A new Cartesian implementation of the direct simulation Monte Carlo (DSMC) method, named the hypersonic aerothermodynamics particle (HAP) code, is presented. This code is intended for rapid setup and simulation of rarefied flow problems, and as a framework for evaluating new physical models and numerical techniques. Unique features include the use of nonuniform Cartesian adaptive subcells, a co...

Airflow over a flat plate at zero incidence is investigated as a function of the Reynolds number Re and the Mach number M under subsonic, low-Reynolds-number conditions. The flows are simulated using the direct simulation Monte Carlo (DSMC) method and the information preservation (IP) method that is a modified DSMC method developed for low-speed rarefied gas flows. Good agreement is obtained be...

  Micro scale gas flows has attracted significant research interest in the last two decades. In this research, the fluid flow of gases in the stepped micro-channel at a wide range of Knudsen number has been analyzed with using the Lattice Boltzmann (MRT) method. In the model, a modified second-order slip boundary condition and a Bosanquet-type effective viscosity are used to consider the veloci...

Abstract. In this paper we present a fully deterministic method for the numerical solution to the Boltzmann equation of rarefied gas dynamics in a bounded domain for multi-scale problems. Periodic, specular reflection and diffusive boundary conditions are discussed and investigated numerically. The collision operator is treated by a Fourier approximation of the collision integral, which guarant...

Rarefied gas flows generated by resonating nanomechanical structures pose a significant challenge to theoretical analysis and physical interpretation. The inherent noncontinuum nature of such flows obviates the use of classical theories, such as the Navier-Stokes equations, requiring more sophisticated physical treatments for their characterization. In this Letter, we present a universal dynami...

Free-molecular pressure probes are employed to deduce particle flux in highly rarefied flow fields, such as the farfield or the backflow region of a plume expanding into vacuum. Analytical approaches to model the probe behavior are known in the literature for some time now. Numerical methods such as DSMC however allow to conduct investigations into the probe response in regimes inaccessible to ...

Cercignani’s conjecture assumes a linear inequality between the entropy and entropy production functionals for Boltzmann’s nonlinear integral operator in rarefied gas dynamics. Related to the field of logarithmic Sobolev inequalities and spectral gap inequalities, this issue has been at the core of the renewal of the mathematical theory of convergence to thermodynamical equilibrium for rarefied...

Viscous flow, effusion, and thermal transpiration are the main gas transport modalities for a rarefied gas in a macro-porous medium. They have been well quantified only in the case of simple geometries. This paper develops a model based on the homogenization of kinetic equations producing effective transport properties (permeability, Knudsen diffusivity, thermal transpiration ratio) in any poro...

Flow over micro-scale airfoils is investigated in order to understand the aerodynamic issues related to micro air vehicle design and performance. Studies have shown that such low Reynolds number flow exhibits rarefied phenomena and a flat plate having a thickness ratio of 5% has better aerodynamic performance than conventional streamlined airfoils. This paper simulates gas flows over a 5% flat ...

For increasingly rarefied flowfields, the predictions from continuum formulation, such as the Navier–Stokes equations lose accuracy. These inaccuracies are attributed primarily to the linear approximations of the stress and heat flux terms in the Navier– Stokes equations. The inclusion of higher order terms, such as Burnett, or high-order moment equations, could improve the predictive capabilit...