Cavitation is one of the most interesting phenomena in area of fluid flow research. It can be observed in many different hydraulic systems and its effects can be very serious. Basic problem with cavitation is its observation. The main aim of the paper is to propose and evaluate the simple method allowing registration of the cavitation cloud shape, which will be financially and computationally undemanding. Therefore, the article presents the system registering the shape of cavitation cloud. It is based on the optoelectronic devices, i.e. lasers and photoresistors, as well as on the assumption that cavitation leads to diffusion of lasers light on the vapor bubbles. The experiment was performed for three cavitation inducers and two flow velocities. Obtained results shows that the shape of cavitation cloud is dependent on the inducer, but not on flow velocity. It can be concluded that the described optoelectronic system can be regarded as an inexpensive alternative to traditional methods of cavitation observation.
This work is devoted to determining the effect of mesh density and mesh type on cavitation cloud volume generated during the flow of water through the cavitation tunnel. The numerical analysis was carried out on a water model based on a cavitation tunnel located at the Institute of Water Problems of the Bulgarian Academy of Sciences in Sofia, used to test the resistance of construction materials to cavitation erosion. A numerical analysis is performed for four different types of grids: polyhedra, poly-hexcore, hexcore, and tetrahedral. These grids have five different maximum cell sizes: 0.0025, 0.0020, 0.0015, 0.0010, and 0.0005 m. A numerical analysis is performed using commercial CFD software ‒ i.e., Ansys Fluent 2023 R1. The Schnerr and Sauer cavitation model and the k-omega viscous model for shear stress transport (SST) are used. This paper analyzes the qualitative parameters of the quality of the grid, distribution of velocity, pressure, average cell volume, and volume of cavitation cloud consisting of 90% volume vapor fraction. Based on the numerical analyses, it is shown that the basis for obtaining accurate results of the CFD simulations is not only the qualitative parameters of the grid but also its density.
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