Fundamental studies of plugging in multiphase flows with adhesive particles

This project considers a phenomenon we often observe at home when the tubes are plugged by sticky particles. A similar kind of plugging may occur in oil pipes leading to a huge economic loss and negative environmental effect. In addition, the particulate plugging of blood vessels is among the dominant reasons for stroke. In spite of the commonness of the plugging, this process is still not entirely understood. There are cases when a lot of particles safely flow in a pipe without leading to blockage; whereas even a trace amount of solids may shut the flow.To understand more about plugging, we reproduce this process in the lab using a new experimental facility that has been recently launched at Western Norway University of Applied Sciences. Computer models of the experiment help us to depict numerous interactions between the flow and the particles, and, to track how they bond together building the plug. In this project, we have obtained the following results: - a new experimental flow loop with a sticky suspension is built. We can establish and control plugging in a transparent test section of the loop. - an extension of computer models simulating particulate collisions in a flow with particles is developed. The new model has been applied to model the deposition of particles in biological flows. - new icy tracer particles with variable stickiness are developed for Positron Emission Tomography. The particles are non-toxic and may be potentially used to track flows in living organisms. - we conducted PET experiments using new tracers and found out that the ice particles become most adhesive at -1 C in decane. - a new numerical model of plugging in multiphase systems has been developed. The model is validated against our experiments. In 2022 we hosted a guest researcher from Ecoles des Mines in France. The researcher measured the viscosity of ice slurry we work with.

-

When the sticky particles are dispersed in a pipe flow they may agglomerate and deposit on the walls. In many cases this leads to formation of plugs that block the pipe. The problem is crucial for the processing industry as technological plugs lead to unwanted environmental and financial loss. Even more dramatically, plugs in blood vessels disorder hemodynamics, increasing mortality risk. Although plugging is common in daily life (e.g. sink clogging), the process is driven by complex inter-related phenomena and therefore is not entirely understood. This project, first of its kind, aims to investigate plugging by means of numerical modeling. In contrast to previous studies, the model, based on a revisited CFD-DEM principle, will accurately simulate attractive particulate interactions on "particle-by-particle" principle while being computationally intensive to reproduce a real-scale plug. The model will implement collisional schemes already developed by the applicant. The accuracy of the model will be verified with the high-resolution positron emission particle tracking technique (PEPT). An important advantage of the project is to elucidate plugging with PEPT, that has never been done before. Globally the project will provide a fundamental understanding of the influence of dimensionless flow parameters on the kinetics of plugging. Flow maps of the plugging regime are among the most important deliverables of the planned study. They will provide the Norwegian industry with a valuable tool for avoiding plug formation already at the design stage. This project will establish a new direction at HVL, aiming to increase levels of environmental safety and production efficiency for the Norwegian processing industry. This activity connects to our recently launched PhD program in engineering computing and builds a new inter-disciplinary research group in Western Norway, collaborating with already established researchers in Norway and abroad.