Search

The paper presents a software module for flexible configuration of a measuring system implements phase triangulation methods to measure three-dimensional profile of objects in aerodynamic experimental stands. To adjust and optimize a wide range of parameters of the measuring system, a universal solution has been implemented, that aimed to control of the operation of phase triangulation algorithms and binary Gray codes. To estimate the measurement error, an automated algorithm is implemented based on a statistical analysis of the distribution of the coordinates of the points of the measured surface.

The laser-Doppler anemometry method was developed for experimental studies on control of turning-and-diverging flow have been carried out; detailed diagnostics of averaged and turbulent characteristics have been made. Numerical modeling and comparison with experimental data based on known up-to-date turbulence models have been performed; comparative analysis of models has been done. The findings may be useful for determination of applicability limits of turbulence models.

The paper presents a method for calibration of a three-dimensional geometry measurement system based on the phase triangulation for measurements in the conditions of limited volume with optical signals refraction. The calibration algorithm implements calibration procedures directly in the measurement volume in the presence of all the limiting objects that cause optical signals refraction. The method is universal for various conditions of limiting volume with optical signals refraction. The developed calibration method was tested in the case the limiting volume in the form of a plexiglass tube with the transverse size of 200 mm ´ 200 mm and the wall thickness of 20 mm and the measurement volume of 100 mm ´ 100 mm ´ 100 mm. The accuracy of 12 microns was achieved in the measurement of flat object three-dimensional geometry.

The paper substantiates selection of boundary conditions for correct modeling of gas motion in a turning-and-expanding flow. The choice is based on comparison of calculation results and experimental data. Measurements of average and pulsation values of flow velocity were carried out by the method of laser Doppler anemometry. The numerical modelling was performed on the basis of known modern turbulence models: $$k$$ - $$\varepsilon$$ model and Reynolds stress transfer model. A comparative analysis of the models was done. The comparison was made for the surfaces of the axial velocity component in a cross section. The data obtained can be useful for determination of the limits of applicability of various turbulence models and for verifying CFD codes.

Experimental studies on control of turning-and-diverging flow have been carried out; detailed diagnostics of averaged and turbulent characteristics have been made. Numerical modeling and comparison with experimental data based on known up-to-date turbulence models have been performed; comparative analysis of models has been done. The findings may be useful for determination of applicability limits of various turbulence models.

The paper presents the results of CFD modeling of air flows in a gas distributor breadboard at the inlet of structured catalytic cartridges. The calculation results were used for modifying the gas distributor. Comparison of the experimental and calculated data yielded the most adequate model of turbulence; relationship between the boundary conditions and the accuracy of the modeling results was revealed. Recommendations for improving the distribution of gas flow rates in the selected gas distributor breadboard are formulated.

This article describes a technique for measuring the diameter of fuel pellets in the range of 7.5-8.3 mm and its use in the Geometric dimension control unit of the line for automatic control of the geometric dimensions of fuel pellets stacked on pallets. The principle of operation of the unit for controlling the geometric dimensions of pellets is based on measuring the diameter of a pellet from the photograph of the pellet shadow.

The present work investigates local flow structures and the downstream evolution of the core of helical tip vortices generated by a three-bladed rotor. Earlier experimental studies have shown that the core of a helical tip vortex exhibits a local helical symmetry with a simple relation between the axial and azimuthal velocities. In the present study, a self-similarity scaling argument further describes the downstream development of the vortex core. Self-similarity has up to now only been investigated for longitudinal vortices and it is the first time that helical vortices have become the subject of such an analysis. Combining symmetry arguments from previous studies on helical vortices with novel experiments and knowledge regarding the self-similarity evolution of the core of longitudinal vortices, a new model describing what is referred to as ‘helical self-similarity’ is proposed. The generality of the model is verified and supported by experimental data. The proposed model is important for fundamental understanding of the behaviour of helical vortices, with a range of applications in both industry and nature. Examples of this are tip vortices behind aerodynamic devices, such as vortex generators, and fixed and rotary aircraft, and in combustion chambers and cyclone separators.

