Numerical Study of Plasma Flow Around a Reentry Vehicle During Atmospheric Reentry With an Unstructured Grid Solver

2015 ◽  
Author(s):  
Reo Nakasato ◽  
Yusuke Takahashi ◽  
Nobuyuki Oshima
Keyword(s):  
Shock Wave ◽  
Plasma Flow ◽  
Shock Layer ◽  
Electromagnetic Waves ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Aerodynamic Heating ◽  
Accurate Evaluation ◽  
Reentry Vehicle ◽  
Atmospheric Reentry

When a reentry vehicle enters the planetary atmosphere, a strong shock wave is generated and the strong aerodynamic heating appears. Gas temperature in front of the vehicle exceeds 10,000K and chemical reactions (ionizations and dissociations) occur behind the shock wave. Because the reentry vehicle is damaged by the aerodynamic heating, accurate evaluation of the aerodynamic heating in the high-enthalpy flow is necessary for the design and the development of the vehicle. The communication blackout phenomenon which prevents the propagation of the electromagnetic waves can occur by the characteristics of electrons in the shock layer to absorb and reflect the electromagnetic waves. To estimate the communicationable time and understand the behavior of the electromagnetic waves around the vehicle, the accurate evaluation of the plasma flow around the vehicle is also necessary. In this study, the three-dimensional numerical analysis was conducted to consider an angle of attack by using the analysis software for compressible fluid, RG-FaSTAR which has been developed by JAXA. Moreover, unstructured grids were used to make it easier to generate computational grid around the vehicle with complicated shape. Note that RG-FaSTAR is a version of FaSTAR (FaST Aerodynamic Routine) installing the real gas effect. We reproduced the actual flow field around the Atmospheric Reentry Demonstrator (ARD) which was launched by the European Space Agency (ESA) in 1998 and revealed the aerodynamic heating and plasma flow properties during atmospheric reentry. The computational result showed good agreement with measured pressure coefficient at the stagnation point. In addition, the features of the shock layer and the rear region around ARD were revealed.

Numerical investigations on the effect of volute casing treatment for performance augmentation in a centrifugal fan

2021 ◽  
pp. 095440622110341
Author(s):  
Manjunath L Nilugal ◽  
K Vasudeva Karanth ◽  
Madhwesh N
Keyword(s):  
Total Pressure ◽  
Static Pressure ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Centrifugal Fan ◽  
Casing Treatment ◽  
Sliding Mesh ◽  
Optimum Configuration

This article presents the effect of volute chamfering on the performance of a forward swept centrifugal fan. The numerical analysis is performed to obtain the performance parameters such as static pressure rise coefficient and total pressure coefficient for various flow coefficients. The chamfer ratio for the volute is optimized parametrically by providing a chamfer on either side of the volute. The influence of the chamfer ratio on the three dimensional flow domain was investigated numerically. The simulation is carried out using Re-Normalisation Group (RNG) k-[Formula: see text] turbulence model. The transient simulation of the fan system is done using standard sliding mesh method available in Fluent. It is found from the analysis that, configuration with chamfer ratio of 4.4 is found be the optimum configuration in terms of better performance characteristics. On an average, this optimum configuration provides improvement of about 6.3% in static pressure rise coefficient when compared to the base model. This optimized chamfer configuration also gives a higher total pressure coefficient of about 3% validating the augmentation in static pressure rise coefficient with respect to the base model. Hence, this numerical study establishes the effectiveness of optimally providing volute chamfer on the overall performance improvement of forward bladed centrifugal fan.

scholarly journals Numerical Study on Damage Zones Induced by Excavation and Ventilation in a High-Temperature Tunnel at Depth

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4773
Author(s):  
Jianyu Li ◽  
Hong Li ◽  
Zheming Zhu ◽  
Ye Tao ◽  
Chun’an Tang
Keyword(s):  
High Temperature ◽  
Lateral Pressure ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Fracture Morphology ◽  
In Situ Stress ◽  
Surrounding Rock ◽  
Geothermal System ◽  
Mechanical Coupling ◽  
Lateral Pressure Coefficient

Geothermal power is being regarded as depending on techniques derived from hydrocarbon production in worldwide current strategy. However, it has artificially been developed far less than its natural potentials due to technical restrictions. This paper introduces the Enhanced Geothermal System based on Excavation (EGS-E), which is an innovative scheme of geothermal energy extraction. Then, based on cohesion-weakening-friction-strengthening model (CWFS) and literature investigation of granite test at high temperature, the initiation, propagation of excavation damaged zones (EDZs) under unloading and the EDZs scale in EGS-E closed to hydrostatic pressure state is studied. Finally, we have a discussion about the further evolution of surrounding rock stress and EDZs during ventilation is studied by thermal-mechanical coupling. The results show that the influence of high temperature damage on the mechanical parameters of granite should be considered; Lateral pressure coefficient affects the fracture morphology and scale of tunnel surrounding rock, and EDZs area is larger when the lateral pressure coefficient is 1.0 or 1.2; Ventilation of high temperature and high in-situ stress tunnel have a significant effect on the EDZs scale; Additional tensile stress is generated in the shallow of tunnel surrounding rock, and the compressive stress concentration transfers to the deep. EDZs experiences three expansion stages of slow, rapid and deceleration with cooling time, and the thermal insulation layer prolongs the slow growth stage.

scholarly journals Adaptation of the de Hoffmann–Teller frame for quasi-perpendicular collisionless shocks

2015 ◽  
Vol 33 (3) ◽  
pp. 345-350 ◽  
Author(s):  
H. Comişel ◽  
Y. Narita ◽  
U. Motschmann
Keyword(s):  
Shock Wave ◽  
Electric Field ◽  
Shock Layer ◽  
Local Magnetic Field ◽  
Sliding Velocity ◽  
Collisionless Shock ◽  
Collisionless Shocks ◽  
Particle In Cell ◽  
Cell Simulation ◽  
High Mach

Abstract. The concept of the de Hoffmann–Teller frame is revisited for a high Mach-number quasi-perpendicular collisionless shock wave. Particle-in-cell simulation shows that the local magnetic field oscillations in the shock layer introduce a residual motional electric field in the de Hoffmann–Teller frame, which is misleading in that one may interpret that electrons were not accelerated but decelerated in the shock layer. We propose the concept of the adaptive de Hoffmann–Teller (AHT) frame in which the residual convective field is canceled by modulating the sliding velocity of the de Hoffmann–Teller frame. The electrostatic potential evaluated by Liouville mapping supports the potential profile obtained by electric field in this adaptive frame, offering a wide variety of applications in shock wave studies.

Numerical Study of the Shock Wave Propagation in a Micron-Scale Contracting Channel

2011 ◽  
Author(s):  
G. V. Shoev ◽  
Ye. A. Bondar ◽  
D. V. Khotyanovsky ◽  
A. N. Kudryavtsev ◽  
G. Mirshekari ◽  
...  
Keyword(s):  
Shock Wave ◽  
Wave Propagation ◽  
Numerical Study ◽  
Shock Wave Propagation
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