scholarly journals Effects of compressible flow phenomena on aerodynamic characteristics in Hyperloop system

2021 ◽  
pp. 106970
Author(s):  
Kyeong Sik Jang ◽  
Thi Thanh Giang Le ◽  
Jihoon Kim ◽  
Kwan-Sup Lee ◽  
Jaiyoung Ryu
Keyword(s):  
Compressible Flow ◽  
Aerodynamic Characteristics ◽  
Flow Phenomena

The Effect of Reynolds Number on the Aerodynamic Performance of Micro Radial Flow Fans

2005 ◽  
Author(s):  
K. Hanly ◽  
R. Grimes ◽  
E. Walsh ◽  
B. Rodgers ◽  
J. Punch
Keyword(s):  
Reynolds Number ◽  
Heat Dissipation ◽  
Radial Flow ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Fundamental Change ◽  
Geometric Similarity ◽  
Flow Phenomena ◽  
Conventional Cooling ◽  
High Degree

Elevated heat dissipation and simultaneous reductions in package sizes are well documented for a range of electronics systems. The problem is heightened in portable systems where the space available for the implementation of an active cooling methodology is limited and conventional cooling products are too large. Using micro scale radial flow fans is a potential solution. However, little is known about the aerodynamic effects of reducing the fan scale and therefore Reynolds number to the extent required for typical portable electronic applications. This paper investigates this issue, by quantifying the reduction in aerodynamic performance which accompanies the reductions in scale. To do this, geometrically similar radial flow fans were fabricated with diameters ranging from 80 to 10mm. Measurements of the rotors’ geometries are presented, showing a high degree of geometric similarity between the fans. The aerodynamic performance of each of the fans was measured. Non-dimensional performance of each of the larger fans were almost identical, while the performance plot of the smallest fan differed significantly from the others. The paper tentatively concludes that a fundamental change in flow phenomena has emerged in the smallest scale fan which has altered its aerodynamic characteristics.

scholarly journals Numerical investigation of the compressible flow past an aerofoil

2009 ◽  
Vol 643 ◽  
pp. 97-126 ◽  
Author(s):  
LI-WEI CHEN ◽  
CHANG-YUE XU ◽  
XI-YUN LU
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Turbulent Boundary Layer ◽  
Compressible Flow ◽  
Complex Flow ◽  
Dynamical Processes ◽  
Vortical Structures ◽  
Boundary Layer Interaction ◽  
Flow Phenomena ◽  
Flow Evolution

Numerical investigation of the compressible flow past an 18% thick circular-arc aerofoil was carried out using detached-eddy simulation for a free-stream Mach number M∞ = 0.76 and a Reynolds number Re = 1.1 × 107. Results have been validated carefully against experimental data. Various fundamental mechanisms dictating the intricate flow phenomena, including moving shock wave behaviours, turbulent boundary layer characteristics, kinematics of coherent structures and dynamical processes in flow evolution, have been studied systematically. A feedback model is developed to predict the self-sustained shock wave motions repeated alternately along the upper and lower surfaces of the aerofoil, which is a key issue associated with the complex flow phenomena. Based on the moving shock wave characteristics, three typical flow regimes are classified as attached boundary layer, moving shock wave/turbulent boundary layer interaction and intermittent boundary layer separation. The turbulent statistical quantities have been analysed in detail, and different behaviours are found in the three flow regimes. Some quantities, e.g. pressure-dilatation correlation and dilatational dissipation, have exhibited that the compressibility effect is enhanced because of the shock wave/boundary layer interaction. Further, the kinematics of coherent vortical structures and the dynamical processes in flow evolution are analysed. The speed of downstream-propagating pressure waves in the separated boundary layer is consistent with the convection speed of the coherent vortical structures. The multi-layer structures of the separated shear layer and the moving shock wave are reasonably captured using the instantaneous Lamb vector divergence and curl, and the underlying dynamical processes are clarified. In addition, the proper orthogonal decomposition analysis of the fluctuating pressure field illustrates that the dominated modes are associated with the moving shock waves and the separated shear layers in the trailing-edge region. The results obtained in this study provide physical insight into the understanding of the mechanisms relevant to this complex flow.

Compressible Flow Simulations Over Basic Reusable Rocket Configurations

2003 ◽  
Author(s):  
Keiichiro Fujimoto ◽  
Kozo Fujii
Keyword(s):  
Shock Wave ◽  
Mach Number ◽  
Compressible Flow ◽  
Simulation Method ◽  
Aerodynamic Characteristics ◽  
Pressure Level ◽  
The Body ◽  
Navier Stokes ◽  
Aerodynamic Coefficients ◽  
Flow Simulations

Compressible flow around the basic reusable rocket configurations are numerically simulated by Navier-Stokes computations. The study started with the simulations of Apollo configuration to validate the simulation method by the comparison of the aerodynamic data with NASA’s experiments, and the capability of CFD estimation are discussed. Computed aerodynamic coefficients for the Apollo agreed well with the experiments at subsonic to supersonic flow regime for whole angle of attack range. Then, the effects of the configuration parameters on the aerodynamic characteristics are numerically investigated and clarified in detail. It turns out that the aerodynamic characteristicsismainlyinfluenced by the separating position of the flow, shock wave on the surface and the pressure level behind the body. Large shoulder radius causes the strong Mach number dependency of the aerodynamic characteristics, and large fineness ratio strongly influences to the (CL)max.

