Nonlinear model reduction is a critical component in the design process of control strategies for complex flows in the nonlinear regime. A Galerkin projection based on POD-modes is developed in this study that takes advantage of multiple bases for particular components of the governing equations. These bases are then linked by the Discrete Empirical Interpolation Method (DEIM) to ultimately arr...

Gravity waves arise in gravitationally stratified compressible flows at low Mach and Froude numbers. These waves can have a negligible influence on the overall dynamics of the fluid but, for numerical methods where the acoustic waves are treated implicitly, they impose a significant restriction on the time step. A way to alleviate this restriction is to filter out the modes corresponding to the...

Abstract. This paper analyzes compressible gaseous slip flow through a three-dimensional straight uniform rectangular microchannel, and reports a set of asymptotic solutions. By comparing the magnitudes of different forces in the compressible gas flow, we obtain a proper criteria to estimate the Reynolds and Mach numbers at the channel exit. We select two sets of Mach and Reynolds numbers and o...

In this paper we treat subjects which are relevant in the context of iterative methods in implicit time integration for compressible flow simulations. We present a novel renumbering technique, some strategies for choosing the time step in the implicit time integration, and a novel implementation of a matrix-free evaluation for matrix-vector products. For the linearized compressible Euler equati...

The focus of this effort is to produce a two dimensional inviscid, compressible flow solver using the Discontinuous Galerkin Finite Element approach. The Discontinuous Galerkin method seeks to project the exact solution onto a finite polynomial space while allowing for discontinuities at cell interfaces. This allows for the natural discontinuity capture that is required for a compressible flow ...

Large scale Monte Carlo simulations have been used to study long-time domain growth behavior in a compressible, two-dimensional Ising model undergoing phase separation. The system is quenched below the transition temperature from a random spin state, and we investigated the late-time domain size growth law, R(t) = A+Btn. For “lattice mismatched” systems, we found n = 0.224± 0.004 which deviates...

We give a uniform bound from below on the temperature for a variant of the compressible Navier-Stokes–Fourier system, under suitable hypotheses. This system of equations forms a mathematical model of the motion of a compressible fluid subject to heat conduction. Building upon the work of [A. Mellet and A. Vasseur, Monatsh. Math., 157 (2009), pp. 143–161], we identify a class of weak solutions s...

This paper presents the development of a 2D solver for inviscid and viscous compressible flows using the spectral difference (SD) method for unstructured grids with mixed elements. A mixed quadrilateral and triangular grid is first refined using one-level h-refinement to generate a quadrilateral grid while keeping the curvature of boundary edges. The SD method designed for quadrilateral meshes ...

Recent interest in region based image coding has given rise to graph coloring based partition encoding methods. These methods are based on the four color theorem for planar graphs, and assume that a coloring for a graph with the minimum possible number of colors will result in the most compressible representation. In this paper we show that this assumption is wrong. We show that there exist gra...

A numerical technique for the solution of the compressible flow equations over unstructured grids in a spherical reference is presented. The proposed approach is based on a mixed finite volume/finite element discretization in space. Equivalence conditions relating the finite volume and the finite element metrics in spherical coordinates are derived. Numerical simulations of the explosion and im...