Numerical and Experimental Investigation of the Cavitating Flow Within Venturi Tube

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 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.

110th Anniversary: Comparison of Cavitation Devices Based on Linear and Swirling Flows: Hydrodynamic Characteristics

“…Similarly, changes to the geometry of Venturi devices also have a significant influence on cavitation behaviour 42 . The information on devices which combine rotational and linear flows is almost non-existent, although in a recent study on a cavitating Venturi Kozak et al 43 have highlighted the significant influence that the introduction of swirl can have on the cavitating flow structures. The primary objective of this work is for the first time, to compare cavitation devices based on linear flows (orifice and Venturi) and swirling flows (vortex diode) on a systematic basis.…”

Numerical study of unsteady cavitating flows with RANS and DES models

“…Cheng et al 29 also investigated the V&V procedures for tip-leakage cavitating flow. Kozák et al 30 numerically and experimentally investigated the cavitating flow through a Venturi tube with a swirl generator. The numerical approach with Kunz cavitation model and realizable k-ε turbulence model showed good agreement with the experiments.…”

Prediction of unsteady, internal turbulent cavitating flow using dynamic cavitation model

“…Therefore, a reduction of turbulent viscosity in the two-phase region was proposed to improve the modelling of the unsteady behaviour of sheet cavitation by Coutier-Delgosha et al (2003), which yield a realizable k-« model with modified turbulent viscosity term. This model was proved to be suitable for two-phase internal turbulent cavitating flows with detachment and circulation (Ashrafizadeh and Ghassemi, 2015;Brinkhorst et al, 2017;Koz ak et al, 2019;Koz ak et al, 2015). Therefore, the modified realizable k-« model is adopted as the turbulence closure model, as it better predicts the unsteady cloud shedding phenomenon.…”