Scientific Computing Invited Speaker: "Data-Driven Filtered Reduced Order Modeling"

Traian Iliescu

Department of Mathematics

Virginia Tech

## Abstract:

We propose a data-driven filtered reduced order model (DDF-ROM) framework for the numerical simulation of general nonlinear PDEs that are amenable to reduced order modeling. The novel DDF-ROM framework consists of two steps: (i) In the first step, we use explicit ROM spatial filtering of the nonlinear PDE to construct a filtered ROM. This filtered ROM is low-dimensional, but is not closed (because of the nonlinearity in the given PDE). (ii) In the second step, we use data-driven modeling to close the filtered ROM, i.e., to model the interaction between the resolved and unresolved modes. To this end, we use a quadratic ansatz to model this interaction and close the filtered ROM. To find the new coefficients in the closed filtered ROM, we solve an optimization problem that minimizes the difference between the full order model data and our ansatz. Although we use a fluid dynamics setting to illustrate how to construct and use the DDF-ROM framework, we emphasize that it is built on general ideas of spatial filtering and optimization and is independent of (restrictive) phenomenological arguments. Thus, the DDF-ROM framework can be applied to a wide variety of PDEs.