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 converging–diverging nozzle has been experimentally investigated. The analysis of the hydraulic losses in the wide range of the cavitation regimes has been done as well as the investigation of the pipe wall acceleration induced by the fluctuations of the cavitating structures. The dynamics of the cavitation was studied using the proper orthogonal decomposition (POD) of the captured video records. 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 computational fluid dynamics results of the cavitating velocity field within the nozzle and analysis of the loss coefficient within the nozzle. The results of the numerical analysis were utilized for the further discussion of the experimental results.

Simple example of CE is a jet blowing over convex surface. The jet could attach to the surface depending on geometrical configuration and character of the flow. Many practical applications involve near wall flows, and often in these applications of wall jets, the jet is injected at an angle to a solid boundary. Such examples can be seen in aircraft industry, energy devices (film cooling of turbine blades, gas turbine combustion chamber walls, jet exhausters, spraying devices, etc.) and many other areas. All of these devices have something in common; they were created using experimental research to assure their functionality. Design optimization is the only possible solution nowadays, as there is no proper theory to predict the CE. Finding universal description for such extensive problem cannot be expected, but there are some expectations to discover basic principles [1]. Our department is mainly focused on reduction of energy demand and improvement of functionality in devices for air conditioning and ventilation in buildings and vehicles. Particularly local ventilation in small spaces can be unpredictable because of air jet interaction with surfaces. Improvement and better control of CE for better distribution of air into the room can be made based on an analysis of wall jet physics character. Enhanced interior aerodynamics in vehicle cabs is important motivation for study of effect of different factors on the CE. This article is focused on experimental and CFD investigation of behaviour of a jet which is travelling around surface. The main goal was describe the influence of surface geometry and properties of jet on Coanda effect formation.

In this paper, the Vorticity Confinement method (VC) is presented for the calculation of flow field around a bluff body. The VC method was originally proposed by Fan et al. The aim of the method is to capture small-scale vortical structures efficiently. The presented study assesses the VC method (namely the first formulation, referred to as VC-1, which involves first derivatives of velocity), for external aerodynamics presented here on a well documented simplified car -Ahmed bluff body with different slant angles, namely 25° and 35°. These slant angles were chosen because the 35° slant angle supports the boundary layer separation and therefore stronger wake (also stronger oscillations of the wake), while at the 25° slant angle no separation takes part and the wake is much weaker and also more stable. The VC method was applied using different values for the diffusion parameter and confinement

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Abstract. Large Eddy Simulation of backward-facing step flow laden with particles were performed. The number of particles is chosen very large and the volume fraction of particles is high enough for consideration of two-way coupling. This means that the particles are influenced by fluid and vice versa. The inter-particle collisions are neglected. The Euler-Lagrange method is adopted, which means that the fluid is considered to be continuum (Euler approach) and for each individual particle is solved Lagrangian equation of motion. Particles are considered to be spherical. The simulations are performed for different mass fractions of 90 µm glass particles. The results are compared to the single-phase flow in order to investigate the effect of the particles on the turbulence statistics of the carrier phase.