Aerothermodynamic modelling of meteor entry flows

2019 ◽  
Vol 492 (2) ◽  
pp. 2308-2325 ◽  
Author(s):  
Federico Bariselli ◽  
Aldo Frezzotti ◽  
Annick Hubin ◽  
Thierry E Magin
Keyword(s):  
Cross Sections ◽  
Impact Ionization ◽  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Vapour Phase ◽  
Molecular Flow ◽  
Material Transport ◽  
Dsmc Method ◽  
Detailed Chemistry ◽  
Ionization Coefficients

ABSTRACT Due to their small size and tremendous speeds, meteoroids often burn up at high altitudes above 80 km, where the atmosphere is rarefied. Ground radio stations allow us to detect the concentration of electrons in the meteoroid trail, which are produced by hyperthermal collisions of ablated species with the freestream. The interpretation of these data currently relies on phenomenological methods, derived under the assumption of free molecular flow, that poorly accounts for the detailed chemistry, diffusion in the vapour phase, and rarefied gas effects. In this work, we employ the direct simulation Monte Carlo (DSMC) method to analyse the detailed flowfield structure in the surroundings of a 1 mm meteoroid at different conditions, spanning a broad spectrum of Knudsen and Mach numbers, and we extract resulting ionization efficiencies. For this purpose, we couple the DSMC method with a kinetic boundary condition which models evaporation and condensation processes in a silicate material. Transport properties of the ablated vapour are computed following the Chapman–Enskog theory starting from Lennard–Jones potentials. Semi-empirical inelastic cross-sections for heavy- and electron-impact ionization of metals are computed analytically to obtain steric factors. The ionization of sodium is dominant in the production of free electrons, and hyperthermal air–vapour collisions play the most important role in this process. The ionization of air, classically disregarded, contributes to the electron production as significantly as ionization of magnesium and iron. Finally, we propose that DSMC could be employed as a numerical experiment providing ionization coefficients to be used in synthetic models.

Comparison of DSMC and CFD Models of Heat Transfer in a Rarefied Two-Dimensional Geometry

2018 ◽  
Author(s):  
Dilesh Maharjan ◽  
Mustafa Hadj-Nacer ◽  
Miles Greiner ◽  
Stefan K. Stefanov
Keyword(s):  
Heat Transfer ◽  
Rarefied Gas ◽  
Complex Geometry ◽  
Direct Simulation Monte Carlo ◽  
Accurate Method ◽  
Vacuum Drying ◽  
Helium Pressure ◽  
Two Dimensional ◽  
Dsmc Method ◽  
Cfd Simulations

During vacuum drying of used nuclear fuel (UNF) canisters, helium pressure is reduced to as low as 67 Pa to promote evaporation and removal of remaining water after draining process. At such low pressure, and considering the dimensions of the system, helium is mildly rarefied, which induces a thermal-resistance temperature-jump at gas–solid interfaces that contributes to the increase of cladding temperature. It is important to maintain the temperature of the cladding below roughly 400 °C to avoid radial hydride formation, which may cause cladding embrittlement during transportation and long-term storage. Direct Simulation Monte Carlo (DSMC) method is an accurate method to predict heat transfer and temperature under rarefied condition. However, it is not convenient for complex geometry like a UNF canister. Computational Fluid Dynamics (CFD) simulations are more convenient to apply but their accuracy for rarefied condition are not well established. This work seeks to validate the use of CFD simulations to model heat transfer through rarefied gas in simple two-dimensional geometry by comparing the results to the more accurate DSMC method. The geometry consists of a circular fuel rod centered inside a square cross-section enclosure filled with rarefied helium. The validated CFD model will be used later to accurately estimate the temperature of an UNF canister subjected to vacuum drying condition.

