Brandon Morgan
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View article: Evaluation of probability density function descriptions for three-component Rayleigh–Taylor mixing
Evaluation of probability density function descriptions for three-component Rayleigh–Taylor mixing Open
View article: Atwood effects on nonlocality of the scalar transport closure in three-dimensional Rayleigh-Taylor mixing
Atwood effects on nonlocality of the scalar transport closure in three-dimensional Rayleigh-Taylor mixing Open
The importance of nonlocality is assessed in modeling mean scalar transport for turbulent Rayleigh-Taylor (RT) mixing at different Atwood numbers. Building on the two-dimensional incompressible work of Lavacot et al. (2024, JFM), the prese…
View article: Shock tube simulations for the three-layer Richtmyer–Meshkov instability with single-mode and multimode perturbations
Shock tube simulations for the three-layer Richtmyer–Meshkov instability with single-mode and multimode perturbations Open
While the canonical two-component, single-mode Richtmyer–Meshkov instability (RMI) has been extensively studied, relatively less work has focused on the effects of an additional intermediate-density middle layer. This work investigates suc…
View article: Development and assessment of models for turbulent Rayleigh-Taylor mixing using the macroscopic forcing method
Development and assessment of models for turbulent Rayleigh-Taylor mixing using the macroscopic forcing method Open
View article: Determining Exact RANS Operators with the Macroscopic Forcing Method (Final Report)
Determining Exact RANS Operators with the Macroscopic Forcing Method (Final Report) Open
View article: Direct numerical simulations of three-component Rayleigh–Taylor mixing and an improved model for multicomponent reacting mixtures
Direct numerical simulations of three-component Rayleigh–Taylor mixing and an improved model for multicomponent reacting mixtures Open
We present direct numerical simulations of a three-layer Rayleigh–Taylor instability (RTI) problem with a configuration based on the experiments of Suchandra & Ranjan ( J. Fluid Mech. , vol. 974, 2023, A35) and Jacobs & Dalziel ( J. Fluid …
View article: Interactions of laser-driven tin ejecta microjets over phase transition boundaries
Interactions of laser-driven tin ejecta microjets over phase transition boundaries Open
Ejecta microjets offer an experimental methodology to study high-speed particle laden-flow interactions, as microjets consist of millions of particulates traveling at velocities of several kilometers per second and are easily generated by …
View article: Non-locality of mean scalar transport in two-dimensional Rayleigh–Taylor instability using the macroscopic forcing method
Non-locality of mean scalar transport in two-dimensional Rayleigh–Taylor instability using the macroscopic forcing method Open
The importance of non-locality of mean scalar transport in two-dimensional Rayleigh–Taylor Instability (RTI) is investigated. The macroscopic forcing method is utilized to measure spatio-temporal moments of the eddy diffusivity kernel repr…
View article: Neural Optimizer Equation, Decay Function, and Learning Rate Schedule Joint Evolution
Neural Optimizer Equation, Decay Function, and Learning Rate Schedule Joint Evolution Open
A major contributor to the quality of a deep learning model is the selection of the optimizer. We propose a new dual-joint search space in the realm of neural optimizer search (NOS), along with an integrity check, to automate the process o…
View article: Evolving Loss Functions for Specific Image Augmentation Techniques
Evolving Loss Functions for Specific Image Augmentation Techniques Open
Previous work in Neural Loss Function Search (NLFS) has shown a lack of correlation between smaller surrogate functions and large convolutional neural networks with massive regularization. We expand upon this research by revealing another …
View article: Experiments and Simulations of Laser-Driven Tin Ejecta Microjets
Experiments and Simulations of Laser-Driven Tin Ejecta Microjets Open
View article: Nonplanar effects in simulations of laser-driven ejecta microjet experiments
Nonplanar effects in simulations of laser-driven ejecta microjet experiments Open
Recent experiments of laser-driven ejecta microjets performed at OMEGA 60 reveal tortuous jets whereby the jets appear to deviate from their initial trajectory as they travel in vacuum. To understand these data, we perform two dimensional …
View article: Neural Loss Function Evolution for Large-Scale Image Classifier Convolutional Neural Networks
Neural Loss Function Evolution for Large-Scale Image Classifier Convolutional Neural Networks Open
For classification, neural networks typically learn by minimizing cross-entropy, but are evaluated and compared using accuracy. This disparity suggests neural loss function search (NLFS), the search for a drop-in replacement loss function …
View article: RANSBox: A zero-dimensional modular software package for Reynolds-averaged Navier-Stokes modeling
RANSBox: A zero-dimensional modular software package for Reynolds-averaged Navier-Stokes modeling Open
View article: Two self-similar Reynolds-stress transport models with anisotropic eddy viscosity
Two self-similar Reynolds-stress transport models with anisotropic eddy viscosity Open
Two Reynolds-averaged Navier-Stokes models with full Reynolds-stress transport (RST) and tensor eddy viscosity are presented. These new models represent RST extensions of the k-2L-a-C and k-ϕ-L-a-C models by Morgan [Phys. Rev. E 103, 05310…
