James B. Scoggins

National Aeronautics and Space Administration · LaRC Aerothermodynamics Branch

The entry phase constitutes a design driver for aerospace systems that include such a critical step. This phase is characterized by hypersonic flows encompassing multiscale phenomena that require advanced modeling capabilities. However, because high-fidelity simulations are often computationally prohibitive, simplified models are needed in multidis...

The entry phase constitutes a design driver for aerospace systems that include such a critical step. This phase is characterized by hypersonic flows encompassing multiscale phenomena that require advanced modeling capabilities. However, since high fidelity simulations are often computationally prohibitive, simplified models are needed in multidisci...

Accurate transport properties of non-ionized gas mixtures of C, H, O, N, and Si-containing species at temperatures up to 4000 K are essential in many scientific fields. Mixture transport properties are computed through the solution of linear transport systems, requiring collision integrals as functions of temperature for each binary collision pair...

View Video Presentation: https://doi.org/10.2514/6.2021-2849.vid The effect of finite-rate internal energy transfer on shock interaction mechanisms of CO2-dominated flows is investigated. The polyatomic molecule has a relatively low characteristic vibrational temperature that causes vibrational degrees of freedom to be excited across a shock wave a...

The present study aims at providing insights into shock wave interference patterns in gas flows when a mixture different than air is considered. High-energy non-equilibrium flows of air and $$\hbox {CO}_2$$ CO 2 – $$\hbox {N}_2$$ N 2 over a double-wedge geometry are studied numerically. The impact of freestream temperature on the non-equilibrium sh...

We present a novel machine learning moment method for the closure of the moment transport equations associated with the solution of the Williams-Boltzmann equation for polydisperse, evaporating sprays. The method utilizes neural networks to learn optimal closures approximating the dynamics of the kinetic equation using a supervised learning approac...

Departures from thermal equilibrium in gases, when different temperatures characterize a mixture, arise in a wide range of industrial and academic applications. Therefore, the robust computation of linearly constrained, chemical equilibrium compositions for such mixtures in thermal non-equilibrium is an important topic for which numerous formulatio...

The Mutation++ library provides accurate and efficient computation of physicochemical properties associated with partially ionized gases in various degrees of thermal nonequilibrium. With v1.0.0, users can compute thermodynamic and transport properties, multiphase linearly-constrained equilibria, chemical production rates, energy transfer rates, an...

Context. Composition, mass, and trajectory parameters of meteors can be derived by combining observations with the meteor physics equations. The fidelity of these equations, which rely on heuristic coefficients, significantly affects the accuracy of the properties inferred. Aims. Our objective is to present a methodology that can be used to comput...

The Mutation++ library provides accurate and efficient computation of physicochemical properties associated with partially ionized gases in various degrees of thermal nonequilibrium. With v1.0.0, users can compute thermodynamic and transport properties, multiphase linearly-constrained equilibria, chemical production rates, energy transfer rates, an...

Aims. We present a fluid model that has been developed for multicomponent two-temperature magnetized plasmas in chemical non-equilibrium for the partially to fully ionized collisional regimes. We focus on transport phenomena with the aim of representing the atmosphere of the Sun. Methods. This study is based on an asymptotic fluid model for multico...

The development of a new generation of ablative thermal protection systems based on carbon-phenolic composite materials demands the accurate determination of transport properties of pyrolysis gases mixed in various atmospheres. The present work provides recommended collision data for the calculation of the transport properties for Mars and Earth re...

A first principles formulation for the calorically imperfect behavior of gases is here proposed within a Boltzmann-type discretisation of the Navier–Stokes equations. The formulation is intended to enhance the consistency of gas kinetic schemes (GKS) with the physics of supersonic and hypersonic regimes where vibrational and electronic energy modes...

Aims. A fluid model is developed for multicomponent two-temperature magnetized plasmas in chemical non-equilibrium from the partially-to fully-ionized collisional regimes. We focus on transport phenomena aiming at representing the chromosphere of the Sun. Methods. Graille et al. [M3AS 19(04):527-599, 2009] have derived an asymptotic fluid model for...