A spectral method of detection of laser Doppler velocimeter signals in turbulent flows is proposed. The method is based on estimating the signal/noise ratio adapted to the width of the power spectral density of the signal and comparing its value with the recognition threshold. Numerical simulations show that the error of the signal/noise ratio estimates is 1% for different velocities of the turbulent flow. Physical experiments aimed at measuring turbulent aerodynamic processes show that the proposed method offers a possibility of eliminating the errors of calculating the mean value and the velocity deviation equal to 15 and 78% by means of eliminating the signals with low signal/noise ratios from the processing system. Application of the proposed method also ensures lower nonuniformity of the signal/noise ratio estimates than that ensured by the famous method developed by Tropea for a wide range of turbulent velocities.

Visualisation via video recording was carryed out in a Ranque-Hilsch vortex tube with a square cross-section. Video files were captured at recording speeds from 1000 to 10 000 frames per second. The best video files were obtained at a shooting frequency of 7600 frames per second with an input pressure of 1 bar. The video confirmed the presence of a double helix in the flow core in the second section of the tube. The video files showed the presence of a circulation zone between the flow core and the periphery, which is constantly changing over time. It can be clearly seen the angle at which the particles move in the peripheral flow.

The aim of the work was to develop a laser Doppler anemometry method for high-speed turbulent aerodynamic flow diagnostic. As a result, this allowed us to measure two projections of the velocity vector in the range of 0.1 - 400 m/s with a relative error not exceeding 0.5%. The measurement area was 0.1x0.1x0.5mm. The positioning device moved the measuring unit in the area of 250 x 250 x 250 mm with an accuracy of 0.1 mm. This method also provides the ability to measure local flow rate fluctuations.

The complex method of ultrasonic diagnostics of two-phase flows in a liquid metal medium is developed. It allows measuring the dynamic and structural characteristics of the floating inhomogeneity. A software and hardware complex that implements the proposed method is developed and tested for ultrasonic diagnostics of two-phase flows in water and liquid metal medium.

The aim of the work is to develop a laser Doppler anemometry method for diagnosing turbulent aerodynamic flows in the near wall region. This will enable measuring two projections of the velocity vector in the range of 0.001 … 400 m/s with a relative error not exceeding 0.1%. The measurement area is 0.1×0.1x0.5mm. The positioning device allows moving the measuring unit in the area of 250×250x250 mm with an accuracy of 0.1 mm. This method also provides the ability to measure local flow rate fluctuations.

This work aims at creating a universal software package for the development and testing of triangulation methods using structured lighting for measuring the three-dimensional geometry of objects in difficult ambient lighting conditions. As a result, a software package meeting the stated requirements is created. Lighting is based on the Fong model. A method for preloading objects is implemented to optimize the operation of the software package. An accelerated method for creating shadow maps is proposed and implemented. The developed software package is shown to successfully perform all required functions.

Current work is devoted to the development of a device for monitoring the dynamic shape of a power unit. The work is based on the FMCW method. The light source uses a low-coherence semiconductor laser diode. Signal processing is performed on an adapted Doppler processor. The paper describes the methods, hardware and signal processing algorithms.

In this work, a method for physicochemical and biological optical studies of the nanoparticles size distribution is developed. Its implementation in the LAD-079 spectrometer is described. The distinctive features of the LAD-079 spectrometer include the following. Multi-angle parallel measurements of static and dynamic light scattering, scattering angle from 0–180 degrees. Probing at three wavelengths with the ability to analyze the polarization activity of the sample (488 nm, 532 nm, 650 nm). Programmable precision thermostat with an error less than 0.1 °C in the range 0 ÷ +80°C with the possibility of building and software implementation of the experiment plan. Robust monobloc design of the spectrometer that does not require adjustments and a special optical table. The ability to measure the size of dispersed nanoparticles in low-transparent liquids.

