Parallel Particle Simulation of the Near-Continuum Hypersonic Flows Over Compression Ramps

2003 ◽  
Vol 125 (1) ◽  
pp. 181-188 ◽  
Author(s):  
J.-S. Wu ◽  
K.-C. Tseng
Keyword(s):  
Flow Field ◽  
Direct Simulation Monte Carlo ◽  
Adaptive Mesh ◽  
Mean Free Path ◽  
Particle Simulation ◽  
Computational Time ◽  
Local Mean ◽  
Simulation Monte Carlo ◽  
Compression Ramp ◽  
Compression Ramps

This paper describes the analysis of the near-continuum hypersonic flow over a compression ramp using the two-dimensional parallel direct simulation Monte Carlo (DSMC) method. Unstructured and triangular solution-based adaptive mesh depending on the local mean free path is used to improve the resolution of solution for the flow field with highly varying properties. In addition, a freestream parameter is defined to help reduced the cell numbers in the freestream area, resulting in appreciable decrease of the computational time (20–30%) without sacrificing the accuracy of the solution. The two-step multilevel graph partition technique is used for physical domain decomposition, employing estimated particle number distribution in each cell as the graph vertex weight. 32 IBM-SP2 processors are used throughout the study unless otherwise specified. The Effect of the outflow vacuum boundary condition, compression ramp angle, freestream condition, and length of the ramp to the flow field are investigated. Computational results are compared with previous numerical results whenever available.

Theoretical and DSMC Study on Heat Conduction of Gas in Nanoscale Pores

2016 ◽  
Author(s):  
Chuan-Yong Zhu ◽  
Zeng-Yao Li
Keyword(s):  
Heat Conduction ◽  
Numerical Study ◽  
Direct Simulation Monte Carlo ◽  
Mean Free Path ◽  
Local Heat ◽  
Temperature Jumps ◽  
Thermal Conductivity Model ◽  
Local Heat Flux ◽  
Side Walls ◽  
Simulation Monte Carlo

This article presents a theoretical and numerical study on the heat conduction of gas confined in a nanoscale cube. An effective thermal conductivity model of confined gas using a modified mean free path is proposed for the heat conduction in transition regime inside a closure. Excellent agreement of the present model with the results from our simulations by the method of direct simulation Monte Carlo (DSMC) has been achieved for different boundary conditions of side walls. The temperature jumps and the reduction of local heat flux near the side walls are observed from the DSMC results.

A Direct Simulation Monte Carlo Approach for the Analysis of Granular Damping

2006 ◽  
Vol 2 (2) ◽  
pp. 180-189 ◽  
Author(s):  
X. Fang ◽  
J. Tang
Keyword(s):  
Monte Carlo ◽  
Vibration Suppression ◽  
Direct Simulation Monte Carlo ◽  
Structural Vibration ◽  
Computational Time ◽  
Coupled Analysis ◽  
Granular System ◽  
Direct Simulation ◽  
Simulation Monte Carlo ◽  
Granular Damping

Granular damping, which possesses promising features for vibration suppression in harsh environments such as in turbo-machinery and spacecraft, has been studied using empirical analysis and more recently using the discrete element method (DEM). The mechanism of granular damping is nonlinear and, when numerical analyses are employed, usually a relatively long simulation time of structural vibration is needed to reflect the damping behavior. The present research explores the granular damping analysis by means of the direct simulation Monte Carlo (DSMC) approach. Unlike the DEM that tracks the motion of granules based upon the direct numerical integration of Newton’s equations, the DSMC is a statistical method derived from the Boltzmann equation to describe the velocity evolution of the granular system. Since the exact time and locations of contacts among granules are not calculated in the DSMC, a significant reduction in computational time/cost can be achieved. While the DSMC has been exercised in a variety of gas/granular systems, its implementation to granular damping analysis poses unique challenges. In this research, we develop a new method that enables the coupled analysis of the stochastic granular motion and the structural vibration. The complicated energy transfer and dissipation due to the collisions between the granules and the host structure and among the granules is directly analyzed, which is essential to damping evaluation. Also, the effects of granular packing ratio and the excluded volume of granules, which may not be considered in the conventional DSMC approach, are explicitly incorporated in the analysis. A series of numerical studies are performed to highlight the accuracy and efficiency of the new approach.

scholarly journals Adaptive Mesh and Algorithm Refinement Using Direct Simulation Monte Carlo

1999 ◽  
Vol 154 (1) ◽  
pp. 134-155 ◽  
Author(s):  
Alejandro L Garcia ◽  
John B Bell ◽  
William Y Crutchfield ◽  
Berni J Alder
Keyword(s):  
Monte Carlo ◽  
Direct Simulation Monte Carlo ◽  
Adaptive Mesh ◽  
Direct Simulation ◽  
Simulation Monte Carlo

Granular Damping Analysis Using a Direct Simulation Monte Carlo Approach

2006 ◽  
Author(s):  
X. Fang ◽  
J. Tang
Keyword(s):  
Monte Carlo ◽  
Direct Simulation Monte Carlo ◽  
System Optimization ◽  
Numerical Analyses ◽  
Structural Vibration ◽  
Computational Time ◽  
Granular System ◽  
Direct Simulation ◽  
Simulation Monte Carlo ◽  
Granular Damping

