Effect of boundary-layer injection on the drag of an axisymmetric body in a hypersonic imperfect-gas flow

1982 ◽  
Vol 42 (5) ◽  
pp. 510-513 ◽  
Author(s):  
V. I. Timoshenko
Keyword(s):  
Boundary Layer ◽  
Gas Flow ◽  
Axisymmetric Body ◽  
Imperfect Gas

TO THE THEORY OF UNSTEADY SEPARATION AND INTERACTION OF BOUNDARY LAYER WITH SUPERSONIC GAS FLOW

2018 ◽  
Vol 49 (4) ◽  
pp. 415-427
Author(s):  
Igor Ivanovich Lipatov ◽  
Vladimir Yakovlevich Neiland
Keyword(s):  
Boundary Layer ◽  
Gas Flow ◽  
Unsteady Separation ◽  
Supersonic Gas Flow

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.

Application of CFD-DSMC coupling method in micro-scale gas flow and combustion

2020 ◽  
Vol 34 (27) ◽  
pp. 2050301
Author(s):  
Shaoyi Suo ◽  
Linsong Jiang ◽  
Maozhao Xie
Keyword(s):  
Boundary Layer ◽  
Chemical Reaction ◽  
Wall Temperature ◽  
Slip Velocity ◽  
Gas Flow ◽  
Wall Slip ◽  
Reaction Products ◽  
Microscopic Method ◽  
Flow Heat ◽  
The Impact

The reversible elementary reaction mechanism of six components and seven steps of H2/O2 are applied by using a CFD-DSMC coupling iteration method to study the impact of boundary on flow, heat transfer and chemical reaction in a microtube. The microtube consists of a converging section and a straight section, which represents the gap on the contact surface of the pellets in porous media. It shows that after coupling, with the designed conditions in this paper, the influence of wall temperature is more obvious than that of wall slip velocity on the coupling results from the analysis of chemical reaction, yet the velocity field in the boundary layer is more affected by the wall slip velocity. In addition, the velocity in the central region of the flow decreases while the concentration of reaction products increases after coupling, due to the increasing of the velocity in the boundary layer and the influence of wall temperature, respectively. By the coupling of CFD-DSMC methods, more details and influence of the boundary can be considered, and the computational efficiency is higher than that of the single microscopic method.

Experimental Study on Pressure Fluctuations in the Boundary Layer of an Axisymmetric Body

2011 ◽  
Vol 66-68 ◽  
pp. 1488-1493
Author(s):  
Hong Xiao ◽  
Chao Gao ◽  
Zhen Kun Ma
Keyword(s):  
Boundary Layer ◽  
Experimental Study ◽  
Mach Number ◽  
Dynamic Pressure ◽  
Pressure Fluctuations ◽  
Axisymmetric Body ◽  
Pressure Measurements ◽  
Fluctuating Pressure ◽  
Frequency Domains ◽  
Dynamic Pressure Measurements

The characteristics of the fluctuating pressure in the boundary layer of an axisymmetric body have been investigated experimentally using dynamic pressure measurements and Schlieren photograghs. Data were acquired at subsonic and super-sonic Mach numbers. The angles of attack ranged from 0° to 5°. Pressure signals were measured simultaneously in several positions along the model and were analyzed both in the time and frequency domains. The Mach number shows the relevant influence on . Furthermore, the pressure fluctuations’ level decreases with the increasing of Mach number except M=1.15. And it is shown that, the location along the axis of the model and the angles of attack have small effect on pressure fluctuations.

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