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Wednesday, November 03, 2021
09:00 AM - 10:00 AM
WebEx

Seminar

Convex optimization-based structure preserving filtering for polynomial-based numerical methods

Vidhi Zala
University of Utah

With the advent of numerical simulations, mathematical models can visualize real-world processes, predict results, save resources, and aid research and development by cutting costs and time. The popular choice of numerical methods for solutions to mathematical models includes the finite-element methods (FEM) and the finite-volume methods (FVM). These methods use polynomial-based projections to approximate the design space and solve the discretized version of the problems. In converting a continuous, real-world problem to a numerically solvable one, a significant hurdle is the approximation of the structure and prop- erties of the domain accurately. The problem of structure-preservation is essentially finding a robust and optimal solution to the constraints satisfaction problem while retaining the accuracy, convergence, and conservation properties (e.g., mass or flux). The solution proposed is an elegant convex-optimization based algorithm that is agnostic to problem-types, function spaces, polynomial orders, or numerical methods and guarantees structure-preservation throughout the whole domain.

The design ideology of this research is such that a particular structure of solution or a set of structures can be preserved simultaneously by transforming the problem into a convex- minimization problem. The solution is then obtained using an iterative approach based on a novel geometric intuition that involves conversion from the original solution space, which does not preserve the structure, to a corresponding feasible space where the structure is preserved. The entire process can be summarized as applying a filter to a structurally non-conforming intermediate solution and obtaining a solution that preserves the desired structure. Experi- mental data from the applications to discontinuous and continuous Galerkin finite element methods show the efficacy of this method to preserve the underlying structure during the simulation.

The major contributions of this research are the robust formulation of the structure-preservation problem, establishing convexity and solvability of the general formulation, developing elegant optimization algorithms to solve it, and applying the filtering approach to real-world problems. This is achieved while retaining the accuracy and the convergence properties of the numerical method in a non-intrusive way. Since this work is agnostic of the type of problems, polynomial order (space of the solution), types of structural constraints, or the numerical method used to solve the problem, the algorithm developed can be applied to ubiquitous polynomial-based solutions of various systems of PDEs.

Host: Svetlana Tokareva