measurements are included in the comparison to demonstrate the weaknesses and strong points of each algorithm.

Measurement of Velocities in Two-Phase Flow by Laser Velocimetry: Interaction Between Solid Particles’ Motion and Turbulence

In this work, an experimental method based on laser anemometry with Doppller effects is developed. This allows the measurement of velocities and their fluctuations in a flow of solid-liquid suspension in an ascendant vertical pipe. In order to distinguish between the signals coming from the continuous phase, water, and those of the glass bead particles larger than the Kolmogorov length scale, an electronic logic circuit was incorporated in the measuring equipment. This enabled the study of both the slip velocity of the solid-liquid suspension and the influence of the large particles on turbulence. The results show that a fine particle suspension, which represents a tracer, behaves as a homogeneous fluid. For large particles, we confirmed the existence of a slip velocity and the effect of particle size on the turbulence. The use of two distinct measurement volumes produces good results for the direct measurement of the turbulent length scales. The results show that the presence of solid particles modifies the turbulence characteristics.