Physical Analysis of the Three-Dimensional Transition to Turbulence in the Flow Around a Circular Cylinder by Means of Direct Numerical Simulation

1996 ◽  
pp. 375-378
Author(s):  
H. Persillon ◽  
M. Braza
Keyword(s):  
Numerical Simulation ◽  
Circular Cylinder ◽  
Direct Numerical Simulation ◽  
Three Dimensional ◽  
Transition To Turbulence ◽  
Physical Analysis

scholarly journals Direct Numerical Simulation of Flow around a Circular Cylinder Controlled Using Plasma Actuators

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Taichi Igarashi ◽  
Hiroshi Naito ◽  
Koji Fukagata
Keyword(s):  
Numerical Simulation ◽  
Circular Cylinder ◽  
Direct Numerical Simulation ◽  
Drag Reduction ◽  
Three Dimensional ◽  
Reduction Rate ◽  
Plasma Actuators ◽  
Two Dimensional ◽  
Freestream Velocity ◽  
The Mean

Flow around a circular cylinder controlled using plasma actuators is investigated by means of direct numerical simulation (DNS). The Reynolds number based on the freestream velocity and the cylinder diameter is set atReD=1000. The plasma actuators are placed at±90° from the front stagnation point. Two types of forcing, that is, two-dimensional forcing and three-dimensional forcing, are examined and the effects of the forcing amplitude and the arrangement of plasma actuators are studied. The simulation results suggest that the two-dimensional forcing is primarily effective in drag reduction. When the forcing amplitude is higher, the mean drag and the lift fluctuations are suppressed more significantly. In contrast, the three-dimensional forcing is found to be quite effective in reduction of the lift fluctuations too. This is mainly due to a desynchronization of vortex shedding. Although the drag reduction rate of the three-dimensional forcing is slightly lower than that of the two-dimensional forcing, considering the power required for the forcing, the three-dimensional forcing is about twice more efficient.

Three-dimensional direct numerical simulation of infrasound propagation in the Earth’s atmosphere

2018 ◽  
Vol 859 ◽  
pp. 754-789 ◽  
Author(s):  
R. Sabatini ◽  
O. Marsden ◽  
C. Bailly ◽  
O. Gainville
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Stokes Equations ◽  
Fluid Dynamic ◽  
Lower Thermosphere ◽  
Three Dimensional ◽  
Stratified Medium ◽  
Horizontal Wind ◽  
Physical Analysis ◽  
Strong Impact

A direct numerical simulation of the three-dimensional unsteady compressible Navier–Stokes equations is performed to investigate the infrasonic field generated in a realistic atmosphere by an explosive source placed at ground level. To this end, a high-order finite-difference method originally developed for aeroacoustic applications is employed. The maximum overpressure and the main frequency of the signal recorded at 4 km distance from the source location are about 4000 Pa and 0.2 Hz, respectively. The atmosphere is parametrized as a vertically stratified medium, constructed by specifying vertical profiles of the temperature and the horizontal wind which reproduce measurements. The computation is carried out up to 140 km altitude and 450 km range. The goal of the present paper is twofold. On the one hand, the feasibility of using a direct numerical simulation of the three-dimensional fluid dynamic equations for the detailed description of long-range propagation in the atmosphere is proven. On the other hand, a physical analysis of the infrasonic field is realized. In particular, great attention is directed towards some important phenomena which are not taken into account or not well predicted by classical propagation models. To begin with, the present study clearly demonstrates that the weakly nonlinear ray theory may lead to an incorrect evaluation of the waveform distortion of high-amplitude waves propagating towards the lower thermosphere. In addition, signals recorded in the shadow zones are investigated. In this regard, the influence on the acoustic field of temperature and wind inhomogeneities of length scale comparable with the acoustic wavelength is analysed. The role of diffraction at the thermospheric caustic is finally examined and it is pointed out that the amplitude of the source may have a strong impact on the length of the shadow zone.

Direct Numerical Simulation of the Three-Dimensional Transition to Turbulence in the Incompressible Flow around a Wing

2003 ◽  
Vol 71 (1-4) ◽  
pp. 119-132 ◽  
Author(s):  
Y. Hoarau ◽  
D. Faghani ◽  
M. Braza ◽  
R. Perrin ◽  
D. Anne-Archard ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Incompressible Flow ◽  
Three Dimensional ◽  
Transition To Turbulence
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