This problem can arise in mechanics, chemistry, and catalysis in the mass transfer intensification. The mass transfer characteristics were measured in a controlled rotary-divergent flow. The laser Doppler anemometer was used for turbulent mass transfer diagnostics. The experimental investigation was the one used to verify the numerical calculations. The numerical simulation has shown the presence of a near-wall jet after a rotary device and the reverse flow zones formation. The model of Reynolds stress transfer more adequately describes the flow in range of flow rates from 50 to 250 Nm3/h than k-w turbulence model.

This chapter comprises the review of new methods of phase triangulation, which allow 3D geometry measurements under the conditions of arbitrary measured object surface light-scattering properties, varying measurement setting external illumination, and limited depth of field of optical elements of the source and receiver of optical radiation. The application of the proposed methods provides higher metrological characteristics of measuring systems and expands the functionality and the range of application of optical-electronic systems for geometric control in the production environment.

The paper presents an optical method for monitoring of transparent icing, which is applicable for remote monitoring of wind turbine blade icing. The method is based on the effect of total internal reflection of light. A point light source is formed on a wind turbine blade. When icing appears on the blade, a light circle is formed around the light source at the ice–air interface as a result of refraction and reflection of light beams; the observed size of the beam depends on the icing thickness. Using several light sources, the method enables field monitoring of icing on the wind turbine blades.

A new optoelectronic method of contactless measurement of the profile of the surface of large complexly shaped objects distinguished by a high degree of reliability and resistance to variations in the optical properties of the surface of objects over a broad range and to additive noise in the images is proposed. The method utilizes structurized illumination, phase triangulation, and identification of phase images with stepwise shift.

The work continues the work of the previous year. The mass transfer characteristics were experimentally analyzed in a rotary-divergent flow with inserted blades. The laser Doppler anemometer was used for turbulent mass transfer diagnostics. The experimental investigation was used to verify the numerical calculations. As in previous year the model of Reynolds stress transfer describes the flow in range of flow rates from 50 to 250 n.m3/h more adequately than the Spallart-Almares turbulence model.

In the field of fundamental metrology and ensuring the unity of measuring instruments, the role of optical information methods, systems and technologies of non-contact diagnostics of dynamic processes is extremely relevant. The profiles of the axial velocity component were measured in the working section of the secondary standard test rig for air flow speed. The flow kinematics inside the working section is studied using a laser Doppler anemometer (LDA) with an adaptive temporal selection of the velocity vector (LAD-08).

The sea spray, a typical feature of the marine atmospheric boundary layer, is one of the most uncertain factors among those controlling hurricanes and severe storms. To investigate how extremely strong winds tear off spray from wave crests, to classify such events, and to quantify the efficiency of the disclosed mechanisms, the high-speed wind-wave flume was constructed. For development of understanding of spray formation under hurricane wind condition the information about velocity distribution is required. The flow kinematics inside the wind-wave was studied using a laser Doppler anemometer (LDA) with an adaptive temporal selection of the velocity vector (LAD-08).

The analysis of current complex experimental investigation of the vortex tube with square cross section is made focusing on the criticality of the inner flow in the framework of the flow crisis concept. The criticality condition is proved to take place in the vortex tube by operating with LDA obtained velocity experimental data. As the measured axial velocity exceeds the calculated velocity of centrifugal elastic waves on the boundary between the longitudinal circulation zone and the near wall swirling jet, two scenarios are supposed possible for the transition of the supercritical state to a subcritical one, similar to the vortex breakdown in a swirling jet at its discharge into the quiet liquid volume: the mild oscillations or a series of hydraulic jumps become possible, leading to a flow pattern choke change with the transformation to heat of excess kinetic energy.

The work continues the work of the previous year. The mass transfer characteristics were experimentally analyzed in a rotary-divergent flow with inserted blades. The laser Doppler anemometer was used for turbulent mass transfer diagnostics. The experimental investigation was used to verify the numerical calculations. As in previous year the model of Reynolds stress transfer describes the flow in range of flow rates from 50 to 250 n.m3/h more adequately than the K-e turbulence model.

