For precise application of Bhatnagar–Gross–Krook (BGK) methods, assessing its accuracy in non-equilibrium flows is necessary. Generally, this assessment relies on macroscopic parameters, which are moments the velocity distribution function (VDF). However, flows, significance each moment diminishes as VDF deviates from Maxwellian VDF. This study investigates flows. Two Prandtl-corrected BGK ellipsoidal statistical and Shakhov (SBGK), compared with direct simulation Monte Carlo method. To...

The direct simulation Monte Carlo (DSMC) method is applicable over a wide range of Knudsen numbers. However, the binary collision events make DSMC prohibitively expensive near continuum regime. To address computational cost issue in high-density regions, particle-based Fokker–Planck (FP) has been studied. In FP method, particles evolve along independent stochastic paths, so required cell size and time step do not need to resolve collisional scale. While several monatomic diatomic models have...

Bhatnagar–Gross–Krook (BGK) models are widely used to study rarefied gas dynamics. However, as simplified versions of the Boltzmann collision model, their performances uncertain and need be carefully investigated in highly nonequilibrium flows. In this study, several common BGK models, such ellipsoidal statistical (ES-BGK) Shakhov (S-BGK) theoretically analyzed using moment equations. Then, numerical comparisons performed between model based on various benchmarks, Fourier flow, Couette shock...

The direct simulation Monte Carlo (DSMC) method has become a powerful tool for studying rarefied gas flows. However, the DSMC to be effective, cell size must smaller than mean free path, and time step collision time. These constraints make it difficult use in multiscale Over past decade, particle Fokker-Planck (FP) been studied address computational cost issues near-continuum regime. To capture main features of Boltzmann equation, various FP models have proposed, such as quadratic entropic...

The Boltzmann equation provides a statistical description of dilute gas, which is valid from the continuum to free molecular regime. Direct Simulation Monte Carlo (DSMC) method has been extensively used obtain numerical solution equation. However, DSMC becomes prohibitively expensive in low Knudsen number regime due lot collisions. particle-based Fokker-Planck studied reduce computational cost method. operator approximates discrete collision process as convection-diffusion velocity space. A...

The direct simulation Monte Carlo (DSMC) method has become a standard numerical technique for rarefied gas flows. However, its computational cost becomes prohibitive in the near-continuum regime. To enable efficient of multiscale flows, particle-based Fokker–Planck (FP) been studied. While several monatomic and diatomic FP models have proposed, extension to mixtures received little attention. This paper aims construct Master (FPM) equation mixtures, including energy exchange between...

An electrospray thruster is an electrostatic propulsion system that employs ionic liquids as propellant. Its ion beam consists of single ions and clusters, each cluster comprising a attached to one or more neutral liquid molecules. Due its meta-stability, the can fragment into less massive molecules during emission. This fragmentation alters overall plume composition, significantly affecting oscillation, which plays key role in neutralization. study aims analyze changes oscillation caused by...

The stochastic particle Fokker–Planck (FP) method has been gaining increasing attention in the field of rarefied gas dynamics due to its potential reduce computational costs direct simulation Monte Carlo method. FP approximates discrete binary collisions Boltzmann equation as continuous drift–diffusion phenomena velocity space. Consistency between and is achieved by matching production terms. Maxwell molecular model widely used this process possibility obtaining closed-form solutions for...

A residual atmosphere of the Very-Low-Earth-Orbit (VLEO) could be source drag force. The Atmosphere-Breathing Electric Propulsion (ABEP) system has been proposed to compensate force using as a propellant. ABEP requires an intake device that collects particles and delivers them discharge chamber. In this study, design parameters such geometry, gas-surface interaction (GSI) models, surface temperature, aspect ratio are examine performance at VLEO. diffuse GSI model is considered realistic due...

During atmospheric reentry, the vehicle surface is exposed to highly non-equilibrium flow. The can experience heterogeneous recombination of reactive atoms, which contributes its aerothermodynamic heating. This process followed by chemical energy accommodation (CEA), where released either transferred or internal modes recombined molecule. Heterogeneous be categorized into Eley–Rideal (ER) and Langmuir–Hinshelwood mechanisms, differ in their methods molecule formation degrees CEA. complete...

Motivated by improving the performance of particle-based Monte-Carlo simulations in transitional regime, Fokker–Planck kinetic models have been devised and studied as approximations Boltzmann collision operator. By generalizing linear drift model, cubic (cubic-FP) ellipsoidal (ES-FP) proposed, order to obtain correct Prandtl number for a dilute monatomic gas. This study provides close comparison between both low Mach supersonic settings. While direct simulation (DSMC) here serves benchmark,...

To simulate multiscale gas flow with solid particles, Burt's model, based on the Direct Simulation Monte Carlo (DSMC) framework, is widely used to predict gas–solid interactions under assumption of a negligibly small particle diameter compared local mean free path. However, model could become inaccurate when large relative This study introduces Gas–Solid Synchronous (GSS) which predicts in continuum regions without assuming regime around particle. Similar GSS includes gas-to-solid and...

Abstract The plasma plume flow of an atomic oxygen-fed (AO-fed) ion thruster is numerically investigated as a simplification the atmosphere-breathing electric propulsion (ABEP). A predictive analysis conducted focusing on backflow phenomenon and plume-background interaction in very-low-earth-orbit (VLEO). computational framework employs two sequentially integrated numerical methods: zero-dimensional (0-D) analytical model for radio-frequency hybrid method particle-in-cell (PIC) direct...

일반적으로 Navier-Stokes-Fourier 방정식에 근거한 Computational Fluid Dynamics (CFD) 방법은 연속체 영역에 적용되고, Boltzmann Direct Simulation Monte Carlo (DSMC) 희박기체 적용된다. 하지만 재진입 비행체와 같이 공기역학의 많은 문제는 국소적으로 밀도가 크게 변하는 멀티-스케일 희박 유동으로 알려져 있다. 유동에 대해서는 CFD 방법만으로는 정확도 측면에서 한계가 있고, DSMC 효율성 제한이 최근 CFD와 사이의 격차를 메우기 위해 대안적인 입자 시뮬레이션 기법들이 제시되고 가장 활발히 연구되고 있는 대상은 Bhatnagar-Gross-Krook (BGK) 방법과 Fokker-Planck (FP) 방법이 수치 방법들의 성능을 일관성 있게 평가하는 비교 연구는 아직 부족한 상황이다. 본 연구에서는 유동 해석에 대해 CFD, DSMC, BGK, FP 방법을 적용하고 분석하였다.

This study examines a new hybrid particle scheme used as an alternative means of multiscale flow simulation. The employs the direct simulation Monte Carlo (DSMC) method in rarefied regions and low diffusion (LD) continuum regions. numerical procedures are implemented within existing DSMC algorithm. performance LD‐DSMC approach is assessed by studying Mach 10 nitrogen over sphere with global Knudsen number 0.002. results show good overall agreement from standard CFD computation. Subcell...