scholarly journals Effect of viscosity on slip boundary conditions in rarefied gas flows

2019 ◽  
Author(s):  
Nam T. P. Le
Keyword(s):  
Slip Velocity ◽  
Rarefied Gas ◽  
Cross Flow ◽  
Navier Stokes ◽  
Gas Flows ◽  
Gas Temperature ◽  
Slip Boundary ◽  
Rarefied Gas Flows ◽  
Viscosity Models ◽  
Simulation Results

The viscosity of gases plays an important role in the kinetic theory of gases and in the continuum-fluid modeling of the rarefied gas flows. In this paper we investigate the effect of the gas viscosity on the surface properties as surface gas temperature and slip velocity in rarefied gas simulations. Three various viscosity models in the literature such as the Maxwell, Power Law and Sutherland models are evaluated. They are implemented into OpenFOAM to work with the solver “rhoCentralFoam” that solves the Navier-Stokes-Fourier equations. Four test cases such as the pressure driven backward facing step nanochannel, lid-driven micro-cavity, hypersonic gas flows past the sharp 25-55-deg. biconic and the circular cylinder in cross-flow cases are considered for evaluating three viscosity models. The simulation results show that, whichever the first-order or second-order slip and jump conditions are adopted, the simulation results of the surface temperature and slip velocity using the Maxwell viscosity model give good agreement with DSMC data for all cases studied.

Numerical Simulation and Modeling of Laminar Developing Flow in Channels and Tubes With Slip

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Y. S. Muzychka ◽  
R. Enright
Keyword(s):  
Stokes Equations ◽  
Rarefied Gas ◽  
Slip Boundary Condition ◽  
Momentum Equation ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Navier Stokes Equations ◽  
Navier Slip ◽  
Slip Boundary ◽  
Rarefied Gas Flows

Analytical solutions for slip flows in the hydrodynamic entrance region of tubes and channels are examined. These solutions employ a linearized axial momentum equation using Targ's method. The momentum equation is subjected to a first order Navier slip boundary condition. The accuracy of these solutions is examined using computational fluid dynamics (CFD) simulations. CFD simulations utilized the full Navier–Stokes equations, so that the implications of the approximate linearized axial momentum equation could be fully assessed. Results are presented in terms of the dimensionless mean wall shear stress, τ⋆, as a function of local dimensionless axial coordinate, ξ, and relative slip parameter, β. These solutions can be applied to either rarefied gas flows when compressibility effects are small or apparent liquid slip over hydrophobic and superhydrophobic surfaces. It has been found that, under slip conditions, the minimum Reynolds number should be ReDh>100 in order for the approximate linearized solution to remain valid.

scholarly journals New exact solutions for microscale gas flows

2021 ◽  
Vol 128 (1) ◽  
Author(s):  
Hollis Williams
Keyword(s):  
Heat Source ◽  
Exact Solutions ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Gas Flows ◽  
Point Heat Source ◽  
Slip Boundary ◽  
Rarefied Gas Flows ◽  
New Exact Solutions ◽  
Dependent Point

AbstractWe present a number of exact solutions to the linearised Grad equations for non-equilibrium rarefied gas flows and heat flows. The solutions include the flow and pressure fields associated to a point force placed in a rarefied gas flow close to a no-slip boundary and the temperature field for a point heat source placed in a heat flow close to a temperature jump boundary. We also derive the solution of the unsteady Grad equations in one dimension with a time-dependent point heat source term and the Grad analogue of the rotlet, a well-known singularity of Stokes flow which corresponds to a point torque.

Shock polar investigation in supersonic rarefied gas flows over a circular cylinder

2021 ◽  
Vol 33 (5) ◽  
pp. 052006
Author(s):  
Hassan Akhlaghi ◽  
Ehsan Roohi ◽  
Abbas Daliri ◽  
Mohammad-Reza Soltani
Keyword(s):  
Circular Cylinder ◽  
Rarefied Gas ◽  
Gas Flows ◽  
Rarefied Gas Flows

scholarly journals Rarefied gas flows through meshes and implications for atmospheric measurements

2001 ◽  
Vol 19 (5) ◽  
pp. 563-569 ◽  
Author(s):  
J. Gumbel
Keyword(s):  
Middle Atmosphere ◽  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Atmospheric Composition ◽  
Gas Flows ◽  
Atmospheric Measurements ◽  
Rarefied Gas Flows ◽  
Flow Disturbances ◽  
Composition And Structure ◽  
Compression Effects

Abstract. Meshes are commonly used as part of instruments for in situ atmospheric measurements. This study analyses the aerodynamic effect of meshes by means of wind tunnel experiments and numerical simulations. Based on the Direct Simulation Monte Carlo method, a simple mesh parameterisation is described and applied to a number of representative flow conditions. For open meshes freely exposed to the flow, substantial compression effects are found both upstream and downstream of the mesh. Meshes attached to close instrument structures, on the other hand, cause only minor flow disturbances. In an accompanying paper, the approach developed here is applied to the quantitative analysis of rocket-borne density measurements in the middle atmosphere.Key words. Atmospheric composition and structure (instruments and techniques; middle atmosphere – composition and chemistry)

scholarly journals An open source, parallel DSMC code for rarefied gas flows in arbitrary geometries

2010 ◽  
Vol 39 (10) ◽  
pp. 2078-2089 ◽  
Author(s):  
T.J. Scanlon ◽  
E. Roohi ◽  
C. White ◽  
M. Darbandi ◽  
J.M. Reese
Keyword(s):  
Open Source ◽  
Rarefied Gas ◽  
Gas Flows ◽  
Rarefied Gas Flows ◽  
Arbitrary Geometries
Sign in / Sign up

Export Citation Format

Share Document