Martin Hudec

Dynamics of the cavitating flow downstream of the orifice plate

Orifices with varying number of holes, but with the same flow cross-sections were tested in a cavitation circuit. Static characteristics, in term of loss coefficients, were measured in a range of non-cavitating and cavitating regimes. Since cavitating flow has very rich dynamics attention was also paid to spectral properties, especially in the cavitating regime. Data evaluated from several pressure transducers placed downstream of the orifice and for different orifice types are presented and discussed. Marked differences in both static and dynamic characteristics are observed between single-hole and multi-hole orifices.Orifices with varying number of holes, but with the same flow cross-sections were tested in a cavitation circuit. Static characteristics, in term of loss coefficients, were measured in a range of non-cavitating and cavitating regimes. Since cavitating flow has very rich dynamics attention was also paid to spectral properties, especially in the cavitating regime. Data evaluated from several pressure transducers placed downstream of the orifice and for different orifice types are presented and discussed. Marked differences in both static and dynamic characteristics are observed between single-hole and multi-hole orifices.

Investigation of the Cavitation Within Venturi Tube: Influence of the Generated Vortex

The main scope of the paper is evaluation of the experimental results and comparison of the dynamics of the vortex affected cavitating flow with the dynamics of purely axial flow within the Venturi nozzle. The analysis of the high-speed records with the sampling frequency of 20,000 images per second will be presented. Records will be analyzed using the proper orthogonal decomposition (POD) and spectral analysis of the pixel intensity within the selected region of images. These analyses will be done for the wide range of regimes for the both experimental configurations (with and without the swirl generator). Analysis of the pressure pulsations and vibrations will be utilized for the verification of the results. The cavitation patterns affected by the presence of the vortex will be described and compared with the case of axial inflow. The analysis of the experimental data will be complemented with the numerical computations of the chosen regimes carried out using the OpenFoam v1606+ and its multiphase interPhaseChangeFoam solver.

Numerical and experimental investigation of the cavitating flow within Venturi tube

December 16-21 2017 Abstract Hydrodynamic cavitation represents complex physical phenomenon undesirably affecting operation as well as lifespan of many hydraulic machines from small valves to the large hydro power plants. On the other hand, the same phenomenon and its concomitants such as pressure pulsations can be exploited in many positive ways. One of them which seems to be very promising and perspective is the cavitation utilization for reduction of the microorganisms such as cyanobacteria within large bulks of water. Mutual effect of the swirl induced by the upstream mounted generator and flow constriction in convergingdiverging nozzle has been experimentally investigated. The main scope of this paper is numerical investigation complementing the experimental results. The multiphase simulations were carried out using the OpenFoam 1606+ and its interPhaseChangeFoam solver. The present study focuses on CFD results of the cavitating velocity field within the nozzle and analysis of the loss coefficient within the nozzle.

Experimental investigation of check valve behaviour during the pump trip

The paper is focused on the description of an experimental investigation of a nozzle check valve. Attention is paid to the behaviour during transitions when the flow is decelerating. Flow reversal is often accompanied with the check valve slam, because the check valve closes with a delay after the flow changes its direction. The maximal back flow velocity determines the maximal pressure peak when the check valve closes, so this velocity was found for different flow decelerations.