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Lagrangian tracking of the cavitation bubble
Bossio Castro, Alvaro Manuel ; Zatočilová, Jitka (referee) ; Rudolf, Pavel (advisor)
In this thesis, the dynamics of an isolated cavitation bubble submerged in a steady flow is studied numerically. A Lagrangian-Eulerian approach is considered, in which properties of the fluid are computed first by means of Eulerian methods (in this study the commercial CFD software Ansys Fluent 19 was used) and the trajectory of the bubble is then computed in a Lagrangian fashion, i.e. the bubble is considered as a small particle moving relative to the fluid, due to the effect of several forces depending on fluid's pressure field, fluid's velocity field and bubble's radius. Bubble's radius dynamics, modeled by Rayleigh-Plesset equation, has a big influence on its kinetics, so a special attention is given to it. Two study cases are considered. The first one, motivated by acoustic cavitation is concerned with the response of the bubble's radius in a static flow under the influence of an oscillatory pressure field, the second one studies the trajectory of the bubble submerged in a fluid passing by a Venturi tube and a sharp-edged orifice plate.
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Lagrangian tracking of the cavitation bubble
Bossio Castro, Alvaro Manuel ; Zatočilová, Jitka (referee) ; Rudolf, Pavel (advisor)
In this thesis, the dynamics of an isolated cavitation bubble submerged in a steady flow is studied numerically. A Lagrangian-Eulerian approach is considered, in which properties of the fluid are computed first by means of Eulerian methods (in this study the commercial CFD software Ansys Fluent 19 was used) and the trajectory of the bubble is then computed in a Lagrangian fashion, i.e. the bubble is considered as a small particle moving relative to the fluid, due to the effect of several forces depending on fluid's pressure field, fluid's velocity field and bubble's radius. Bubble's radius dynamics, modeled by Rayleigh-Plesset equation, has a big influence on its kinetics, so a special attention is given to it. Two study cases are considered. The first one, motivated by acoustic cavitation is concerned with the response of the bubble's radius in a static flow under the influence of an oscillatory pressure field, the second one studies the trajectory of the bubble submerged in a fluid passing by a Venturi tube and a sharp-edged orifice plate.
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Výpočetní analýza potenciálu kavitační eroze v hydraulickém stroji
Sedlář, M. ; Zima, Patrik ; Müller, M.
The paper describes a new model for efficient modeling of water cavitation erosion potential in turbulent cavitating flow. The number and size of the cavitation nuclei in the inlet flow are predicted empirically or experimentally using the acoustic spectrometer. The bubble dynamics is described using the Rayleigh-Plesset equation along the flow streamlines obtained from the 3D RANS equations. The model of the erosion potential is based on the estimation of the energy dissipated by the collapses of the cavitating bubbles. The paper also describes the experiment carried out in the cavitation tunnel in the SIGMA R&D Institute. The CFD model is tested for 2D and 3D geometry. It is shown that the erosion potential of the first collapses is several orders higher than the potential of the subsequent collapses. The numerically determined location and magnitude of the first collapses are compared with the photographs of the erosion pattern. The agreement for the tested cases is very good.
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Rozložení energie v kavitační bublině během jejího růstu a kolapsu
Müller, M. ; Maršík, František ; Garen, W.
Shock wave generation during the bubble growth and collapse and the corresponding energy separation were investigated experimentally. The calculation of the shock wave energy was based on the experimentally determined shock wave velocity profile. The possibility of using the similarity solution to determine the shock wave intensity is discussed. The velocity field around the collapsing bubble was visualized and compared with the numerical simulation using the commercial FLUENT code.
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