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Gore, Robert Allen

Publications and source records attributed to Gore, Robert Allen.

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

The tracer-BHR4 model for subgrid mixing layers

A model for the passive evolution of turbulent subgrid-scale mixing layers is developed based on the model of tracer-BHR model of Braun & Gore. The new model, tracer-BHR4, mainly differs from the previous iteration in that it aims to replicate the behavior of BHR4, instead of BHR3.1. The coefficients from BHR4 are used and a new model for mixing layer growth is developed to allow the tracer model to reproduce the de-mixing behavior seen in BHR4. Additionally, an improved timestep size controller is introduced. The new model is tested on problems containing Rayleigh-Taylor or Richtmyer-Meshkov mixing layers, and is able to reproduce the behavior of well resolved BHR4 simulations with reasonable accuracy.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2021

A multispecies turbulence model for the mixing and de-mixing of miscible fluids

A de-mix capable model for turbulence in compressible, variable density flows is proposed. The model is based on the Besnard-Harlow-Rauenzahn (BHR) family of models (Besnard D, Harlow F, Rauenzahn R, et al. Turbulence transport equations for variable-density turbulence and their relationship to two-field models. NM (United States): Los Alamos National Laboratory; 1992 (Technical Report LA-12303-MS), but is extended to track the evolution of the turbulent fluxes and fluctuations in the material mass fractions for each species present. The new evolution equations are introduced without requiring additional closures or new empirically tuned coefficients relative to previous BHR models, and are shown to improve the model’s ability to reproduce the behaviour of simulations containing mixing layers that are constrained by a stabilising force. As a result, the model is tested in a range of canonical flows including Rayleigh-Taylor driven, shock driven, and shear driven turbulence, and is shown to produce reasonable agreement with simulations and experiments in these scenarios.

42 ENGINEERING↗
DOE OSTI2021

Experimental validation of shock propagation through a foam with engineered macro-pores

The engineered macro-pore foam provides a new way to study thermonuclear burn physics by utilizing capsules containing deuterated (D) foam and filling tritium (T) gas in the engineered macro-pores. The implosion of a thermonuclear capsule filled with an engineered macro-pore foam will be complex due to the interaction of a shock wave with the engineered macro-pores. It is our goal to quantify how substantially complex foam structures affect the shape of shock and bulk shock speed. A cylinder-shape shock tube experiment has been designed and performed at the Omega Laser Facility. In order to examine how a foam structure will affect shock propagation, we performed several tests varying (1) engineered macro-pore size, (2) average foam density, and (3) with/without neopentane (C 5 H 12 ) gas. X-ray radiographic data indicate that shock speed through engineered macro-pore foams depends strongly on average foam density and less on pore size. In this work, experimental shock propagation data helped guide two numerical simulation approaches: (1) a 2D simulation with homogenizing foams rather than explicitly simulating engineered macro-pores and (2) a 2D toroidal-pore approximation adopting a toroidal-tube geometry to model engineered macro-pores.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

A passive model for the evolution of subgrid-scale instabilities in turbulent flow regimes

In this work, a zero-dimensional model for the development of turbulent mixing layers driven by Rayleigh–Taylor (RT) or Richtmyer–Meshkov (RM) instabilities is presented, for application in Reynolds-Averaged Navier–Stokes (RANS) simulations. The model approximates the behavior of the turbulent mixing layer at a passively advected tracer particle that sits on the material interface of interest in the simulation, and is used to provide initial conditions for the RANS model once the mixing layer width has developed to a size that may be resolved on the computational mesh. The model relies on approximations to the Besnard–Harlow–Rauenzahn (BHR) RANS closure equations and is thus consistent the turbulent development of the mixing layer, unlike previous models of this type which have focused on the early-time laminar development of RT or RM instabilities. These instabilities will often grow through an initially laminar state before developing into turbulence, and criteria for switching from an existing laminar model to the proposed turbulent model are considered. The proposed model reproduces the mixing layer development of RT and RM instabilities seen in mixed width resolving BHR RANS simulations to a reasonable degree of accuracy, and relaxes the need for the RANS simulation to resolve the mixed width as soon as the mixing layer becomes turbulent, which may be impractical in cases where the mixing layer grows through a wide range of scales.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