Transition and Turbulent Drag Reducing Properties of Microfibrillated Cellulose and Papermaking Fibre Suspensions in Hagen Poiseuille Flow

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This work will shed light onto a longstanding problem in fluid mechanics, i.e. the transition to turbulence in pipe flow, through use of a novel visualization technique. Optical coherence tomography (OCT), a rapidly emerging technique, will be used in conjunction with confocal scanning laser microscopy (CLSM) and ultrasound Doppler velocimetry (UDV), to create detailed high-resolution spatial and temporal estimates of the flow field in the boundary layer. By doing so we will be able to estimate turbulence quantities and capture tomographic images of turbulent structures in the boundary layer and address fundamental questions such as (i) the relationship between rheology and apparent wall slip, (ii) the nature of the structure of the turbulent puffs and slugs in the boundary layer and (iii) the mechanism for turbulent drag reduction. Although this work has applications in a number of natural and industrial settings, the study is motivated from a pulp and paper application, namely the flow behavior of microfibrillated cellulose (MFC) and papermaking suspensions. The interest in MFC is dramatically increasing dramatically in both the scientific and commercial domains over the last decade. MFC has unique rheological properties and key to further development is a deeper understanding of the flow properties of this material. A five year project is proposed to be conducted by one PhD and one MASc student in either Chemical of Mechanical Engineering. The work will be primarily experimental, with some aspects of analysis of the OCT images.