Public defence in Engineering Physics, M.Sc. (Tech) Leevi Viitanen

Title of the doctoral thesis is "Rheological properties of structured complex fluids"

Opponent is Associate Professor Anniina Salonen, Paris-Saclay University, France

Custos is Professor Mikko Alava, Aalto University School of Science, Department of Applied Physics

The public defence will be organised in Otaniemi (Otakaari 1, lecture hall M1).

The dissertation is publicly displayed 10 days before the defence in the publication archive Aaltodoc of Aalto University

Electronic thesis

Press release:

The present work studies the rheology of liquid foams. The focus is in predicting single rearrangements of bubbles and tuning the flow behavior with external factors. The thesis helps understanding of foam flow on bubble scale and explores the modification of bubble motion and foam flow. The bubble rearrangements are analogous to structural rearrangements in other amorphous materials such as glasses, granular material and soft colloidal materials. The project succeeded in defining the structural features of foams that indicate local yielding. In addition, the research proved that external vibration enhances local yielding and, consequently, accelerates the foam flow. Also, study managed to simulate the effect of added nano-fibers on the flow of foam in a channel. Results of the present thesis may be applied in optimization of industrial processes that utilize foams. The results are useful, especially, for processes where the foam transports nano-fibers prepared for example from cellulose. The thesis concludes that the foam structure defines the time and location of local bubble rearrangements. These rearrangements then define the flow behavior of the entire foam.

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