Aerodynamic Characteristics of Unguided Artillery Projectile

2014 ◽  
Vol 1014 ◽  
pp. 165-168
Author(s):  
Mahfouz Elnaggar Wessam ◽  
Zhi Hua Chen
Keyword(s):  
Compressible Flow ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Coefficients ◽  
Flow Parameters ◽  
Computational Code ◽  
Artillery Projectile

The paper presents results of investigation of a flow over unguided artillery projectile in order to understand variation of flow parameters past a 155 mm artillery projectile M107 and the performance of the computational code. Furthermore; static aerodynamic coefficients were calculated. The flow around projectile was solved as 3-D unsteady compressible flow.

scholarly journals Numerical Analysis of Aerodynamic Characteristics of Hyperloop System

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 518 ◽  
Author(s):  
Jae-Sung Oh ◽  
Taehak Kang ◽  
Seokgyun Ham ◽  
Kwan-Sup Lee ◽  
Yong-Jun Jang ◽  
...  
Keyword(s):  
Mach Number ◽  
Aerodynamic Drag ◽  
Strong Shock ◽  
Aerodynamic Characteristics ◽  
Friction Drag ◽  
Total Drag ◽  
Pressure Drag ◽  
Flow Phenomena ◽  
Pod Length ◽  
Large Parameter Space

The Hyperloop system is a new concept that allows a train to travel through a near-vacuum tunnel at transonic speeds. Aerodynamic drag is one of the most important factors in analyzing such systems. The blockage ratio (BR), pod speed/length, tube pressure, and temperature affect the aerodynamic drag, but the specific relationships between the drag and these parameters have not yet been comprehensively examined. In this study, we investigated the flow phenomena of a Hyperloop system, focusing on the effects of changes in the above parameters. Two-dimensional axisymmetric simulations were performed in a large parameter space covering various BR values (0.25, 0.36), pod lengths (10.75–86 m), pod speeds (50–350 m/s), tube pressures (~100–1000 Pa), and tube temperatures (275–325 K). As BR increased, the pressure drag was significantly affected. This is because of the smaller critical Mach number for a larger BR. As the pod length increased, the total drag and pressure drag did not change significantly, but there was a considerable influence on the friction drag. As the pod speed increased, strong shock waves occurred near the end of the pod. At this point, the flows around the pod were severely choked at both BR values, and the ratio of the pressure drag to the total drag converged to its saturation level. At tube pressures above 500 Pa, the friction drag increased significantly under the rapidly increased turbulence intensity near the pod surface. High tube temperatures increase the speed of sound, and this reduces the Mach number for the same pod speed, consequently delaying the onset of choking and reducing the aerodynamic drag. The results presented in this study are applicable to the fundamental design of the proposed Hyperloop system.

Compressible Flow in Inlet Guide Vanes With Mechanical Flaps

2004 ◽  
Author(s):  
M. Boehle ◽  
M. Cagna ◽  
Lutz Itter
Keyword(s):  
Mach Number ◽  
Compressible Flow ◽  
Classical Type ◽  
Cfd Simulations ◽  
Guide Vanes ◽  
Flow Physics ◽  
Inlet Guide Vanes ◽  
Flow Phenomena ◽  
Analytical Estimation ◽  
Stagger Angle

The classical type of inlet guide vanes consists of uncambered or slightly cambered profiles, the stagger angle of which can be varied. A more advantageous possibility of generating an angular momentum in front of the rotor of the first stage contains the application of inlet guide vanes with mechanical flaps. This configuration consists of uncambered profiles with mechanical flaps. In the present paper, flow physics is explained for this configuration and compared with the flow physics for the classical type of inlet guide vanes. The configuration with mechanical flaps is examined numerically for 20 deg. and 32 deg. flap angles. The emphasis lies on the description of the compressible flow phenomena, which become dominant if the Mach number of the incoming flow gets close to the critical Mach number. An analytical estimation for the Mach number at the exit of the guide vanes is introduced and the results are discussed together with the results of the CFD simulations.

scholarly journals Influence of grid distribution on CFD model of compressible flow inside the primary nozzle and mixing chamber used in refrigeration application

2018 ◽  
Vol 192 ◽  
pp. 02045
Author(s):  
Natthawut Ruangtrakoon ◽  
Eakarach Bumrungthaichaichan
Keyword(s):  
Experimental Data ◽  
Mach Number ◽  
Numerical Methods ◽  
Compressible Flow ◽  
Total Pressure ◽  
Cfd Model ◽  
Regular Grid ◽  
Mixing Chamber ◽  
Flow Phenomena ◽  
Near Wall

In this study, the influence of grid distribution on CFD model of the primary nozzle and mixing chamber used in refrigeration application was primarily investigated. The only one geometry of primary nozzle and mixing chamber was modeled. The two different grid distributions, fine near-wall grid and regular grid with the identical total grid number, were simulated to investigate the flow phenomena inside the considered system. The appropriate boundary conditions and numerical methods were carefully employed. The simulated entrainment ratios obtained by two different grid arrangements were validated by comparing with the reliable experimental data. The results revealed that the Mach number distributions of these models were different. Further, the outlet total pressure predicted by fine near-wall grid was about 1.3% higher than that obtained by regular grid.

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