Valeria Barra

California Institute of Technology | CIT · Division of Geological and Planetary Sciences

Dynamical cores used to study the circulation of the atmosphere employ various numerical methods ranging from finite‐volume, spectral element, global spectral, and hybrid methods. In this work, we explore the use of Flux‐Differencing Discontinuous Galerkin (FDDG) methods to simulate a fully compressible dry atmosphere at various resolutions. We sho...

This paper describes the use of flux-differencing stencils for the discontinuous Galerkin (FDDG) method for the compressible Euler equations with buoyancy. We use FDDG to solve nonhydrostatic atmospheric test cases of interest to the climate community (e.g., the Held-Suarez test case) using no additional dissipation mechanism except for that introd...

The influence of fluid-fluid interfacial properties on the dynamics of viscoelastic thin liquid films bounded above by liquid-liquid interface and below by a horizontal solid plate is studied in this work. The present study allows for integration of both chemical and physical properties of the thin liquid film within the long wave approximation of...

This work presents a novel numerical investigation of the dynamics of free-boundary flows of viscoelastic liquid membranes. The governing equation describes the balance of linear momentum, in which the stresses include the viscoelastic response to deformations of Maxwell type. A penalty method is utilized to enforce near incompressibility of the vi...

This work presents a study of the interfacial dynamics of thin viscoelastic films subjected to the gravitational force and substrate interactions induced by the disjoining pressure, in two spatial dimensions. The governing equation is derived as a long-wave approximation of the Navier-Stokes equations for incompressible viscoelastic liquids under t...

Finite element analysis of solid mechanics is a foundational tool of modern engineering, with low-order finite element methods and assembled sparse matrices representing the industry standard for implicit analysis. We use performance models and numerical experiments to demonstrate that high-order methods greatly reduce the costs to reach engineerin...

To cool electronic components of spacecraft, engineers are considering the use of heat pipes, which are sealed copper pipes containing an annular copper wick saturated with water. Water vapor from the hot end travels to the cold end, where it condenses in the wick and flows back to the hot end. In space, the cold end can freeze the water inside, wh...

Efficient exploitation of exascale architectures requires rethinking of the numerical algorithms used in many large-scale applications. These architectures favor algorithms that expose ultra fine-grain parallelism and maximize the ratio of floating point operations to energy intensive data movement. One of the few viable approaches to achieve high...

In this paper we describe the research and development activities in the Center for Efficient Exascale Discretization within the US Exascale Computing Project, targeting state-of-the-art high-order finite-element algorithms for high-order applications on GPU-accelerated platforms. We discuss the GPU developments in several components of the CEED so...

Efficient exploitation of exascale architectures requires rethinking of the numerical algorithms used in many large-scale applications. These architectures favor algorithms that expose ultra fine-grain parallelism and maximize the ratio of floating point operations to energy intensive data movement. One of the few viable approaches to achieve high...

Soft materials such as rubber, elastomers, and soft biological tissues mechanically deform at large strain isochorically for all time, or during their initial transient (when a pore fluid, typically incompressible such as water, does not have time to flow out of the deforming polymer or soft tissue porous skeleton). Simulating these large isochoric...

libCEED is a new lightweight, open-source library for high-performance matrix-free Finite Element computations. libCEED offers a portable interface to high-performance implementations, selectable at runtime, tuned for a variety of current and emerging computational architectures, including CPUs and GPUs. libCEED’s interface is purely algebraic, fac...

The main goal of this milestone was to help CEED-enabled ECP applications, including ExaSMR, MARBL, ExaWind and ExaAM, to improve their performance and capabilities on GPU systems like Summit and Lassen/Sierra. In addition, the CEED team also worked to: add and improve support for additional hardware and programming models in the CEED software comp...

The goal of this milestone was the performance tuning of the CEED software, as well as the use and tuning of CEED to accelerate the first and second wave of targeted ECP applications. In this milestone, the CEED team developed optimization techniques and tuned for performance the CEED software to accelerate the first and second wave target ECP appl...

As part of its discretization mandate, CEED is developing adaptive algorithms for mesh refinement, coarsening and parallel rebalancing needed in general unstructured adaptive mesh refinement (AMR) of high-order hexahedral and/or tetrahedral meshes. This milestone provides an update on our developments of adaptive mesh control methods for both confo...

In this milestone, we created and made publicly available the second full CEED software distribution, release CEED 2.0, consisting of software components such as MFEM, Nek5000, PETSc, MAGMA, OCCA, etc., treated as dependencies of CEED. The release consists of 12 integrated Spack packages for libCEED, mfem, nek5000, nekcem, laghos, nekbone, hpgmg, o...

This work presents a study of the interfacial dynamics of thin viscoelastic films subjected to the gravitational force and substrate interactions induced by the disjoining pressure, in two spatial dimensions. The governing equation is derived as a long-wave approximation of the Navier-Stokes equations for incompressible viscoelastic liquids under t...

It is imperative to cool electronic components of spacecraft in order to ensure their continued performance. One possibility for cooling such components is the use of heat pipes, which use the heat capacity of a working fluid to dissipate heat. In the case we analyze, these devices consist of a copper pipe (sealed at both ends) with an annular sint...

This dissertation is developed in the field of Computational Fluid Dynamics (CFD) and it focuses on numerical simulations of the dynamics of thin viscoelastic films in different settings. The first part of this dissertation presents a novel computational investigation of thin viscoelastic films and drops, that are subject to the van der Waals inter...

This executive summary complements a presentation of results given at the 33rd Annual Mathematical Problems in Industry (MPI) Workshop in Newark, NJ on June 23, 2017. Revon Systems has designed an expert system, delivered via a smart phone app, that provides recommendations to users on what action is appropriate given reported symptoms related to c...

This technical report examines the process by which sensor data from a region suspected to contain landmines is used to determine a set of alarm sites, including the manner in which the alarm set provided is scored against competing algorithms. The work and recommendations based on it were developed during the Mathematical Problems in Industry Work...

This study is developed in the field of Computational Fluid Dynamics, focusing on thin films and drops of viscoelastic liquids, such as polymeric fluids. The aim in this study is to give a full mathematical analysis and to provide numerical simulations for the moving interface of viscoelastic liquids. We are interested in the instabilities that cau...

This study is developed in the field of Computational Fluid Dynamics, focusing on thin films of viscoelastic liquids, such as polymeric fluids. Polymeric liquids combine characteristics of viscous fluids with features typical of elastic matter. They are present in a broad variety of real life aspects and therefore studied and used by a wide spectru...

Many technological applications are imposing increasing tight specifications on manufacturing processes in orderto construct high-precision products that are thinner, lighter, and more inexpensive. In the context of producinglarge video displays, there is a need to produce very thin glass sheets and identify any imperfections that can causedeviatio...

We numerically study the interfacial dynamics and instability of a thin viscoelastic film on a substrate. We use the long wave approximation to describe the non-linear evolution of the interface. We consider different regimes of slippage, and in each regime, we investigate the role of the liquid viscoelasticity and of the contact angle on the thin...

We study the linear stability of a thin viscoelastic liquid film under the influence of van der Waals interaction. The Jeffreys model is used to describe the viscoelasticity effects with a relaxation time and a retardation time. We study the governing thin film approximation that describes the nonlinear evolution in time of the interface in the lon...

We study the linear instability of a thin viscoelastic liquid film under the influence of van der Waals interaction. The Jeffreys model is used to describe the viscoelasticity with a relaxation time and a retardation time. We use the thin film equation that governs the nonlinear evolu-tion of the interface and study the linear stability of the inte...