Partial Differential Equations for Incompressible Fluids and Elastic Solids

The focus of this project is to study the behavior of fluids and elastic materials that are modeled mathematically by so-called partial differential equations. The aim is to further our understanding of certain phenomena by utilizing rigorous and quantitative mathematical results. Numerical simulations will also be used in parts of the project. The phenomena that will be studied are motivated by applications to real-life problems with potential societal impacts and are characterized by the presence of singularities and the coupling between different length and time scales. In the first part of the project, the exchange between walls and incompressible fluids will be considered by studying the effect of injection and suction on fluid flow and the effect of the motion of multiple bodies immersed in the fluid and their possible collisions, as in debris flow and sedimentation. In the second part of the project, the object of investigation will be how an incompressible flow transports and deforms directional objects, as in magnetic and conducting fluids, and the interplay between mixing and diffusion, as in biological processes. The last part of the project concerns modeling of faults buried deep in the Earth's crust and their monitoring using data from Global Positioning Systems (GPS) and satellites, with the ultimate goal of predicting the onset of seismic events. The project provides also training opportunities for graduate and undergraduate students, particularly members of under-represented groups.The focus of this project is the study of various problems modeled by partial differential equations concerning the behavior of incompressible fluids and elastic solids, using analytic and geometric techniques. The problems under investigation are motivated by fundamental physical phenomena and bring about challenging mathematical questions, such as fluid-structure interaction problems in the presence of collisions, and non-local and non-linear interface conditions for elastic dislocations. The project is divided into three main parts. The first part concerns the behavior of inviscid and slightly viscous fluids with boundary injection and suction, which can be used to control turbulent flows in pipes and channels and stabilize the viscous boundary layer. The motion of rigid bodies in a viscous fluid when slippage is allowed will also be studied, with applications to debris flow and sedimentation. The second part concerns measures of mixing and stretching for transport of vectors by a flow, such as in magneto-hydrodynamics, and enhanced dissipation for degenerate operators, with applications in electro- and thermo-rheological fluids and mathematical biology. The third part concerns seismic faults and fault monitoring using GPS and satellite data. Progress on these problems is likely to have impact in other fields, such as geophysics and engineering. The presence of multi-scale effects and singularities gives cohesiveness to the project. While its focus lies on analytic results and techniques, several of the proposed problems, such as optimal mixing and modeling of faults, have a natural computational counterpart that will be addressed together with collaborators.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.