Results from an experimental assessment of the applicability of laser triangulators for measurements of the thickness of hot rolled product are presented. It is shown that phase inhomogeneities caused by strong temperature gradients introduce serious distortions into the optical signals of laser triangulators, which ultimately substantially increase the error.

The flow structure inside the Ranque vortex tube is investigated by LDA method. The mean velocity field is presented in the working channel of square cross-section at overpressures of 0.1 and 0.3 MPa. Two-dimensional mean velocity pattern is analyzed for the center longitudinal plane, and all the three velocity components all over the transverse coordinate are shown in three cross-sections of the working channel: near the guiding apparatus, in the center and near the hot exit

The present work examines the local structure and downstream evolution of both longitudinal vortexes behind the vortex generators and the helical tip vortices generated by the rotating 3-bladed rotor. Both wakes flow with the strong longitudinal or helical vortices have been studied by stereo PIV measurements in a wind tunnel or a water flume accordingly. The vorticity field was calculated from the measured velocity fields. The downstream development of vortex local cores investigates by using self-similarity scaling arguments and local helical symmetry tests simultaneously. It was analyzed Batchelor’s vortex and 2-D vortex with a helical vortex to use a combined vortex model of the helical self-similarly for a comparison with the experimental data. The experimental study of the shape of both vortices was carried out to describe the downstream development of the expanding vortex core by the new combined vortex model based on the experimental observations triggered by previous studies of wakes behind vortex generators and rotors. It was established that the local helical symmetry with a simple correspondence between the axial and azimuthal velocity in the cores exists in all cross-sections along of both longitudinal and helical vortices. It is also found that the averaged vorticity profiles inside the core of both vortices are self-similar. This knowledge is important for the fundamental understanding of the vortex flows, as well as for the aspect of applications, for which parametric descriptions can be substantially reduced in terms of required time and cost by easing engineering models.

The flow behind a model of a wind turbine rotor is investigated experimentally in a water flume using particle image velocimetry (PIV) and laser Doppler anemometry (LDA). The study performed involves a three-bladed wind turbine rotor designed using the optimization technique of Glauert (Aerodynamic Theory, vol. IV, 1935, pp. 169–360). The wake properties are studied for different tip speed ratios and free stream speeds. The data for the various rotor regimes show the existence of a regular Strouhal number associated with the development of an instability in the far wake of the rotor. From visualizations and a reconstruction of the flow field using LDA and PIV measurements it is found that the wake dynamics is associated with a precession (rotation) of the helical vortex core.

This problem can arise in mechanics, chemistry and catalysis in the mass transfer intensification. The mass transfer characteristics were experimentally analyzed in a controlled rotary-divergent flow. The laser Doppler anemometer was used for turbulent mass transfer diagnostics. The experimental investigation was used to verify the numerical calculations. The numerical simulation has shown the presence of a near-wall jet after a rotary device and the reverse flow zones formation. The model of Reynolds stress transfer adequately describes the flow in range of flow rates from 50 to 250 n.m3/h. The Spallart-Almares turbulence model fails to adequately describe the flow at all flow rates.

The complex technique using laser and video equipment in test conditions at the setups of the Laboratory of water turbines of the Leningrad Metal Plant has been developed to conduct laser measurements of velocity fields and video recording of cavitation phenomena based on the integration of the laser systems (“LAD - 0xx" and “Track-07 S”), created at the Kutateladze Institute of Thermophysics SB RAS (IT SB RAS) and JSC “IOIT.” The Doppler anemometer allowed to achieve experimental distribution of the circumferential, axial, and radial velocity components at each point along the radius of the suction tube cone section of test experimental setup which has give information about vortex structure in suction turbine. The developed PTV method is described. The investigation of cavitation behind the turbine blade at test setup at velocities of 8-10 m/s is presented.

