Modeling and Simulations in Fluids
Institute for Computational and Experimental Research in Mathematics (ICERM)
September 7, 2024  September 8, 2024
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Saturday, September 7, 2024

8:30  8:45 am EDTCheck In11th Floor Collaborative Space

8:45  8:55 am EDTWelcome11th Floor Lecture Hall
 Brendan Hassett, ICERM/Brown University

8:55  9:00 am EDTOpening Remarks11th Floor Lecture Hall
 Tulin Kaman, University of Arkansas

9:00  10:00 am EDTSecond Order Phase Transitions11th Floor Lecture Hall
 Speaker
 James Glimm, Stony Brook University
 Session Chair
 Tulin Kaman, University of Arkansas
Abstract
Second order phase transitions describe in a macroscopic manner the decay of energy of a physical system Applied to fluid turbulence, they lead to a proof of existence of nonsmooth solutions for the NavierStokes equation, with the mathematical proof outlined here. Applied to YangMills quantum fields, they give rise to the mass gap, a Millenium Prize problem. Applied to cosmology and astrophysics, they support a novel explanation for dark matter and dark energy.

10:15  11:00 am EDT

11:00  11:40 am EDTExascale DNS and timedependent reduced order model of turbulent premixed ammonia/hydrogen jet flames for power generation11th Floor Lecture Hall
 Speaker
 Jacqueline Chen, Sandia National Laboratories
 Session Chair
 Tulin Kaman, University of Arkansas

11:55 am  12:35 pm EDTState Redistribution on Adaptive Mesh Hierarchies with Embedded Boundaries11th Floor Lecture Hall
 Speaker
 Ann Almgren, Lawrence Berkeley National Laboratory
 Session Chair
 Tulin Kaman, University of Arkansas

12:50  12:55 pm EDTGroup Photo (Immediately After Talk)11th Floor Lecture Hall

12:55  2:00 pm EDTLunch/Free Time

2:00  2:40 pm EDTHighorder finitevolume methods on locally structured grids: algorithms and software.11th Floor Lecture Hall
 Speaker
 Phillip Colella, Lawrence Berkeley National Laboratory
 Session Chair
 Jacqueline Chen, Sandia National Laboratories
Abstract
We will discuss current work on fourthorder accurate finitevolume methods for conservation laws on locallyrectangular adaptive grids, including discretization methods for mappedmultiblock coordinate systems, and the use of embedded domainspecific languages and runtime compilation for obtaining high performance and high productivity on CPU and GPUbased systems. We will illustrate the use of these methods for CFD calculations in spherical geometries.

2:55  3:20 pm EDTCoffee Break11th Floor Collaborative Space

3:20  4:00 pm EDTInverse LaxWendroff Procedure for Numerical Boundary Conditions11th Floor Lecture Hall
 Speaker
 ChiWang Shu, Brown University
 Session Chair
 Jacqueline Chen, Sandia National Laboratories
Abstract
When solving partial differential equations, finite difference methods have the advantage of simplicity, however they are usually only designed on Cartesian meshes. In this talk, we will discuss a class of high order finite difference numerical boundary condition for solving hyperbolic HamiltonJacobi equations, hyperbolic conservation laws, and convectiondiffusion equations on complex geometry using a Cartesian mesh. The challenge results

4:15  4:55 pm EDTFully resolved Simulations of Complex Multiphase Flows11th Floor Lecture Hall
 Speaker
 Gretar Tryggvason, Johns Hopkins University
 Session Chair
 Jacqueline Chen, Sandia National Laboratories
Abstract
Fully resolved simulations of multiphase flow have come a long way in the last two to three decades and we now routinely simulate flows where we fully resolve a large range of temporal and spatial continuum scales, at least for relatively simple disperse flows of bubbles, drops and solid particles. The challenges now are twofold: How to use the results to increase our ability to predict industrial scale flows and how to conduct direct numerical simulations of much more complex systems. Routine predictions usually require course models where the large scales are evolved deterministically, and small scales are included statistically. We will discuss strategies to coarsen results of fully resolved simulations of multiphase flows in a systematic way, retaining sharp interfaces, as well as initial efforts to develop models to evolve the coarse flow. We also discuss efforts to simulate more complex flows, including threephase liquidgassolid disperse flows where the solid particles are either hydrophobic or hydrophilic.