View article: Mass and momentum transport in the Tilted Rocket Rig experiment
Mass and momentum transport in the Tilted Rocket Rig experiment Open
Here, high-fidelity large eddy simulations of the inclined Rayleigh-Taylor instability in the Tilted Rocket Rig experimental configuration [Smeeton and Youngs, AWE Report No. O 35/87 (1987)] are performed using a tenth-order compact finite…
View article: Nonlocality of Mean Scalar Transport in Two-Dimensional Rayleigh-Taylor Instability Using the Macroscopic Forcing Method
Nonlocality of Mean Scalar Transport in Two-Dimensional Rayleigh-Taylor Instability Using the Macroscopic Forcing Method Open
The importance of nonlocality of mean scalar transport in 2D Rayleigh-Taylor Instability (RTI) is investigated. The Macroscopic Forcing Method (MFM) is utilized to measure spatio-temporal moments of the eddy diffusivity kernel representing…
View article: Screening for Quality of Life in a Neurology Tic Clinic Using Quality Improvement Methodology
Screening for Quality of Life in a Neurology Tic Clinic Using Quality Improvement Methodology Open
View article: Large-eddy simulation and Reynolds-averaged Navier-Stokes modeling of three Rayleigh-Taylor mixing configurations with gravity reversal
Large-eddy simulation and Reynolds-averaged Navier-Stokes modeling of three Rayleigh-Taylor mixing configurations with gravity reversal Open
High-fidelity large-eddy simulation (LES) is performed of Rayleigh-Taylor (RT) mixing in three different configurations involving gravity reversal. In each configuration, LES results are compared with one-dimensional Reynolds-averaged Navi…
View article: Simulation and Reynolds-averaged Navier-Stokes modeling of a three-component Rayleigh-Taylor mixing problem with thermonuclear burn
Simulation and Reynolds-averaged Navier-Stokes modeling of a three-component Rayleigh-Taylor mixing problem with thermonuclear burn Open
Rayleigh-Taylor mixing in the presence of a third component with intermediate density is investigated through three-dimensional large-eddy simulation (LES) with a high-order compact finite-difference code. Two configurations are considered…
View article: Experimental Observations of Laser-Driven Tin Ejecta Microjet Interactions
Experimental Observations of Laser-Driven Tin Ejecta Microjet Interactions Open
The study of high-velocity particle-laden flow interactions is of importance for the understanding of a wide range of natural phenomena, ranging from planetary formation to cloud interactions. Experimental observations of particle dynamics…
View article: Self-consistent, high-order spatial profiles in a model for two-fluid turbulent mixing
Self-consistent, high-order spatial profiles in a model for two-fluid turbulent mixing Open
A Reynolds-averaged Navier-Stokes model is presented with the property that it admits self-consistent, high-order spatial profiles in simulations of two-fluid turbulent mixing layers. Whereas previous models have been limited by the assump…
View article: Scalar mixing in a Kelvin-Helmholtz shear layer and implications for Reynolds-averaged Navier-Stokes modeling of mixing layers
Scalar mixing in a Kelvin-Helmholtz shear layer and implications for Reynolds-averaged Navier-Stokes modeling of mixing layers Open
Large-eddy simulation of a temporally evolving Kelvin-Helmholtz (KH) mixing layer is performed with the tenth-order compact difference code miranda to examine the steady-state behavior of a passive scalar in a shear-driven mixing layer. It…
View article: Simulation and flow physics of a shocked and reshocked high-energy-density mixing layer
Simulation and flow physics of a shocked and reshocked high-energy-density mixing layer Open
View article: Hydrodynamic computations of high-power laser drives generating metal ejecta jets from surface grooves
Hydrodynamic computations of high-power laser drives generating metal ejecta jets from surface grooves Open
Understanding dynamic fragmentation in shock-loaded metals and predicting properties of the resulting ejecta are of considerable importance for both basic and applied science. The nature of material ejection has been shown to change drasti…
View article: Development of high power laser platforms to study metal ejecta interactions
Development of high power laser platforms to study metal ejecta interactions Open
View article: Hydrodynamic and atomistic studies in support of high power laser experiments for metal ejecta recollection and interactions
Hydrodynamic and atomistic studies in support of high power laser experiments for metal ejecta recollection and interactions Open
Shock-driven material can emit a fine spray of ejecta from its free surface. Understanding the dynamic and interaction of the metal ejecta is important to areas of study as diverse as industrial safety, astrophysics, spacecraft shielding, …
View article: Video: Simulating Turbulent Fluid Mixing using LLNL's Sierra Supercomputer
Video: Simulating Turbulent Fluid Mixing using LLNL's Sierra Supercomputer Open
View article: Parametric investigation of the transition to turbulence in Rayleigh–Taylor mixing
Parametric investigation of the transition to turbulence in Rayleigh–Taylor mixing Open
View article: The sudden viscous dissipation of compressing turbulence for a two-component fluid
The sudden viscous dissipation of compressing turbulence for a two-component fluid Open