Direct simulation Monte Carlo (DSMC) is an essential tool in the modeling of spacecraft atmospheric entry. The accuracy transport processes DSMC simulations depends on collision cross section parameters used to model particle interactions. In this work, we provide a comprehensive collision-specific Variable Soft Sphere (VSS) parameter database for accurate properties DSMC. A Nelder–Mead optimization scheme find optimized VSS from integrals, which are acquired either high-fidelity literature...

A new set of continuum breakdown parameters, rigorously derived from Generalized Chapman-Enskog theory, to capture regions strong thermal and chemical nonequilibrium for high speed, chemically reacting flows is presented. Detailed analysis shows that reactions can indirectly contribute via diffusion fluxes.

A technique to compute vibrationally resolved transport collision integrals for atom-diatom systems directly from ab inito potential energy surfaces (PES) is presented. These calculations are performed the oxygen employing Varga et al. set of PES, and Guyta-Yos style fits data provided. It found that simple empirical models often unable capture dependence these on vibrational state molecule. Differences up 80% observed between model predictions values computed PES.

Enabled by a newly developed species perturbation parameter, an analysis identifies forebody surface chemistry, among all other competing thermophysical processes, as the key contributor to continuum breakdown in hypersonic reacting wake flows.

A methodology is outlined for computing state-resolved transport collision integrals from potential energy surfaces (PES). This method then applied to the O+O2 system compute vibrational state (StS) collisional quantities based on Varandas and Pais PES [1] recent ab initio developed by Varga et al. [2]. State-based potentials that describe interaction of an O atom with O2 molecule at a particular level extracted singlet 1 A′ surface al., are used StS scattering profiles. Using these results,...

Hypersonic reentry flows span a wide range of length scales where regions both rarefied and continuum flow exist. Traditional computational fluid dynamics (CFD) techniques do not provide an accurate solution for the such 'mixed' fields. Although direct simulation Monte Carlo (DSMC) can be used to accurately capture features fields, they are computationally expensive when employed simulate low Knudsen number regimes. Thus, hybrid framework seamlessly combining two methodologies, CFD DSMC,...

Mass diffusion in multicomponent gas mixtures is governed by a coupled system of linear equations for the diffusive mass fluxes terms thermodynamic driving forces, known as generalized Stefan–Maxwell equation. In computations mixtures, this coupling between different components results considerable computational overhead. Consequently, simplified models explicit functions forces are an attractive alternative. These can be interpreted approximate solution to Simplified require specification...

A state-to-state two-step binary collision (TSBC) recombination model is developed for the rovibrationally coupled database of cross-sections from quasi-classical trajectory (QCT) calculations. The current work contains two parts. In first part, framework has been extended to include a resolved our previous which can only apply vibrationally QCT database. this framework, product orbiting-pair (OP) lifetime and formation cross-section included in model, rather than quantifying these...

In the time since Navier–Stokes equations were introduced more than two centuries ago, their application to problems involving real gas effects has relied on appropriate closure for mass, momentum, and energy transport fluxes via constitutive laws. Determination of corresponding coefficients, most readily obtained through generalized Chapman–Enskog theory, requires knowledge intermolecular potentials rotationally vibrationally excited molecules. Recent advances in computational chemistry...