Research Projects

Vortex induced vibrations (VIV) of structures can lead to failure and damage of structures in many practical applications ranging from heat exchanger tubes to marine applications such as pipelines and oil rigs. In these flows, the periodic shedding of vortices from the cylinder provides an exciting lift force on the body, which can lead to flow induced (FIV) or vortex-induced vibrations (VIV) of the cylindrical structure. Recently, there has been growing attention to the possibility of two-phase cross-flow over cylindrical structures leading to flow-induced vibration (FIV) in different engineering fields, including industrial heat exchangers such as in nuclear power plants, and in offshore systems. Compared to the large number of studies on VIV in single phase flow, there are relatively few fundamental studies on two-phase vortex-induced vibrations, which can be quite different from the single-phase VIV due to the motions of the bubbles and their interactions with the body, shear layer and the wake vortices. The few studies on bubby VIV that exist are mostly in practical applications of heat exchangers that involves flow over a bundle of cylinders that makes the understanding difficult. In the present work, we will take a relatively simplified case of an isolated single cylinder subjected to a bubbly cross flow to help us better understand the mechanisms involved in bubbly VIV flows. In particular, the focus would be to understand how bubbles affect the formation of wake vortices and, further downstream, how bubbles are captured within the wake vortices, modulate them, and thereby lead to shifts in the vortex shedding frequency and the exciting loads on the body. The study will be done experimentally with investigations increasing in complexity from the relatively simple flow of a single bubble flow over a fixed cylinder to understand its motions and capture by the shear layers and wake vortices, to the more complex case of bubbly flow over an elastically-mounted cylinder.

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