UBC Theses and Dissertations
A unified variational framework and applications for flow-induced vibration in cavitating flows Kashyap, Suraj
In this work, we present the development of a new computational framework based on the stabilized variational finite element methods for unsteady cavitating flows and application to flow-induced vibrations of freely oscillating hydrofoils. The ultimate goal is to build a robust and accurate high-fidelity framework for the computational study of the coupled multiphase fluid-structure dynamics and noise reduction of marine propellers. The first part of this work involves a delineation of the systematic development and testing of the new computational framework. We propose novel linearizations of the governing cavitation partial differential equations (PDEs) for numerical modeling. Numerical challenges arising due to the particular characteristics of two-phase cavitating flows and fluid-structure interaction are addressed. We demonstrate the ability of the numerical implementation to accurately capture prominent features of cavitating flows such as bubble collapse, steady and unsteady partial cavitation, cavity shedding, and re-entrant jet formation. The second part focuses on the application of the developed computational framework for flow-induced vibrations of freely oscillating hydrofoils with unsteady partial cavitating conditions. The interaction dynamics of the hydrofoil with the fluid forces are represented as an elastically mounted rigid body. A frequency lock-in mechanism of the unsteady cavity and vortex shedding to a sub-harmonic of the structural natural frequency is observed to sustain high-amplitude transverse oscillations of the hydrofoil. This exploratory work paves the way for the coupled multiphase hydroelastic interaction of propellers with the target of noise mitigation by active or passive control mechanisms.
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