Direct simulation Monte Carlo (DSMC) of shock interaction in hypersonic low density flow is developed. Three collision molecular models, including hard sphere (HS), variable hard sphere (VHS), and variable soft sphere (VSS), are employed in the DSMC study. The simulations of double-cone and Edney's type IV hypersonic shock interactions in low density flow are performed. Comparisons between DSMC...

Hypersonic aerothermodynamics for a probe entering a planetary atmosphere is an important issue in space exploration. The probe experiences various Knudsen number regimes, ranging from rarefied to continuum, due to density variation in the planet’s atmosphere. To simulate such multiscale flows, a novel hybrid particle scheme is employed in the present work. The hybrid particle scheme employs th...

The direct simulation Monte Carlo (DSMC) method is one of the most popular numerical methods used to model rarefied gas environment flows. In order to predict the accuracy of a solution obtained by the DSMC method we have to be able to estimate its accuracy. In the work presented here we have developed a technique to estimate the numerical accuracy of the DSMC method. This paper presents a deri...

This study examines a new hybrid particle scheme used as an alternative means of multiscale flow simulation. The hybrid particle scheme employs the direct simulation Monte Carlo (DSMC) method in rarefied flow regions and the low diffusion (LD) particle method in continuum flow regions. The numerical procedures of the low diffusion particle method are implemented within an existing DSMC algorith...

A low diffusion particle method for simulating compressible low Knudsen number gas flows is modified for application to flows involving nonequilibrium distributions in rotational and vibrational energy modes. This method is closely based on the direct simulation Monte Carlo (DSMC) method, and has been developed for use in a strongly coupled hybrid scheme with DSMC. In simulations employing this...

Gas flows encountered in micro/nano scale devices are often low speed and non-continuum. The Direct Simulation Monte Carlo (DSMC), a popular molecular based simulation technique for rarefied gas, has proven to be inefficient in dealing with low-speed gas flows. In this paper, we present the Octant Flux Splitting Information Preserving DSMC (OSIP-DSMC) method as an efficient DSMC method for micr...

Vibrational relaxation is an important physical process in hypersonic flows. Activation of the vibrational mode affects the fundamental thermodynamic properties and finite rate relaxation can reduce the degree of dissociation of a gas. Low fidelity models of vibrational activation employ a relaxation time to capture the process at a macroscopic level. High fidelity, state-resolved models have b...

The direct simulation Monte Carlo method (DSMC) has evolved over 50 years into a powerful numerical technique for the computation of thermochemcial nonequilibrium gas flows. In this context, nonequilibrium means that velocity and internal energy distribution functions are not in equilibrium forms due to a low number of intermolecular collisions within a fluid element. In hypersonic flow, nonequ...

A multiscale method that couples direct simulation Monte Carlo (DSMC) method with Navier-Stokes equations is presented. The multiscale method is based on the Schwarz coupling of the DSMC and Navier-Stokes subdomains. Dirichlet boundary conditions are used at the coupling interfaces. The Navier-Stokes equations are solved using a scattered point based finite cloud method. Data interpolation betw...

The implementation of a modular particle-continuum (MPC) numerical method is presented which solves the Navier-Stokes (NS) equations in regions of near-equilibrium and uses the direct simulation Monte Carlo (DSMC) method where the flow is in non-equilibrium. A mesh refinement procedure is described which allows the NS equations to be solved on a relatively coarse mesh using large implicit time-...