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.

scholarly journals Development of an Efficient Particle Approach for Micro-Scale Gas Flow Simulations

2009 ◽  
Author(s):  
Quanhua Sun ◽  
Feng Li ◽  
Jing Fan ◽  
Chunpei Cai
Keyword(s):  
Cell Size ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Gas Flows ◽  
Dsmc Method ◽  
Low Speed ◽  
Micro Scale ◽  
Information Preservation ◽  
Cfd Method

The micro-scale gas flows are usually low-speed flows and exhibit rarefied gas effects. It is challenging to simulate these flows because traditional CFD method is unable to capture the rarefied gas effects and the direct simulation Monte Carlo (DSMC) method is very inefficient for low-speed flows. In this study we combine two techniques to improve the efficiency of the DSMC method. The information preservation technique is used to reduce the statistical noise and the cell-size relaxed technique is employed to increase the effective cell size. The new cell-size relaxed IP method is found capable of simulating micro-scale gas flows as shown by the 2D lid-driven cavity flows.

scholarly journals Using Plücker Coordinates for Pumping Speed Evaluation of Molecular Pump in the DSMC Method

2001 ◽  
Vol 7 (1) ◽  
pp. 11-20 ◽  
Author(s):  
Fong-Zhi Chen ◽  
Ming-June Tsai ◽  
Yu-Wen Chang ◽  
Rong-Yuan Jou ◽  
Hong-Ping Cheng
Keyword(s):  
Three Dimensional ◽  
Direct Simulation Monte Carlo ◽  
Flow Simulation ◽  
Vacuum Pump ◽  
Ruled Surface ◽  
Molecular Flow ◽  
Dsmc Method ◽  
Plücker Coordinates ◽  
Straight Line ◽  
Speed Performance

In this study, the Plücker coordinates representation is used to formulate the ruled surface and the molecular path for pumping speed performance evaluation of a molecular vacuum pump. The ruled surface represented by the Pliicker coordinates is used to develop a criterion for when gas molecules hit the pump surface wall. The criterion is applied to analyze the flow rate of a new developed vacuum pump in transition regimes by using the DSMC (Direct Simulation Monte Carlo) method. When a molecule flies in a neutral electrical field its path is a straight line. If the molecular path and the generators of a ruled surface are both represented by the Pliicker coordinates, the position of the molecular hit on the wall can be verified by the reciprocal condition of the lines. The Plücker coordinates representation is quite convenient in the DSMC method for this three-dimensional molecular flow simulation.

scholarly journals Simulation of Rarefied Gas Flow in a Rectangular Enclosure

2019 ◽  
Author(s):  
Sumit Chamling Rai ◽  
Jayesh Sanwal ◽  
K Ram Chandra Murthy
Keyword(s):  
Gas Flow ◽  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Stochastic Modelling ◽  
Dsmc Method ◽  
Driven Cavity ◽  
Simulation Monte Carlo ◽  
Computationally Intensive ◽  
Velocity Pressure ◽  
Good Agreement

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.

DSMC Simulations of Squeeze Film Between a Micro Beam Undergoing Large Amplitude Oscillations and a Substrate

2012 ◽  
Author(s):  
Nadim A. Diab ◽  
Issam A. Lakkis
Keyword(s):  
Rarefied Gas ◽  
Numerical Study ◽  
Direct Simulation Monte Carlo ◽  
Squeeze Film ◽  
Rf Switch ◽  
Dsmc Method ◽  
Flow Parameters ◽  
Fluid Behavior ◽  
Simulation Monte Carlo ◽  
The Impact

This paper investigates the behavior of a gas film in a micro RF switch. A Two-dimensional numerical study of the flow field is performed as the micro-beam oscillates harmonically 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 RF switch (force exerted by gas on the beam’s front and back faces) are 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 non-continuum regime and, as such, the Direct Simulation Monte Carlo (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, velocity amplitudes, and for different film gases, corresponding to ranges of dimensionless flow parameters such as the Reynolds (Re), Strouhal (St) and Mach (Ma) numbers on the gas film behavior.

