Many fluids in science and engineering (listed below) are vesicular particle suspensions that exhibit complex non-Newtonian rheological behavior during both bulk fluid flow and during flow through porous media. The complexities of such fluids? flow behavior cannot be captured by standard Navier-Stokes equations and are the result of microscale particle, bubble, and liquid interactions during deformation. Limited knowledge connecting these microscale interactions to resultant macroscopic behavior restricts attempts to infer flow processes from (field) observations and to predict the behavior of these fluids in natural settings or in engineered processes. The objective of the proposed research is therefore to numerically model the deformation and flow of a variety of dense, vesicular particle suspensions by reproducing 1) individual particle and bubble interactions at the microscale, 2) representative elementary volume behavior at the macroscale, and 3) larger fluid flow processes on laboratory and field scales. This objective will be achieved by first developing a numerical simulator for fluid flow and suspended inclusion (particles, bubbles) motion, and then employing these simulations, as well as thermomechanical methods, to derive physically viable, large-scale continuum-mechanical models, that account for the effects of microscale particle, bubble, and liquid interactions. The simulator will be a hybrid computer code that combines a fluid flow code with a code to model the motion of particles in dry granular materials. The predictive capabilities of the hybrid code and the derived continuum-mechanical models will be tested against analogue material and remelt experiments as well as against analytic solutions where available.
Many important flow phenomena in the sciences and in engineering are the result of the complicated flow behavior of dense, vesicular particle suspensions that lie in between fluids and solids, sometimes called slurries. Examples of processes that involve slurries include flow of magma in volcanic conduits affecting volcanic eruption dynamics (explosive versus effusive) and heat transfer with implications for the assessment of volcanic hazards and renewable geothermal energy resources. Other geoscience applications include landslides, mud flows, and lahars that also represent mixtures of liquids, particles, and (sometimes) bubbles with implications for the assessment of geohazards and (human-made and natural) environmental impacts. Specific flow behaviors of slurries also play an important role in biological and medical processes such as blood flow through veins or microbe transport in groundwater. Engineering applications of this project may include food, foam, cement, gel, and ceramics processing. The research proposed here aims at developing a computer code to simulate particle and bubble interactions in slurries at a very small scale to determine how the bulk substance deforms and flows and how it conducts gases. Insights gained at small scales are then up-scaled to the actual spatial and temporal scale of interest. This approach is difficult but important, because small-scale interactions of inclusions (particles, bubbles) have a large effect on the complicated (non-Newtonian) flow behavior of these fluids, where the otherwise often-invoked Navier-Stokes equations can typically not be employed. Therefore, predicting the flow behavior of dense slurries, based on their inclusion properties, has the potential to significantly impact science and engineering dealing with such non-standard, but often encountered and important, fluids. In addition, this project supports a postdoctoral researcher and, through interactions in laboratories, undergraduate and graduate students, who receive interdisciplinary training in mathematical, computer, material, and geophysical science. The developed computer code is expected to be of interest to numerous science and engineering disciplines.
