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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 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.

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 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.

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.

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.

This study focused on the large-scale vortex structures. The working section was a tangential vortex chamber with a cylindrical cross-section. The flow was swirled by tangential supply of fluid into the chamber, using 12 direct-flow rectangular nozzles. The design swirl parameter was equal to 6.6 and was determined based on the vortex chamber geometry. The Reynolds number was maintained equal to 30000. Quantitative measurements were realized with the use of the optical technique of laser Doppler anemometry. The results of optical measurements allowed determining main parameters of the vortex core for two basic modes of the vortex flow, including the central direct-flow vortex and the spiral vortex.

Longitudinal and tangential components of the mean velocity field inside the Ranque tube of square cross section are presented for a central longitudinal section. Measurements are carried at central plane over the entire tube, with 1-2 millimeter step in transverse direction and with 10 millimeter step along the tube. The data is presented in the form of velocity maps.

The vortex effect in Ranque-Hilch vortex tube was investigated. Being discovered by G.J. Ranque[1] in l928, the effect still has no adequate generally accepted physical explanation. One of the reasons is connected with the lack of reliable experimental data describing velocity and temperature distributions inside the vortex tube. The sensors mounted inside the vortex tube contribute conspicuous perturbation in the flow. Therefore, the new measuring methods should be searched that do not or slightly disturb the flow. For this purpose, optical techniques are the most suitable. In order to use optical methods the vortex tube with square section was applied. The flow kinematics investigation inside the Ranque-Hilsch tube was carried out using a laser Doppler anemometer (LDA) with an adaptive temporal selection of the velocity vector (LAD-056). The measurements of vector components of the swirling flow velocity were carried out in close to the hot output section of the Ranque-Hilsch tube at a working pressure ...

This experimental work is aimed at investigating the self-similarity of the local axial vorticity and azimuthal velocity in the tip vortices core in the wind turbine rotor wake. In the current work, the averaged local axial vorticity and azimuthal velocity profiles of the tip rotor vortex were measured. These profiles were tested to a self-similarity and compared with the Lamb-Oseen vortex.

This paper is devoted to experimental investigation of the interaction between the pair of precessing vortices in a tangential vortex chamber. The test section was the tangential vortex chamber with a cylindrical working area. The liquid was tangentially fed into the chamber through 12 rectangular nozzles. The swirl parameter varied in the range 0 ÷ 6.6, and the Reynolds number varied within 6000 ÷ 52000. On the basis of visualization materials the dependence of the precession frequency of the system of two vortices was obtained. For the quantitative investigation the optical methods of laser Doppler anemometry (LDA) and the Particle Image Velocimetry (PIV) were used. Information about vortices and recirculation zones was obtained from the optical measurements.

The vortex breakdown bubble in the confined flow generated by a rotating lid in closed containers with polygonal cross sections was analysed both experimentally and numerically for the height/radius aspect ratio equal to 2. The stagnation point locations of the breakdown bubble emergence and the corresponding Reynolds number were determined experimentally and in addition computed numerically by STAR-CCM+ CFD software for square, pentagonal, hexagonal, and octagonal cross section configurations. The flow pattern and the velocity were observed and measured by combining the seeding particle visualization and the temporal accuracy of laser Doppler anemometry. The vortex breakdown size and position on the container axis were determined for Reynolds numbers, ranging from 1450 to 2400. The obtained results were compared with the flow structure in the closed container of cubical and cylindrical configurations. It is shown that the measured evolution of steady vortex breakdown is in close agreement with the numerical results.