Fluid-structure interactions in pipeline systems

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Pipelines are commonly used for transporting fluids in a variety of engineering systems. Pipeline systems typically involve cavities, such as the internal corrugations of flexible pipes, valve seats and side branches in pipeline networks. Turbulent, separated flows that form across the cavity openings can couple with the acoustic waves, and the resulting resonant pressure oscillations can lead to noise, vibrations and ultimately fatigue failure of the pipeline. While acoustically-coupled flows have been the subject of many investigations, insight into the excitation mechanisms specific to various types of acoustic modes remains elusive. The proposed five-year research program will investigate the fundamental differences in the acoustic response of the pipeline systems associated with the global and the trapped acoustic modes. This new insight will be used to develop methods of passive and active control of the flow-induced vibrations (FIV) and to formulate reduced-order models for simulations of acoustic responses of engineering systems. Moreover, novel applications of the flow-induced acoustic excitation of pipeline-cavity systems, such as energy harvesting, will be explored in the course of the proposed research program. In addition to studying the fluid-structure interactions (FSI) leading to the pipeline failure, the proposed research program will also look into prediction of the dispersion of hazardous gas clouds in the vicinity of a leak from a pipeline. In particular, hazard assessment of CO2 pipelines is a necessary and integral part of the Enhanced Oil Recovery (EOR) and the Carbon Capture and Storage (CCS) processes. To date, safety aspects of CO2 transportation have not been adequately studied. Current efforts in CCS are largely focused on capture and storage facilities, while the transportation aspects received relatively little attention. Energy production in Canada was responsible for up to 253 Mt CO2 equivalent of greenhouse gases in 2010, representing 36% of its total emissions. Mitigating greenhouse gas emissions using CO2 sequestration is an important part of an efficient strategy aiming to significantly reduce greenhouse gas emissions. The proposed research program will address important safety issues that can impact the regulatory framework of a CO2 sequestration infrastructure. A better understanding of such issues is critical to public acceptance of sequestration technologies. The proposed research program aims to investigate and quantify the extent of hazardous gas concentrations in the vicinity of a leak from a high-pressure pipeline in a variety of scenarios (e.g. proximity to ground and other solid surfaces, with and without cross-flow, and various leak geometries). The proposed research is a combined experimental and computational investigation that is complemented by theoretical modeling. Fluid flow will be simulated by solving the unsteady Reynolds-averaged Navier-Stokes (URANS) equations, and a large eddy simulation (LES) approach will be employed for selected system geometries and inflow conditions. Formation of liquid droplets and solid particles will be modeled by solving an equation for the probability distribution function for the corresponding phase. Digital particle image velocimetry (PIV) will be used to measure velocity fields in physical experiments, and the results will provide insight into the structure of the acoustic source(s) in the pipeline and into the momentum transfer processes of the gas leaks. In order to quantify the 3D flow effects, a tomographic version of PIV will be implemented. In addition to velocity measurements, a technique of infrared planar laser-induced fluorescence (IR PLIF) will be developed to measure the concentration of the gaseous phase of the CO2.