scholarly journals Extended Macroscopic Study of Dilute Gas Flow within a Microcavity

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Mohamed Hssikou ◽  
Jamal Baliti ◽  
Mohammed Alaoui
Keyword(s):  
Constant Velocity ◽  
Gas Flow ◽  
Continuum Theory ◽  
Point Of View ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Moment Equations ◽  
Macroscopic Theory ◽  
Dilute Gas ◽  
Opposite Motion

The behaviour of monatomic and dilute gas is studied in the slip and early transition regimes using the extended macroscopic theory. The gas is confined within a two-dimensional microcavity where the longitudinal sides are in the opposite motion with constant velocity ±Uw. The microcavity walls are kept at the uniform and reference temperature T0. Thus, the gas flow is transported only by the shear stress induced by the motion of upper and lower walls. From the macroscopic point of view, the regularized 13-moment equations of Grad, R13, are solved numerically. The macroscopic gas proprieties are studied for different values of the so-called Knudsen number (Kn), which gives the gas-rarefaction degree. The results are compared with those obtained using the classical continuum theory of Navier-Stokes and Fourier (NSF).

TRIGGERING OF DETONATION PROCESSES IN PROPULSION CHAMBER

2021 ◽  
Vol 14 (2) ◽  
pp. 40-45
Author(s):  
D. V. VORONIN ◽  
Keyword(s):  
Thermal Conductivity ◽  
Numerical Modeling ◽  
Gas Flow ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Navier Stokes Equations ◽  
Chemically Reacting ◽  
Plane Disk ◽  
And Diffusion

The Navier-Stokes equations have been used for numerical modeling of chemically reacting gas flow in the propulsion chamber. The chamber represents an axially symmetrical plane disk. Fuel and oxidant were fed into the chamber separately at some angle to the inflow surface and not parallel one to another to ensure better mixing of species. The model is based on conservation laws of mass, momentum, and energy for nonsteady two-dimensional compressible gas flow in the case of axial symmetry. The processes of viscosity, thermal conductivity, turbulence, and diffusion of species have been taken into account. The possibility of detonation mode of combustion of the mixture in the chamber was numerically demonstrated. The detonation triggering depends on the values of angles between fuel and oxidizer jets. This type of the propulsion chamber is effective because of the absence of stagnation zones and good mixing of species before burning.

scholarly journals Continuum Analysis of Rarefaction Effects on a Thermally Induced Gas Flow

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Mohamed Hssikou ◽  
Jamal Baliti ◽  
Mohammed Alaoui
Keyword(s):  
Knudsen Number ◽  
Gas Flow ◽  
Flow Behavior ◽  
Continuum Theory ◽  
Velocity Slip ◽  
Nonlinear Effects ◽  
Point Of View ◽  
Heating Rates ◽  
Micro Cavity ◽  
Maxwell Gas

A Maxwell gas confined within a micro cavity with nonisothermal walls is investigated in the slip and early transition regimes using the classical and extended continuum theories. The vertical sides of the cavity are kept at the uniform and environmental temperature T0, while the upper and bottom ones are linearly heated in opposite directions from the cold value T0 to the hot one TH. The gas flow is, therefore, induced only by the temperature gradient created along the longitudinal walls. The problem is treated from a macroscopic point of view by solving numerically the so-called regularized 13-moment equations (R13) recently developed as an extension of Grad 13-moment theory to the third order of the Knudsen number powers in the Chapman-Enskog expansion. The gas macroscopic properties obtained by this method are compared with the classical continuum theory results (NSF) using the first and second order of velocity slip and temperature jump boundary conditions. The gas flow behavior is studied as a function of the Knudsen number (Kn), nonlinear effects, for different heating rates T0/TH. The micro cavity aspect ratio effect is also evaluated on the flow fields in this study.

scholarly journals Lattice Boltzmann accelerated direct simulation Monte Carlo for dilute gas flow simulations

2016 ◽  
Vol 374 (2080) ◽  
pp. 20160226 ◽  
Author(s):  
G. Di Staso ◽  
H. J. H. Clercx ◽  
S. Succi ◽  
F. Toschi
Keyword(s):  
Monte Carlo ◽  
Lattice Boltzmann ◽  
Gas Flow ◽  
Direct Simulation Monte Carlo ◽  
Bulk Flow ◽  
Navier Stokes ◽  
Direct Simulation ◽  
Dilute Gas ◽  
Simulation Monte Carlo ◽  
Non Equilibrium

Hybrid particle–continuum computational frameworks permit the simulation of gas flows by locally adjusting the resolution to the degree of non-equilibrium displayed by the flow in different regions of space and time. In this work, we present a new scheme that couples the direct simulation Monte Carlo (DSMC) with the lattice Boltzmann (LB) method in the limit of isothermal flows. The former handles strong non-equilibrium effects, as they typically occur in the vicinity of solid boundaries, whereas the latter is in charge of the bulk flow, where non-equilibrium can be dealt with perturbatively, i.e. according to Navier–Stokes hydrodynamics. The proposed concurrent multiscale method is applied to the dilute gas Couette flow, showing major computational gains when compared with the full DSMC scenarios. In addition, it is shown that the coupling with LB in the bulk flow can speed up the DSMC treatment of the Knudsen layer with respect to the full DSMC case. In other words, LB acts as a DSMC accelerator. This article is part of the themed issue ‘Multiscale modelling at the physics–chemistry–biology interface’.

Heat and Mass Transfer of a Rarefied Gas in a Driven Micro-Cavity

2009 ◽  
Author(s):  
X. J. Gu ◽  
B. John ◽  
G. H. Tang ◽  
D. R. Emerson
Keyword(s):  
Gas Flow ◽  
Rarefied Gas ◽  
Transport Model ◽  
Direct Simulation Monte Carlo ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Order Moment ◽  
Moment Equations ◽  
Micro Cavity ◽  
Non Equilibrium

A high-order moment method is employed to construct the transport model for non-equilibrium gas flow in micro-scale geometries. The motion of a gas in a two-dimensional square micro-cavity is solved using the 26 moment equations for low Reynolds and Mach number flows in the early transition regime. The computed velocity and temperature fields are compared with data obtained from the direct simulation Monte Carlo method. It is found that the 26 moment equations are able to capture the non-equilibrium phenomena in a driven micro-cavity, such as counter-gradient heat transfer, which are not embedded in the Navier-Stokes-Fourier equations.

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