Compressible Flow Phenomena at Inception of Lateral Density Currents Fed by Collapsing Gas-Particle Mixtures

2018 ◽  
Vol 123 (2) ◽  
pp. 1286-1302 ◽  
Author(s):  
Greg A. Valentine ◽  
Matthew R. Sweeney
Keyword(s):  
Compressible Flow ◽  
Density Currents ◽  
Flow Phenomena

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.

Simulating the frontal instability of lock-exchange density currents with dissipative particle dynamics

2016 ◽  
Vol 30 (17) ◽  
pp. 1650200 ◽  
Author(s):  
Yanggui Li ◽  
Xingguo Geng ◽  
Heping Wang ◽  
Xin Zhuang ◽  
Jie Ouyang
Keyword(s):  
Dissipative Particle Dynamics ◽  
Particle Dynamics ◽  
Small Scale ◽  
Density Currents ◽  
Two Phase ◽  
Flow Phenomena ◽  
Particle Level ◽  
Macroscopic Simulation ◽  
Frontal Instability ◽  
Dpd Simulation

The frontal instability of lock-exchange density currents is numerically investigated using dissipative particle dynamics (DPD) at the mesoscopic particle level. For modeling two-phase flow, the “color” repulsion model is adopted to describe binary fluids according to Rothman–Keller method. The present DPD simulation can reproduce the flow phenomena of lock-exchange density currents, including the lobe-and-cleft instability that appears at the head, as well as the formation of coherent billow structures at the interface behind the head due to the growth of Kelvin–Helmholtz instability. Furthermore, through the DPD simulation, some small-scale characteristics can be observed, which are difficult to be captured in macroscopic simulation and experiment.

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

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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