Statistical Modeling of Rarefied Gas Channel Flows

2009 ◽  
Author(s):  
Seckin Gokaltun ◽  
Michael C. Sukop ◽  
George S. Dulikravich
Keyword(s):  
Lattice Boltzmann ◽  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Direct Simulation ◽  
Channel Axis ◽  
Dsmc Method ◽  
Gas Channel ◽  
Simulation Monte Carlo ◽  
Boltzmann Method ◽  
Linear Pressure Distribution

Lattice Boltzmann method (LBM) and direct simulation Monte Carlo (DSMC) method are used for analysis of moderate Knudsen number phenomena. Simulation results are presented for pressure-driven isothermal rarefied channel flow at various pressure ratios. Analytical equations for non-linear pressure distribution and velocity profiles along the channel axis are used to verify the present LBM and DSMC results. We conclude that the LBM method can be used as an alternative model to DSMC simulations.

scholarly journals On the simulation of gas ionization by fast electrons

2021 ◽  
pp. 1-12
Author(s):  
Andrei Vsevolodovich Berezin ◽  
Aleksandr Duhanin Aleksandr Duhanin ◽  
Oleg Sergeevich Kosarev ◽  
Mikhail Borisovich Markov ◽  
Sergey Vladimirovich Parot'kin ◽  
...  
Keyword(s):  
Kinetic Equation ◽  
Cross Sections ◽  
Impact Ionization ◽  
Rarefied Gas ◽  
Initial Distribution ◽  
Secondary Electrons ◽  
Spatial Homogeneity ◽  
Fast Electrons ◽  
Gas Dynamic ◽  
Gas Ionization

The gas-dynamic parameters of an ionized medium formed during impact ionization of a rarefied gas by fast electrons are considered. The concentration, drift velocity, and specific energy of low-energy secondary electrons are constructed by an approximate solution of the kinetic equation. Approximations of the spatial homogeneity of the kinetic equation and the isotropy of the initial distribution of secondary electrons during impact ionization are used. Additional approximations are related to the structure of the distribution function of secondary electrons and averaging of the cross sections.

scholarly journals DSMC Simulation of Rarefied Gas Flow in a Single-sided and Double-sided Lid-Driven Cavity

2019 ◽  
Author(s):  
Jayesh Sanwal ◽  
Deepak Nabapure ◽  
Sreeram Rajesh ◽  
K Ram Chandra Murthy
Keyword(s):  
Melt Spinning ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Industrial Applications ◽  
Dsmc Method ◽  
Driven Cavity ◽  
Flow Features ◽  
Dsmc Simulation ◽  
Vortex Patterns

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.

scholarly journals Pumping Speed Measurement and Analysis for the Turbo Booster Pump

2004 ◽  
Vol 10 (1) ◽  
pp. 1-13 ◽  
Author(s):  
R. Y. Jou ◽  
S. C. Tzeng ◽  
J. H. Liou
Keyword(s):  
Rarefied Gas ◽  
High Vacuum ◽  
Direct Simulation Monte Carlo ◽  
Transitional Flow ◽  
Transition Flow ◽  
Dsmc Method ◽  
Dsmc Simulation ◽  
Computational Fluid Dynamics Cfd ◽  
Booster Pump ◽  
Cfd Method

This study applies testing apparatus and a computational approach to examine a newly designed spiral-grooved turbo booster pump (TBP), which has both volume type and momentum transfer type vacuum pump functions, and is capable of operating at optimum discharge under pressures from approximately 1000 Pa to a high vacuum. Transitional flow pumping speed is increased by a well-designed connecting element. Pumping performance is predicted and examined via two computational approaches, namely the computational fluid dynamics (CFD) method and the direct simulation Monte Carlo (DSMC) method. In CFD analysis, comparisons of measured and calculated inlet pressure in the slip and continuum flow demonstrate the accuracy of the calculation. Meanwhile, in transition flow, the continuum model of CFD is unsuitable for calculating such rarefied gas. The pumping characteristics for a full 3D model on a rotating frame in transition and molecular regimes thus are simulated using the DSMC method and then confirmed experimentally. However, when the Knudsen number is in the range 0.5 < Kn < 0.1, neither CFD computation nor DSMC simulation is suitable for analyzing the pumping speed of the turbo booster pump. In this situation, the experimental approach is the most appropriate and effective method for analyzing pumping speed. Moreover, the developed pump is tested using assessment systems constructed according to ISO and JVIS-005 standards, respectively. Comparisons are also made with other turbo pumps. The compared results show that the turbo booster pump presented here has good foreline performance.

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