An important part of an experiment or ongoing process is observation. In many fields of science and production, there is a great need for visual monitoring of the occurring process or its result [Irodov n.d.]. However, the inspection may be difficult or even unattainable due to the closed space in which the process under study takes place. One such example is vortex chambers, which serve to mix various gases and substances under pressure or at high temperatures. These are large chambers of a round or conical shape where everything that takes place inside is hidden from the direct view of the observer due to the need to seal the chamber itself. The operation principle of such chambers is based on the multiple circulations of a substance at high velocity in the cavity of the housing, where various substances can be supplied under pressure [Aronson et al. 2015].

We study the possibility of application of the methods of laser Doppler anemometry for the noncontact measurement of the velocity of moving media in various phase states. We mention the specific features of the conditions of application of laser Doppler anemometers and, in particular the fact that, in numerous cases there exist restrictions on the use of photomultipliers. With an aim to find an alternative to the classical photomultiplier of a laser Doppler anemometer, we study three types of photomultipliers: classical electric vacuum photomultipliers, silicon avalanche multipixel photomultipliers, and photomultipliers with microchannel plate. We performed physical experiments aimed at measuring the velocity of aero- and hydrodynamic flows by laser Doppler anemometers with photomultipliers of the indicated three types. Actually, we measured the velocities of a rotating glass disk, of an aerodynamic flow in a channel with rectangular cross section, of an aerosol flow, and of a flooded hydrodynamic jet. The accumulated experimental data are analyzed according to the criteria of evaluation of the quality (efficiency) of operation and the ranges of applicability of the specified photomultipliers. By analyzing the physical properties of the investigated photomultipliers, we clarify their efficiency characteristics in different experiments. The ranges of efficient applications of these photomultipliers are determined for a broad class of physical experiments. The obtained results are of high importance for the researchers involved in the study of aero- and hydrodynamic flows in which it is necessary to have accurate and reliable result of measurements of the flow velocity. The optimal choice of a photomultiplier for the laser anemometers makes it possible to increase the accuracy, simplify the procedure of collecting the experimental data, and to reduce the cost of the final equipment.

The article considers issues of improving the metrological characteristics of the phase triangulation method for measuring the three-dimensional geometry of objects. The stability of measurement results is shown to be affected by the nonstationarity of ambient lighting. A method is proposed for filtering data collected by a photodetector during measurements via the phase triangulation method under non-stationary lighting conditions. This method relies on the frequency analysis of collected data and their filtering according to the first harmonic amplitude in the frequency decomposition of the signal. The proposed method in the form of a filtering algorithm was experimentally tested in a measurement system implementing the phase triangulation method. The filtering results obtained via the developed method using the frequency analysis of collected data were compared with those obtained via the filtering method relying on the amplitude modulation analysis of signal intensity recorded by the photodetector. The comparative analysis of filtering results obtained using the two methods showed the higher effectiveness (by more than eight times) of the proposed filtering method. The study results can be useful in processing and analyzing experimental results, as well as contributing to the development of optical methods for measuring the three-dimensional geometry of objects.

1 Оптическая диагностика многолуночных планшетов с реагирующей смесью при производстве 1 Институт теплофизики им.С. С. Кутателадзе СО РАН, г.Новосибирск, Российская Федерация * e-mail:

44 В. В. Рахманов 1 *, В. Г. Меледин 1 , Г. В. Бакакин 1 , С. В. Двойнишников 1 Исследование влияния квадратурных демодуляторов лазерных доплеровских анемометров на погрешность определения скорости 1 Институт теплофизики им.С. С. Кутателадзе СО РАН, г.Новосибирск, Российская Федерация * е-mail:

A numerical algorithm for fast search of the initial phase shift on phase images with arbitrary stepwise shifts is proposed. The algorithm is based on finding the minimum deviation of the model function from the measurement results. The interval search method used directly in the proposed approach made it possible to significantly reduce the computational complexity of the algorithm. The paper presents the results of measuring a three-dimensional profile by phase triangulation methods using the proposed algorithm. The obtained results confirm the efficiency and high practical value of the proposed phase image decoding algorithm.