A fluid model is developed for multicomponent two-temperature magnetized plasmas in chemical non-equilibrium from the partially- to fully-ionized collisional regimes. We focus on transport phenomena aiming at representing the chromosphere of the Sun. Graille et al. [M3AS 19(04):527-599, 2009] have derived an asymptotic fluid model for multicomponen...

Meteor entry are characterized by complex shock layer physics such as radiation, evaporation of the meteoroid surface and the resulting chemistry process with the air constituents. In this work we present the analysis of a meteor entry using Computational Fluid Dynamic tools where a boundary condition for evaporation is implemented. Moreover the ra...

Cette thèse est centrée sur le couplage entre les phénomènes d’écoulement, d’ablation et de rayonnement au voisinage du point d’arrêt de véhicules d’entrée atmosphérique pourvus d’un système de protection thermique de type carbonephénolique. La recherche est divisée en trois parties : 1) le développement de méthodes numériques et d’outils pour la s...

Accurate thermodynamic properties for species found in carbon-phenolic gas mixtures are essential in predicting material response and heating of carbon-phenolic heat shields of planetary entry vehicles. A review of available thermodynamic data for species found in mixtures of carbon-phenolic pyrolysis and ablation gases and atmospheres rich with C,...

Many engineering applications involve reacting porous materials submitted to high temperatures. This work presents a detailed but pragmatic heat and mass transfer model for porous materials containing several solid phases and a single gas phase. The detailed chemical interactions occurring between the solid phases and the gas phase are modeled at t...

We propose a unified fluid model for multicomponent plasmas in thermal nonequilibrium accounting for the influence of the electromagnetic field. In a previous work, this model was derived from kinetic theory based on a generalized Chapman-Enskog perturbative solution of the Boltzmann equation, scaled using the ratio of electron to heavy-particle ma...

In this study, a Hybrid Statistical Narrow Band (HSNB) model is implemented to make fast and accurate predictions of radiative transfer effects on hypersonic entry flows. The HSNB model combines a Statistical Narrow Band (SNB) model for optically thick molecular systems, a box model for optically thin molecular systems and continua, and a Line-By-L...

The stable computation of linearly constrained, multiphase, chemical equilibrium compositions is an important topic for a wide range of industrial and academic applications. Numerous computational methods have been developed to solve such problems which are, in general, susceptible to failure under certain conditions due to numerical stiffness. In...

Ablative materials are used in thermal protection systems for atmospheric re-entry vehicle heat shields. A detailed chemical equilibrium heat and mass transport model for porous ablators is presented for the first time. The governing equations are volume-averaged forms of the conservation equations for gas density, gas elements, solid mass, gas mom...

A model for coupled flow, radiation, and ablation calculations along the stagnation lines of atmospheric entry vehicles is developed to study the effects these coupled phenomena have on each other as well as the predicted quantities of interest to vehicle designers. The flow model is based on the two-temperature, multicomponent, reacting Navier-Sto...

An adaptive spectral meshing algorithm is developed for atomic spectra when coupled with the hybrid statistical narrow band method developed at EM2C. The accuracy and CPU cost of the method is compared to full LBL calculations for FIRE II flight conditions. It is shown that the adaptive HSNB algorithm can provide good estimates of the stagnation li...

The development of the Mutation++ library is described which has been designed to compute thermodynamic and transport properties of ionized gases including equilibrium compositions and species production rates due to finite-rate elementary reactions. Thermodynamic properties are obtained from three separate databases: the NASA 7- and 9-coefficient...

Air plasma radiation in Local Thermodynamic Equilibrium (LTE) within cylindrical geometries is studied with an aim towards modeling the radiative transfer inside arc-constrictors, a central component of constricted-arc arc jets. A detailed database of spectral absorption coefficients for LTE air is computed using the NEQAIR code developed at NASA A...

A Nonequilibrium Ablation and Pyrolysis model is presented along with the development of a detailed kinetic mechanism for the decomposition of pyrolysis products for carbon-phenolic thermal protection systems. The detailed mechanism consists of 49 species and 136 reactions. A simple procedure for kinetic mechanism reduction is outlined and then use...

This work describes the development of a Thermal Protection System response model to study the affects of thermal and chemical nonequilibrium in the char layer. A new approach is developed where the pyrolysis gases are determined from a detailed chemical kinetic model and where the gas temperature is different from the char temperature. The resulti...