Rarefied Couette flows performance in micro fluid machinery based on improved DSMC method

2014 ◽  
Author(s):  
Jianjun Ye ◽  
Dandan Liu ◽  
Jian Yang ◽  
Jun Wang ◽  
Peng Duan
Keyword(s):  
Fluid Machinery ◽  
Dsmc Method

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.

scholarly journals Special Issue on “CFD Based Researches and Applications for Fluid Machinery and Fluid Device”

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1137
Author(s):  
Jin-Hyuk Kim ◽  
Sung-Min Kim ◽  
Minsuk Choi ◽  
Lei Tan ◽  
Bin Huang ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Power System ◽  
Special Issue ◽  
Numerical Techniques ◽  
Fluid Machinery ◽  
Computing Power ◽  
Computational Fluid Dynamics Cfd

The demand for computational fluid dynamics (CFD)-based numerical techniques is increasing rapidly with the development of the computing power system [...]

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.

Numerical Simulation of Chemical Reactions on Rarefied Plasma Plume by DSMC Method

2021 ◽  
Vol 49 (3) ◽  
pp. 1214-1226
Author(s):  
Yongyuan Su ◽  
Jie Li ◽  
Haoyu Wang ◽  
Ao Xu
Keyword(s):  
Numerical Simulation ◽  
Chemical Reactions ◽  
Plasma Plume ◽  
Dsmc Method

Numerical Analysis of Influence of Roughness of Material Surface on High-Speed Liquid Droplet Impingement

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Hirotoshi Sasaki ◽  
Yuka Iga
Keyword(s):  
Numerical Analysis ◽  
High Speed ◽  
Erosion Rate ◽  
Liquid Droplet ◽  
Material Surface ◽  
Liquid Droplets ◽  
Fluid Machinery ◽  
Droplet Impingement ◽  
Surface Liquid ◽  
Droplet Impingement Erosion

This study explains why the deep erosion pits are formed in liquid droplet impingement erosion even though the droplets uniformly impinge on the entire material surface. Liquid droplet impingement erosion occurs in fluid machinery on which droplets impinge at high speed. In the process of erosion, the material surface becomes completely roughened by erosion pits. In addition, most material surface is not completely smooth and has some degree of initial roughness from manufacturing and processing and so on. In this study, to consider the influence of the roughness on the material surface under droplet impingement, a numerical analysis of droplets impinging on the material surface with a single wedge and a single bump was conducted with changing offsets between the droplet impingement centers and the roughness centers on each a wedge bottom and a bump top. As results, two mechanisms are predicted from the present numerical results: the erosion rate accelerates and transitions from the incubation stage to the acceleration stage once roughness occurs on the material surface; the other is that deep erosion pits are formed even in the case of liquid droplets impinging uniformly on the entire material surface.

Study of Gas Flow in Micronozzles Using an Unstructured DSMC Method

2009 ◽  
Author(s):  
Ehsan Roohi ◽  
Masoud Darbandi ◽  
Vahid Mirjalili
Keyword(s):  
Boundary Layer ◽  
Knudsen Number ◽  
Gas Flow ◽  
Subsonic Flow ◽  
Flow Behavior ◽  
Boundary Layer Separation ◽  
Back Pressure ◽  
Viscous Force ◽  
Dsmc Method ◽  
Wide Range

The current research uses an unstructured direct simulation Monte Carlo (DSMC) method to numerically investigate supersonic and subsonic flow behavior in micro convergent–divergent nozzle over a wide range of rarefied regimes. The current unstructured DSMC solver has been suitably modified via using uniform distribution of particles, employing proper subcell geometry, and benefiting from an advanced molecular tracking algorithm. Using this solver, we study the effects of back pressure, gas/surface interactions (diffuse/specular reflections), and Knudsen number, on the flow field in micronozzles. We show that high viscous force manifesting in boundary layers prevents supersonic flow formation in the divergent section of nozzles as soon as the Knudsen number increases above a moderate magnitude. In order to accurately simulate subsonic flow at the nozzle outlet, it is necessary to add a buffer zone to the end of nozzle. If we apply the back pressure at the outlet, boundary layer separation is observed and a region of backward flow appears inside the boundary layer while the core region of inviscid flow experiences multiple shock-expansion waves. We also show that the wall boundary layer prevents forming shocks in the divergent part. Alternatively, Mach cores appear at the nozzle center followed by bow shocks and an expansion region.

Research on CFD Simulation of the Cement Slurry Mixer

2012 ◽  
Vol 621 ◽  
pp. 196-199
Author(s):  
Shui Ping LI ◽  
Ya Li Yuan ◽  
Lu Gang Shi
Keyword(s):  
Flow Field ◽  
High Performance ◽  
Cfd Simulation ◽  
Structural Parameters ◽  
Internal Flow ◽  
Simulation Method ◽  
Cement Slurry ◽  
Fluid Machinery ◽  
Computational Fluid Dynamics Cfd ◽  
Machinery Design

Numerical simulation method of the internal flow field of fluid machinery has become an important technology in the study of fluid machinery design. In order to obtain a high-performance cement slurry mixer, computational fluid dynamics (CFD) techniques are used to simulate the flow field in the mixer, and the simulation results are studied. According to the analysis results, the structural parameters of the mixer are modified. The results show the mixer under the revised parameters meet the design requirements well. So CFD analysis method can shorten design period and provide valuable theoretical guidance for the design of fluid machinery.

Investigation of the effect of bellows on the separation power in a gas centrifuge using DSMC method

2022 ◽  
Vol 169 ◽  
pp. 108955
Author(s):  
Sadegh Yousefi-Nasab ◽  
Jaber Safdari ◽  
Javad Karimi-Sabet ◽  
Masoud Khajenoori ◽  
Mohamad hasan Mallah ◽  
...  
Keyword(s):  
Dsmc Method ◽  
Separation Power ◽  
Gas Centrifuge
Sign in / Sign up

Export Citation Format

Share Document