5:00  6:30 pm EDTReception11th Floor Collaborative Space
Sunday, September 8, 2024

9:00  9:40 am EDTEfficient Computation through Tuned Approximation11th Floor Lecture Hall
 Speaker
 David Keyes, King Abdullah University of Science and Technology
 Session Chair
 Gretar Tryggvason, Johns Hopkins University
Abstract
Numerical software is being reinvented to provide opportunities to tune dynamically the accuracy of computation to the requirements of the application, resulting in savings of memory, time, and energy. Floating point computation in science and engineering has a history of “oversolving” relative to expectations for many models. So often are real datatypes defaulted to double precision that GPUs did not gain wide acceptance until they provided in hardware operations not required in their original domain of graphics. However, computational science is now reverting to employ lower precision arithmetic where possible. Many matrix operations considered at a blockwise level allow for lower precision and many blocks can be approximated with low rank near equivalents. This leads to smaller memory footprint, which implies higher residency on memory hierarchies, leading in turn to less time and energy spent on data copying, which may even dwarf the savings from fewer and cheaper flops. We provide examples from several application domains, including a look at campaigns in geospatial statistics, seismic processing, genome wide association studies, and climate emulation that earned Gordon Bell Prize finalist status in 2022, 2023, and 2024.

9:55  10:20 am EDTCoffee Break11th Floor Collaborative Space

10:20  11:00 am EDTTurbulentlaminar patterns in wallbounded shear flows11th Floor Lecture Hall
 Virtual Speaker
 Laurette Tuckerman, Sorbonne UniversitĂ©
 Session Chair
 Gretar Tryggvason, Johns Hopkins University

11:15  11:55 am EDTGreen's function for a general system of hyperbolicparabolic balance laws with application11th Floor Lecture Hall
 Speaker
 Yanni Zeng, University of Alabama at Birmingham
 Session Chair
 Gretar Tryggvason, Johns Hopkins University
Abstract
We consider a general system of hyperbolicparabolic balance laws, which contains both second order dissipation (viscosity) and lower order damping. As dictated by physics, the viscosity matrix and the Jacobian matrix of the lower order term are usually rank deficient. We study the Green's function of its linearization around a constant equilibrium state. The Green's function is constructed using heat kernels along equilibrium characteristics directions and delta functions along frozen characteristics direction. A detailed error estimate is given in spacetime pointwise sense. Our result applies to polyatomic gas flows.

12:10  1:30 pm EDTLunch/Free Time

1:30  2:10 pm EDTConvection: Lord Kelvinâ€™s brilliant blunder11th Floor Lecture Hall
 Speaker
 Katepalli Sreenivasan, New York University
 Session Chair
 Ann Almgren, Lawrence Berkeley National Laboratory
Abstract
One of the three modes of heat transport is convection. This detail matters in many contexts: interior of the sun, interior as well as the atmosphere of the earth, nuclear cooling structures, and many engineering applications. For example, an improper understanding of convection inside the earth led Lord Kelvin to underestimate the age of the earth (as is well known) by a factor of a few hundreds. We discuss turbulent convection in this talk. In particular, we will examine its behavior at parameter values characteristic of geophysical and astrophysical problems, taking guidance from experiment, simulation, and theory.

2:25  2:50 pm EDTCoffee Break11th Floor Collaborative Space

2:50  3:30 pm EDTInterface dynamics in ideal and realistic fluids11th Floor Lecture Hall
 Speaker
 Snezhana Abarzhi, California Institute of Technology / University of Western Australia
 Session Chair
 Ann Almgren, Lawrence Berkeley National Laboratory
Abstract
Interface and mixing and their nonequilibrium kinetics and dynamics couple micro to macro scales, and are ubiquitous to occur in fluids, plasmas and materials, in high energy density regimes. Stellar evolution, plasma fusion, reactive fluids, purification of water, and nanofabrication are a few examples of many processes to which dynamics of interfaces is directly relevant. This talk presents the rigorous theory of the stability of the interface – a phase boundary broadly defined. We directly link the structure of macroscopic flow fields to microscopic interfacial transport, quantify the contributions of macro and micro stabilization mechanisms to interface stability, and discover the fluid instabilities never previously discussed. In ideal and realistic fluids, the interface stability is set primarily by the interplay of the macroscopic inertial mechanism balancing the destabilizing acceleration, whereas microscopic thermodynamics create vortical fields in the bulk. By linking micro to macro scales, the interface is the place where balances are achieved.

3:45  4:25 pm EDTStability and Instability of Characteristic Interfaces and Free Boundary Problems in Fluid Flows11th Floor Lecture Hall
 Speaker
 GuiQiang Chen, University of Oxford
 Session Chair
 Ann Almgren, Lawrence Berkeley National Laboratory
Abstract
We will discuss some recent progress of our research program in developing rigorous mathematical approaches, techniques, and ideas to analyze the nonlinear stability/instability of characteristic interfaces (including vortex sheets and entropy waves) and related free boundary problems for compressible fluid flows governed by the Euler equations and related nonlinear PDEs, and explore stabilizing mechanisms such as magnetic, relativistic, thermoelastic, and compressibility effects for the characteristic interfaces. We also discuss how the principle of maximum entropy provides an approach for determining the physical probability distributions of the turbulent flow in the presence of constraints on the mean energy, if time permits.

4:25  4:30 pm EDTClosing Remarks11th Floor Lecture Hall
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