scholarly journals Comparison of numerical predictions of the supersonic expansion inside micronozzles of micro–resistojets

2019 ◽  
Vol 304 ◽  
pp. 02012
Author(s):  
Maria Grazia De Giorgi ◽  
Donato Fontanarosa ◽  
Antonio Ficarella

The present work provides a numerical investigation of the supersonic flow inside a planar micronozzle configuration under different gas rarefaction conditions. Two different propellants have been considered, namely water vapor and nitrogen, which relate to their use in VLMs (the former) and cold gas microthrusters (the latter), respectively. Furthermore, two different numerical approaches have been used due to the different gas rarefaction regime, i.e. the typical continuum Navier–Stokes with partial slip assumption at walls and the particle–based Direct Simulation Monte Carlo (DSMC) technique. As a result, under high–pressure operating conditions, both water and nitrogen flows supersonically expanded into the micronozzle without chocking in combination with a linear growth of the boundary layer on walls. However, when low–pressure operating condition are imposed and a molecular regime is established inside the micronozzle, a very rapid expansion occurred close to the nozzle exit in combination with a strong chocking of the flow and a micronozzle quality reduction of about 40%. Furthermore, water exhibited specific higher specific impulse than nitrogen above 60%.

2009 ◽  
Vol 623 ◽  
pp. 387-411 ◽  
Author(s):  
VICENTE GARZÓ ◽  
FRANCISCO VEGA REYES ◽  
JOSÉ MARÍA MONTANERO

We evaluate in this work the hydrodynamic transport coefficients of a granular binary mixture in d dimensions. In order to eliminate the observed disagreement (for strong dissipation) between computer simulations and previously calculated theoretical transport coefficients for a monocomponent gas, we obtain explicit expressions of the seven Navier–Stokes transport coefficients by the use of a new Sonine approach in the Chapman–Enskog (CE) theory. This new approach consists of replacing, where appropriate in the CE procedure, the Maxwell–Boltzmann distribution weight function (used in the standard first Sonine approximation) by the homogeneous cooling state distribution for each species. The rationale for doing this lies in the well-known fact that the non-Maxwellian contributions to the distribution function of the granular mixture are more important in the range of strong dissipation we are interested in. The form of the transport coefficients is quite common in both standard and modified Sonine approximations, the distinction appearing in the explicit form of the different collision frequencies associated with the transport coefficients. Additionally, we numerically solve by the direct simulation Monte Carlo method the inelastic Boltzmann equation to get the diffusion and the shear viscosity coefficients for two and three dimensions. As in the case of a monocomponent gas, the modified Sonine approximation improves the estimates of the standard one, showing again the reliability of this method at strong values of dissipation.


2011 ◽  
Vol 110-116 ◽  
pp. 2491-2496
Author(s):  
Sourabh Jain ◽  
Prabhu Ramachandran

Rarefied flows cannot be accurately simulated using Navier-Stokes (N-S) equations. The Direct Simulation Monte-Carlo (DSMC) technique is a particle based method for accurate simulation of flows under such conditions. A DSMC code is developed using an object-oriented (OO) approach which can simulate flows around arbitrary shapes. Hence, the flux from such boundaries can be correctly predicted. The object-oriented approach enables for easy modification of the code. For example, it is easy to use different collision models to implement different relaxation algorithm. The code is validated for the one-dimensional Fourier heat conduction problem. Results for the development of a shock due to supersonic flow over a 15 degree wedge are also presented. Inclined boundary of the wedge is correctly captured as the particles interact with the the exact shape of the boundary. Shock angle is found more than expected due to rarefaction effects.


2016 ◽  
Vol 22 (4) ◽  
Author(s):  
Mohamed Hssikou ◽  
Jamal Baliti ◽  
Mohammed Alaoui

AbstractThe steady state of a dilute gas enclosed within a rectangular cavity, whose upper and lower sides are in relative motion, is considered in the slip and early transition regimes. The DSMC (Direct simulation Monte Carlo) method is used to solve the Boltzmann equation for analysing a Newtonian viscous heat conducting ideal gas with the slip and jump boundary conditions (SJBC) in the vicinity of horizontal walls. The numerical results are compared with the Navier–Stokes solutions, with and without SJBC, through the velocity, temperature, and normal heat flux profiles. The parallel heat flux and shear stress are also evaluated as a function of rarefaction degree; estimated by the Knudsen number


AIAA Journal ◽  
2003 ◽  
Vol 41 (6) ◽  
pp. 1055-1063 ◽  
Author(s):  
Christopher J. Roy ◽  
Michael A. Gallis ◽  
Timothy J. Bartel ◽  
Jeffrey L. Payne

Author(s):  
H. Futagami ◽  
H. Ninokata

Behaviors inside rotating cylinders where the range of operating pressure is very wide, i.e. from subatmospheric to almost vacuum are subject of this study. The flow near the rotating axis is very rarefied. If a flow becomes rarefied, the flow cannot be treated as that of a continuum media. Therefore the flow cannot be analyzed by the method based on solving Navier-Stokes equation. One of the promising methods is considered to be DSMC (Direct Simulation Monte Carlo) method based on Boltzmann equation ([1]). In this paper, fundamental validation analyses related to isotope separation in a rotating cylinder calculations of endplate type centrifuge were performed for the parametric study, with DSMC. The results were compared with the experimental results by Groth et al ([2]). The validity of the calculations and its limit were also discussed.


AIAA Journal ◽  
1994 ◽  
Vol 32 (7) ◽  
pp. 1399-1406 ◽  
Author(s):  
James N. Moss ◽  
Robert A. Mitcheltree ◽  
Virendra K. Dogra ◽  
Richard G. Wilmoth

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