University of Twente Student Theses


Lagrangian Trajectories Method with Bubble Dynamics for Cavitation Inception Predictions

Beelen, S.J. (2018) Lagrangian Trajectories Method with Bubble Dynamics for Cavitation Inception Predictions.

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Abstract:Sheet cavitation can be induced by free-stream nuclei. To track free-stream nuclei through a flow field, a Lagrangian approach is coupled with bubble dynamics. A symmetric half body in potential flow at zero incidence, showed the screening effect. Screening makes large bubbles pass over the leading edge low-pressure region, preventing cavitation inception. Scale effects of screening are determined by the equivalent Stokes number. Using the Kármán-Trefftz transformation, the flow around a non-symmetric foil at incidence is constructed. A bubble dynamics equation determines the growth of gas nuclei. In the equation of motion the Kelvin impulse is incorporated. Furthermore, contamination by surfactants yields the need for the history force. When the nucleus is in contact with the foil, the trajectory is described by an impact model. Screening effects do in this non-symmetric case not influence the effective nuclei spectrum, but is mainly determined by the stability. In viscous flow solutions the effect of the Saffman lift force was found to be prevented by the impact model. At this symmetric hydrofoil at incidence, screening does not influence the effective nuclei spectrum. Finally, a roughness element induces more growth, but cavitating gas nuclei are not the only mechanism for sheet cavitation inception.
Item Type:Essay (Master)
MARIN, Wageningen, Netherlands
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
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