The fundamental scientific problem of this kind arises in mechanics, chemistry and catalysis in the intensification of mass transfer. The turbulent mass transfer characteristics were analyzed experimentally in a controlled rotational-divergent flow. The laser Doppler anemometry was used for turbulent mass transfer diagnostic. The verification of numerical calculations by computational hydrodynamics has been carried out according to the results of experimental studies. Calculation of turbulent kinematic is build on solving of a system of continuity and the Navier-Stokes equations. The fluid is incompressible and isothermal. For averaged equations closure, semi-empirical turbulence models were used: the k-ε model of turbulence and the Reynolds stresses transfer model. The calculation has showed the existanceof a near-wall jet after a rotating device and the generation of reverse flow zones. Comparison with experimental data has shown that all models of turbulence adequately model the rotational-divergent flow only until the formation of flow gaps and the formation of reverse flow zones. The discrepancy with the experiment occurs while controlling the flow to equalize the velocity profiles.

The work is devoted to experimental investigation of the vortex effect in the Ranque-Hilsch tube using non-contact methods. The vortex tube, which consists of the slit-type swirler made as accelerating vortex chamber, a working channel with a square cross section, a radial diffuser at the hot outlet and a diaphragm at the cold one was used. For optical diagnostics, the vortex chamber (swirler) was equipped with optical windows. On the basis of measurements by the laser Doppler anemometry method, new experimental information about flow at the entrance of the Ranque-Hilsch vortex tube was obtained.

Such fundamental scientific problem arises in much industrial application. The turbulent fluid dynamic characteristics were analyzed experimentally in a rotary-divergent flow. The laser Doppler anemometry was used for turbulent mass transfer diagnostics. The verification of numerical calculations by computational hydrodynamics has been carried out according to the results of experimental studies. Verification has shown that turbulent models describe the rotational-divergent flow well only until generation of flow gaps and formation of recirculation zones.

The aim of the present paper is to obtain a better understanding of wakes generated by 2, 3 and 4 elements (disks and/or rotors) modeling an array of wind turbines in a wind farm. We here extend the results from our previous experimental model studies on the correlation between the behavior of the wake behind dual configurations of passive disks and active rotors to establish new knowledge regarding the wake development behind the 3rd and 4th rotor operating in a wake. To accomplish this, 2D PIV velocity measurements were carried out to investigate the flow properties upstream and downstream the tested rotors and discs in the array. The study also provides measured values of power and thrust coefficients of the model turbines using strain gauges installed directly on the rotors. The aim of the laboratory experiment is to provide data to calibrate and validate wake models for design and analysis arrays of wind turbines located in wind farms.

This work sufficiently appends and extends experimental investigation of flow structure downstream of the triblade turbine model, which was started in 2011. Shadow zones from blades were removed and a measuring zone was increased as a result of changing in optical system of PIV. These changes made possible to carry out measurements in much more far zone downstream the rotor model. As a result new features of flow were found out in near and far wake downstream the turbine. The estimation of turbine work efficiency on different work regimes was carried out due to tensometric measurements of rotor force characteristics. This data corresponds to assumptions and hypothesis of classical theories of rotors and to a form for the optimum blades designed by the BEM method

The modification of absorption optic method for diagnostics of the wave liquid film on the surface of a rotating disk was proposed. Inaccuracy of the method was estimated analytically and experimentally. The field measurements of liquid film thickness on a rotating disk were carried out.

An optical method of measuring the instantaneous transparent liquid film thickness, based on the effect of total internal reflection by the gas-liquid interface, is represented. A light circle whose diameter is proportional to the liquid film thickness and eccentricity is proportional to the slope gradient of the liquid film surface in the measurement region is formed around a small-size light source in the plane of vessel bottom. Using several light sources, the method allows measurement of the liquid film thickness field. The method is implemented in a multichannel meter of transparent liquid film thickness and curvature surface, with computer image processing.