The research was devoted to the problem of measuring geometric parameters of ice by the method of phase triangulation in a limited volume with refraction of optical signals. This method served to develop an algorithm of measurement and calibration. It was expedient to take into account the reflective properties of ice and the conditions of external lighting, as well as to ensure a minimum error in measuring the geometric parameters of ice. For this purpose, software complexes to control the quality of the measuring system with current parameters and to calculate the geometric parameters of ice, as well as a software and hardware complex for measuring the geometric parameters of ice by the phase triangulation method in a limited volume with refraction of optical signals have been developed. The measuring system was configured for a measuring volume with characteristic dimensions 100×100×60 mm. A measurement error of 12 microns has been achieved. Experiments were carried out to measure the geometric parameters of ice formed on a cylindrical surface. The values of the local thickness of the ice and the statistical value of the thickness of 1.6 mm have been restored. The developed technologies may be used in experiments on an aerodynamic stand for the study of icing processes aimed at creating anti-icing methods in various fields of industry.

Способ фазового усреднения электронно-оптических сигналов1 Институт теплофизики им.С.С.Кутателадзе СО РАН, г.Новосибирск, Российская Федерация * e-mail:

Аннотация.В рамках задачи развития методов фазовой доплеровской анемометрии разработан метод исследования структуры интерференционной картины, образованной полупроводниковым лазерным доплеровским анемометром с дифференциальной оптической схемой и модуляцией 80 МГц.Описаны основные аппаратные модули используемых лазерных доплеровских анемометров «ЛАД-080».Для исследования интерференционной картины был создан стенд из двух лазерных доплеровских анемометров и мишени.Лазерные анемометры модер-

оптических элементов системы измерения трехмерной геометрии объекта методом фазовой триангуляции 1 Новосибирский государственный университет, г.Новосибирск, Российская Федерация 2 Институт теплофизики им.С. С. Кутателадзе СО РАН, г.Новосибирск, Российская Федерация

In this work, a method of low-perturbation temperature diagnostics in the Ranque–Hilsch vortex tube is developed. The method is based on scanning of temperature with a set of up to eight special small sensors. The temperature profiles were synchronously recorded in different cross sections of the vortex tube. Contour maps of temperature distribution have been constructed.

A method for adaptive statistical filtering of experimental data is proposed to reduce the measurement error of three-dimensional geometric parameters using phase triangulation methods. The method is especially promising for use under conditions of measuring surfaces with random light-scattering properties, a limited dynamic range of a photodetector, and random additive noise. The practical value and efficiency of the proposed approach in the processing of phase images is shown.

The temperature stability of the laser wavelength is an important characteristic of a laser Doppler anemometer with chromatic channel separation. This work presents experimental studies of the 660-nm wavelength shift of a semiconductor laser diode as a function of temperature and laser radiation power. It is established that the temperature drift of the wavelength lies within 0.2 nm/ ^∘ C. It is shown that the use of semiconductor diodes of this type in laser Doppler anemometers with chromatic channel separation is possible, but requires careful selection of optical filters.

The article presents the application of optical methods for measuring the parameters of three-dimensional objects. It also discusses strategies for decoding phase images in the presence of additive interference and a limited dynamic range of a photodetector. The existing methods for decoding phase images introduce nonlinear distortions and systematic error into the measurement results under such conditions. A phase triangulation method with statistical data filtering is proposed for measuring the three-dimensional profile of an object under random additive interference with a limited dynamic range of a photodetector, which avoids systematic distortions of the measurement results. The method is based on adaptive filtering and statistical analysis of the intensity distribution in the recorded phase images. The error of the method of decoding phase images was analyzed analytically using statistical data filtering and threshold filtering. The proposed method can decode data in systems for measuring three-dimensional geometry that implements the phase triangulation method.

Methods for filtering signals in three-component laser Doppler anemometers for separating signals in optical paths of complementary devices are considered. A method is proposed for suppressing the mutual influence of signals based on the use of monochromatic sources of optical radiation with close wavelengths and bandpass optical filters. The possibility of implementing the proposed method of signals optical filtering in three-component laser Doppler anemometers using modern semiconductor laser diodes and bandpass optical filters is shown.