Aims. The break-up of a dustball meteoroid is investigated numerically based on fluid dynamics simulations the meteoroid’s atmospheric entry flow. Both thermal and mechanical mechanisms are implemented, in order to investigate disintegration. Methods. A three dimensional model composed thousands small spherical grains was used flow simulation, performed with direct simulation Monte Carlo (DSMC)...

Accurate evaluation of damping in laterally oscillating microstructures is challenging due to the complex flow behavior. In addition, device fabrication techniques and surface properties will have an important effect on the flow characteristics. Although kinetic approaches such as the direct simulation Monte Carlo (DSMC) method and directly solving the Boltzmann equation can address these chall...

The aim of this work is to simulate rare ed gas ow in complex geometries, under ow conditions that range from the hydrodynamic, through the transitional, to the molecular regimes. Existing computational models apply to molecular or viscous ow, but the treatment of the transitional ow is still underdeveloped. To deal with the di cult transitional ow, two models with overlapping ranges of applica...

The implementation of an adaptive mesh-embedding (h-re%nement) scheme using unstructured grid in two-dimensional direct simulation Monte Carlo (DSMC) method is reported. In this technique, local isotropic re:nement is used to introduce new mesh where the local cell Knudsen number is less than some preset value. This simple scheme, however, has several severe consequences a;ecting the performanc...

The advent of highly efficient and superior digital devices and fast microprocessors for control application has opened the field of discrete time controller design. This paper presents an exciting application of magnetic levitation system using discrete sliding mode control. There is a limited volume of literature available for discrete sliding mode control as applied to magnetic levitation sy...

A recently developed high-order velocity-slip boundary condition is validated for gas micro ows, by comparing predictions of the new model against the Ž rst-order slip condition and the direct-simulation Monte Carlo (DSMC) results. Numerical solutions of gas  ow through microchannels and backward-facing step geometry are presented. The backwardfacing step geometry is a suitable testbed for st...

We summarize our recent contributions to the development of macroscopic transport equations for rarefied gas flows. A combination of the ChapmanEnskog expansion and Grad’s moment method, termed as the order of magnitude method, yields the regularized 13 moment equations (R13 equations) which are of super-Burnett order. A complete set of boundary conditions is derived from the boundary condition...

An efficient and accurate parallel coupled DSMC–NS method using three-dimensional unstructured grid topology is proposed and verified for the simulation of high-speed gas flows involving continuum and rarefied regimes. A domain overlapping strategy, taking advantage of unstructured data format, with Dirichlet–Dirichlet type boundary conditions based on two breakdown parameters is used iterative...

combined residual modification with artificial neural network sign estimation to improve the prediction accuracy. Yao, et al [3] added an adaptive value in the grey differential equation to improve system performance. Su, Lin, and Hsu [4] proposed a Markov-Fourier grey model, in which Fourier series is used to fit residuals and Markov matrices is employed to encode possible global information g...