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The effect of interaction between a vortex ring and a solid surface is experimentally and theoretically investigated. Analytical formulas are provided that allow describing the pressure pulses arising when the vortex ring passes near the flat surface. The forms of pressure pulses are compared with those recorded in the experiment. The results may be utilized to predict the off-design regimes of a hydraulic turbine; such regimes are characterized by aperiodic high impacts in the hydraulic turbine’s circuit behind the runner.

This article presents a comparative analysis of flow characteristics behind a hydraulic turbine runner in air and water. Swirling flow with a precessing vortex core (PVC) was investigated using a laser Doppler anemometer and pressure pulsation sensors. The experiments were conducted on aerodynamic and hydrodynamic test rigs over a wide range of hydraulic turbine operating conditions. Part-load modes of hydraulic turbine operation were investigated using the Fourier transform of pressure pulsations obtained from acoustic sensors. The features of the swirling flow were shown for the range of operating conditions from deep partl-load to overload.

Regularities of the vortex motion in an industrial glass bioreactor with a volume of 12 liters with a reactor vessel diameter D = 190 mm and with a filling of 50% was studied. A 65% water solution of glycerin was used as a model culture medium (density ρ g = 1150 kg/m3 and kinematic viscosity Vg = 15 mm2/s). Methods of particle image velocimetry and adaptive track visualization were used to observe the vortex pattern. The regularities of the vortex motion of the cultural medium were determined. It was found that, similar to the case of two rotating immiscible liquids, a strongly swirling jet was formed near the axis, and the entire flow took on the structure of a miniature gas-liquid tornado. The aerating gas interacted with the liquid only through the free surface, without mixing with it. As a result, the intensification of interphase mass transfer was provided due to the high speed of motion of the aerating gas.

Using digital processing of high-speed visualization data on a cavitation flow near NACA hydrofoil with critically low aspect ratio, the frequencies of the formation and separation of cavities in the flow are identified. It is shown that in the case of development of cloud cavitation the main dimensionless frequency varies within 0.4, which corresponds to the type of internal instability. The Strouhal number corresponds to the frequency of attached cavity occurrence and varies in range from 0.6 to 0.8. The Strouhal numbers calculated in third mode exceed 1. This mode corresponds to the forming of very small cavities near the leading edge of hydrofoil.

Current work deals with the study of swirling laminar flows in confined and unconfined flows in order to identify common patterns considering the phenomenon of vortex breakdown. Two types of vortex breakdown patterns are created: spiral and bubble. To catch the main flow features the modern tracer visualization technique adapted to experimental conditions is used. Measurements of velocity distributions are conducted via two-component LDA system. This work also confirms some ideas proposed by (Jones et al. 2015) about generalization of vortex breakdown conditions in different geometries.

An experimental investigation of the multiphase turbulent flow in a square vortex chamber was carried out to examine the self-oscillation of a cavitating cavity in a wide range of flow rates and pressure conditions. Such phenomenon is observed behind turbine runner when the hydraulic units operate at full load regime at high flowrate, and leads to significant flowrate and pressure pulsations in the entire hydraulic system. The dynamics of the cavity over time, and the freaquency of the volumetric oscillations frequency was studied via high speed visualization. The grey-scale images of the vortex cavity were binarized. By assuming an axially symmetric flow, the volume of cavity for each frame was integrated, and further investigated using FFT. Quantitative information on the structure of a single-phase flow was also obtained using the PIV technique.

This paper is devoted to experimental investigation of formation of precessing vortices pair in a vortex chamber with a cylindrical working area. Flow structure was registered by means of a high-speed visualization technique. Quantitative measurements characterizing the vortex properties were carried out using a 2D particle image velocimetry (PIV) technique synchronized with wall pressure measurements. The results show that two symmetrical precessing helical vortices are present downstream of the tangential nozzles.The phase- averaged analysis confirms the presence of large-scale twin vortex structure that visualized by small air bubbles dissolved in water.

Results of experimental modeling of a swirling flow in a Turbine-99 draft tube prototype are presented. The influence of gas phase injection into the flow has been studied. Experiments were performed on a closed hydrodynamic setup containing a working stage with the Turbine-99 draft tube geometry. It is established that the gas content affects the flow structure. Gas injection leads to a change in the frequency of precession of the vortex core formed in the draft tube cone, which is not related to an increase in the gas-liquid mixture flow rate.

Kelvin waves formed on precessing helical vortex tube after vortex reconnection were experimentally visualized. The experiments were performed in a swirling flow of viscous fluid in optically transparent conical diffuser. Vortex visualization was facilitated by cavitation in the vortex core and carried out using high-speed video cameras. Kelvin waves of zero, first and second modes m = 0, 1, 2 were formed in packets as a result of reconnection due to vortex tube self-intersection. Kelvin waves were observed to form both on the helical vortex tube and the detached vortex ring and to propagate along the axis of the vortex tubes.

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.