In the present study the Direct Simulation Monte Carlo (DSMC) method, which is one of most the widely used numerical methods to study the rarefied gas flows, is applied to investigate the flow characteristics of a hypersonic and subsonic flow over a backward-facing step. The work is driven by the interest in exploring the effects of the Mach number on the flow behaviour. The primary objective of this paper is to study the variation of velocity, pressure, and temperature with Mach number. The numerical tool is validated with well-established results from the literature and a good agreement is found among them. The flow is analyzed and some comments on the characteristics of the flow are also added.

In the present study the Direct Simulation Monte Carlo (DSMC) method, which is one of the widely used numerical method to study the rarefied gas flows, is applied to investigate the flow characteristics of a hypersonic and subsonic flow over a backward-facing step. The work is driven by the interest in exploring the effects of the Mach number on the rarefied flow behaviour. The primary objective of this paper is to study the variation of velocity, pressure and temperature with Mach number. The numerical tool is validated with well established results from the literature and a good agreement is found among them. The computational results indicate that the flow downstream of the step is effected by the strong expansion near the step. The compressiblity and rarefaction effects also influence the velocity and temperature distributions in the hydrodynamic and thermal boundary layers.

The present work investigates the effects of rarefaction on gas flow patterns in a lid-driven cavity using the simulation package dsmcFoam, on the OpenFOAM platform. Direct Simulation Monte Carlo (DSMC) method is a simulation technique which caters to the regime in between the computationally intensive molecular dynamics solvers, as well as the often inaccurate NS based solvers (applied to the rarefied gas simulations). It was proposed by G.A. Bird which employs the stochastic modelling of particle motion.Simulations are performed and results are verified for the flow of a rarefied gas (Argon) for different lid velocities within the domain. The results are presented as streamlines, contours of velocity, pressure and temperature,along with velocities in X and Y directions. They have been found to be in good agreement with the previous experimental and numerical observations. Our simulations show that these eddies are much harder to observe in the rarefied domain, and cannot be observed upto velocities as high as 200m/s in a cavity with aspect ratio 1.

This work deals with the simulation of a 2D turbulence in Taylor-Couette flows. We investigate if a laminar flow acts as a global attractor in 2D for large Reynolds number, or do other stable states exist. Since in case of channel flows, the laminar flow seems to be a global attractor, the question is if shear flows themselves show such behavior in curved geometries. While working, another interesting physical observation was made about the non-monotonic relaxation to the laminar flow: Starting from values significantly higher than laminar, the total kinetic energy decreases to a lesser value and then grows back to give the laminar flow. This phenomenon is studied in some detail and a possible reason for this is then examined. The work also investigatesthe creation and destruction of vortices inside the domain and draws observations based on the sign of the vortices relative to the vorticity of the laminar flow. Since the creation and subsequent death of turbulence is a very interesting observation and can only be seen in 2D, it is studied extensively.

The present study is to investigate the behavior of a monoatomic gas enclosed in a cavity with both the top and bottom walls imparting motion to the fluid. The problem is studied for single and double-sided lid-driven flow for various wall velocities as well as parallel and anti-parallel wall motions. These types of flow have many industrial applications such as drying and melt spinning. In contrast to the single-sided flows the vortex patterns obtained in the double-sided flows are different and hence it merits a thorough examination, which is studied in this paper using the Direct Simulation Monte Carlo (DSMC) method. The DSMC method proposed by G.A. Bird is based on the kinetic theory in which the molecular motion is modeled stochastically. The computational model has been implemented in OpenFOAM software using the solver named dsmcFoam. Various flow features have been examined such as eddies and vortices.