Granular damping, which possesses promising features for vibration suppression in harsh environment, has been studied using empirical analysis and more recently using the discrete element method (DEM). The mechanism of granular damping is highly nonlinear, and, when numerical analyses are performed, usually a relatively long simulation time of structural vibration is needed to reflect the damping behavior especially at low frequency range. The present research explores the granular damping analysis by means of the Direct Simulation Monte Carlo (DSMC) approach. Unlike the DEM that tracks the motion of granules using the direct numerical integration of Newton's equations, the DSMC is a statistical approach derived from the Boltzmann equation to describe the velocity evolution of the granular system. Since the exact time and locations of contacts among granules are not calculated in the DSMC, a significant reduction in computational time/cost can be achieved. While the DSMC has been exercised in a variety of granular systems, its implementation to granular damping analysis poses unique challenges. In this research, we develop a new method that enables the coupled analysis of the stochastic granular motion and the structural vibration. The complicated energy transfer and dissipation due to the collisions between the granules and the host structure and among the granules is directly and accurately incorporated into the analysis, which is essential to damping evaluation. Also, the effects of granular packing ratio and the excluded volume of granules, which may not be included in conventional DSMC method, are explicitly taken into account in the proposed approach. A series of numerical analyses are performed to highlight the accuracy and efficiency of the new approach. Using this new algorithm, we can carry out parametric analysis on granular damping to obtain guidelines for system optimization.

A new direct simulation Monte Carlo implementation for more efficient simulation of hypersonic flow over arbitrarily shaped bodies using dynamic cells

2016 ◽  
Vol 231 (1) ◽  
pp. 82-97
Author(s):  
RV Reji ◽  
S Anil Lal
Keyword(s):  
Monte Carlo ◽  
High Speed ◽  
Direct Simulation Monte Carlo ◽  
Computational Time ◽  
Optimum Number ◽  
Gas Flows ◽  
Direct Simulation ◽  
Simulation Monte Carlo ◽  
Boundary Curves ◽  
Number Of Particles

Methods are reported for less computationally expensive and more accurate implementations of the direct simulation Monte Carlo (DSMC) method for the simulation of high speed gas flows over arbitrarily shaped bodies. A new particle-tracking algorithm with a saving of computational time of up to 10% is reported in which tracking of particles is done with the help of big triangles having vertices lying on the boundary curves. An algorithm has been developed to generate DSMC cells for collision and sampling that contain a prescribed number of molecules. This algorithm is able to generate over 90% cells having the optimum number of seven or eight molecules for simulating collisions. Sampling for macroscopic properties is done on dynamic cells that contain a number of particles varying spatially as a function of the local number density. A criterion for finding the number of particles in sampling cells is presented. This criterion has been found to result in accurate and fast simulation of two-dimensional hypersonic flows of argon over a wedge, and argon and nitrogen over a circular cylinder.

Numerical Methods for the Kinetic Theory of Fluids

2018 ◽  
Author(s):  
Sauro Succi
Keyword(s):  
Molecular Dynamics ◽  
Monte Carlo ◽  
Numerical Methods ◽  
Kinetic Theory ◽  
Computational Efficiency ◽  
Lattice Boltzmann ◽  
Direct Simulation Monte Carlo ◽  
Particle Methods ◽  
Direct Simulation ◽  
Simulation Monte Carlo

This chapter provides a bird’s eye view of the main numerical particle methods used in the kinetic theory of fluids, the main purpose being of locating Lattice Boltzmann in the broader context of computational kinetic theory. The leading numerical methods for dense and rarified fluids are Molecular Dynamics (MD) and Direct Simulation Monte Carlo (DSMC), respectively. These methods date of the mid 50s and 60s, respectively, and, ever since, they have undergone a series of impressive developments and refinements which have turned them in major tools of investigation, discovery and design. However, they are both very demanding on computational grounds, which motivates a ceaseless demand for new and improved variants aimed at enhancing their computational efficiency without losing physical fidelity and vice versa, enhance their physical fidelity without compromising computational viability.

Investigation of the Squeeze Film Dynamics Underneath a Microstructure With Large Oscillation Amplitudes and Inertia Effects

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Nadim A. Diab ◽  
Issam A. Lakkis
Keyword(s):  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Squeeze Film ◽  
Dsmc Method ◽  
Inertia Effects ◽  
Flow Parameters ◽  
Fluid Behavior ◽  
Dimensionless Groups ◽  
Simulation Monte Carlo ◽  
The Impact

This paper presents direct simulation Monte Carlo (DSMC) numerical investigation of the dynamic behavior of a gas film in a microbeam. The microbeam undergoes large amplitude harmonic motion between its equilibrium position and the fixed substrate underneath. Unlike previous work in literature, the beam undergoes large displacements throughout the film gap thickness and the behavior of the gas film along with its impact on the moving microstructure (force exerted by gas on the beam's front and back faces) is discussed. Since the gas film thickness is of the order of few microns (i.e., 0.01 < Kn < 1), the rarefied gas exists in the noncontinuum regime and, as such, the DSMC method is used to simulate the fluid behavior. The impact of the squeeze film on the beam is investigated over a range of frequencies and velocity amplitudes, corresponding to ranges of dimensionless flow parameters such as the Reynolds, Strouhal, and Mach numbers on the gas film behavior. Moreover, the behavior of compressibility pressure waves as a function of these dimensionless groups is discussed for different simulation case studies.

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