scholarly journals Analysis of Nonisothermal Rarefied Gas Flow in Diverging Microchannels for Low-Pressure Microresistojets

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Daduí C. Guerrieri ◽  
Angelo Cervone ◽  
Eberhard Gill
Keyword(s):  
Power Consumption ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Specific Impulse ◽  
Three Dimensional ◽  
Working Fluid ◽  
Low Thrust ◽  
Channel Geometry ◽  
Rarefied Flow ◽  
The Impact

Heat transfer and fluid flow through different microchannel geometries in the transitional regime (rarefied flow) are analyzed by means of direct simulation Monte Carlo (DSMC) simulations. Four types of three-dimensional microchannels, intended to be used as expansion slots in microresistojet concepts, are investigated using nitrogen as working fluid. The main purpose is to understand the impact of the channel geometry on the exit velocity and the transmission coefficient, parameters which are well known to affect directly the thruster performance. Although this analysis can be applied in principle to several possible microfluidics scenarios, particular focus is given to its application in the field of space propulsion for micro-, nano-, and picosatellites, for which the requirements ask for low thrust levels from some micronewtons to a few millinewtons and moderate specific impulse, as well as a low power consumption in the order of a few watts. Analysis shows that the thrust produced by one single microchannel can be increased by about 480% with a careful selection of the channel geometry, decreasing at the same time the specific impulse by just 5%, with a power consumption decrease of more than 66.7%.

scholarly journals DSMC Simulation of Rarefied Gas Flow over a Backward- Facing Step: Effect of Expansion ratio

2019 ◽  
Author(s):  
Deepak Nabapure ◽  
Pratijay Guha ◽  
K Ram Chandra Murthy
Keyword(s):  
Flow Field ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Expansion Ratio ◽  
Backward Facing Step ◽  
Rarefied Flow ◽  
Step Effect ◽  
Dsmc Simulation ◽  
Limiting Case

Numerical simulations have been performed to study the effect of expansion ratio on the hypersonic rarefied flow past a backward-facing step. The Direct Simulation Monte Carlo (DSMC) method is used for the present study. An opensource solver named dsmcFoam has been used for this purpose. The solver has been validated with well-established results from the literature and good agreement is found among them. Simulations have been carried out for expansion ratios (ER) of 2,4,6,8,10 in the transition regime. The different flow field properties such as velocity, pressure and temperature have been studied. The profiles have found to be influenced by the compressibility and rarefaction effects. Limiting case of ER=8 and above has no influence on the flow field properties.

scholarly journals Rarefied Poiseuille Flow in a Circular Tube

2019 ◽  
Vol 224 ◽  
pp. 02001
Author(s):  
Oksana Germider ◽  
Vasily Popov
Keyword(s):  
Kinetic Equation ◽  
Chebyshev Polynomials ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Circular Tube ◽  
Three Dimensional ◽  
Heat Fluxes ◽  
Model Kinetic Equation ◽  
Algebraic Equations ◽  
Rarefied Gas Flows

An isothermal rarefied gas flow through a long circular tube due to longitudinal pressure gradient (a three-dimensional Poiseuille problem) was studied using the linearized Bhatnagar-Gross-Krook model kinetic equation over the whole range of the Knudsen numbers covering both free molecular and hydrodynamic regimes. The solution of the model kinetic equation with the diffuse boundary condition is obtained by the collocation method. This approach is based on the Chebyshev polynomials and rational Chebyshev functions. Choosing the zeros of Chebyshev polynomials in the multivariate range of integration for the collocation points, we reduce this problem to a set of algebraic equations. Based on the proposed approach, we have calculated the mass and the heat fluxes through the tube. The obtained results have also been compared with other studies. The developed approach may also be applied to a more general class of problems of rarefied gas flows in microand nanotubes.

Efficient Deterministic Modelling of Three-Dimensional Rarefied Gas Flows

2012 ◽  
Vol 12 (1) ◽  
pp. 162-192 ◽  
Author(s):  
V. A. Titarev
Keyword(s):  
Gas Flow ◽  
Parallel Machines ◽  
High Efficiency ◽  
Rarefied Gas ◽  
Three Dimensional ◽  
Collision Integral ◽  
Gas Flows ◽  
Rarefied Gas Flows ◽  
Deterministic Modelling ◽  
Model Collision

AbstractThe paper is devoted to the development of an efficient deterministic framework for modelling of three-dimensional rarefied gas flows on the basis of the numerical solution of the Boltzmann kinetic equation with the model collision integrals. The framework consists of a high-order accurate implicit advection scheme on arbitrary unstructured meshes, the conservative procedure for the calculation of the model collision integral and efficient implementation on parallel machines. The main application area of the suggested methods is micro-scale flows. Performance of the proposed approach is demonstrated on a rarefied gas flow through the finite-length circular pipe. The results show good accuracy of the proposed algorithm across all flow regimes and its high efficiency and excellent parallel scalability for up to 512 cores.

The Study of Rarefied Gas Flow Through Microfilters With Different Openings Using MONIR-DSMC

2011 ◽  
Author(s):  
Masoud Darbandi ◽  
Abolfazl Karchani ◽  
Gerry Schneider
Keyword(s):  
Pressure Drop ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Medical Applications ◽  
Rarefied Gas Flow ◽  
Rarefied Flow ◽  
Particle Pairs ◽  
Hexagonal Hole ◽  
Flow Through ◽  
Opening Factor

The main objective of this work is to evaluate the pressure loss at low subsonic rarefied flow through a microfilter having different opening shapes. As is known, a filter with a lower pressure drop is more suitable for different industrial and medical applications. We use our own developed DSMC solver, i.e., 3D MONIR-DSMC code to lunch our study. MONIR uses the NTC (no-time-counter) scheme to model the collision process. The VHS model is also chosen to simulate collision between particle pairs. The Opening factor which is known as one of the most important parameters affecting the microfilter design, is taken constant. The results show that the pressure drop for a rectangular holes is greater than the other hole shapes. Also, the hexagonal hole shapes provide efficient manners compare with circular, rectangular and cubic hole shapes, considering constant opening factor and hydraulic diameter magnitudes.

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