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.

scholarly journals Modelling of the processes of impact of a projectile with elements of individual defence

2019 ◽  
Vol 221 ◽  
pp. 01021
Author(s):  
Aleksandr Kraus ◽  
Evgeny Kraus ◽  
Ivan Shabalin
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Heterogeneous Media ◽  
Three Dimensional ◽  
Stationary Problem ◽  
Heterogeneous Structure ◽  
Plate Steel ◽  
Two Dimensional ◽  
Human Bones ◽  
Armor Plate

A two-dimensional and three-dimensional non-stationary problem of the interaction of a homogeneous impactor and a heterogeneous structure made of steel and ceramics and placed in a Kevlar pocket is considered. The model of the human body is a plate of gelatine with cylindrical inserts-imitators of human bones. The results of numerical simulation using different approaches for describing heterogeneous media are compared. On the basis of direct numerical simulation, it is shown that the gradient armor plate (steel + B4C) has the best weight and size parameters.

Small-scale structure of two-dimensional magnetohydrodynamic turbulence

1979 ◽  
Vol 90 (1) ◽  
pp. 129-143 ◽  
Author(s):  
Steven A. Orszag ◽  
Cha-Mei Tang
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Three Dimensional ◽  
Scale Structure ◽  
Magnetohydrodynamic Flow ◽  
Small Scale ◽  
Two Dimensional ◽  
Magnetohydrodynamic Turbulence ◽  
Hydrodynamic Turbulence ◽  
Small Scale Structure

The formation of singularities in two-dimensional magnetohydrodynamic flow is investigated by direct numerical simulation. It is shown that two-dimensional magnetohydrodynamic turbulence is not as singular as three-dimensional hydrodynamic turbulence (in the sense that it has a less highly excited small-scale structure) but that it is more singular than two-dimensional hydrodynamic turbulence.

Direct numerical simulation of forced MHD turbulence at low magnetic Reynolds number

1998 ◽  
Vol 358 ◽  
pp. 299-333 ◽  
Author(s):  
OLEG ZIKANOV ◽  
ANDRE THESS
Keyword(s):  
Magnetic Field ◽  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Boundary Conditions ◽  
Interaction Parameter ◽  
Three Dimensional ◽  
Magnetic Interaction ◽  
Two Dimensional ◽  
Mhd Turbulence ◽  
Magnetic Interaction Parameter

The transformation of initially isotropic turbulent flow of electrically conducting incompressible viscous fluid under the influence of an imposed homogeneous magnetic field is investigated using direct numerical simulation. Under the assumption of large kinetic and small magnetic Reynolds numbers (magnetic Prandtl number Pm[Lt ]1) the quasi-static approximation is applied for the computation of the magnetic field fluctuations. The flow is assumed to be homogeneous and contained in a three-dimensional cubic box with periodic boundary conditions. Large-scale forcing is applied to maintain a statistically steady level of the flow energy. It is found that the pathway traversed by the flow transformation depends decisively on the magnetic interaction parameter (Stuart number). If the magnetic interaction number is small the flow remains three-dimensional and turbulent and no detectable deviation from isotropy is observed. In the case of a strong magnetic field (large magnetic interaction parameter) a rapid transformation to a purely two-dimensional steady state is obtained in agreement with earlier analytical and numerical results for decaying MHD turbulence. At intermediate values of the magnetic interaction parameter the system exhibits intermittent behaviour, characterized by organized quasi-two-dimensional evolution lasting several eddy-turnover times, which is interrupted by strong three-dimensional turbulent bursts. This result implies that the conventional picture of steady angular energy transfer in MHD turbulence must be refined. The spatial structure of the steady two-dimensional final flow obtained in the case of large magnetic interaction parameter is examined. It is found that due to the type of forcing and boundary conditions applied, this state always occurs in the form of a square periodic lattice of alternating vortices occupying the largest possible scale. The stability of this flow to three-dimensional perturbations is analysed using the energy stability method.

Direct Numerical Simulation of Turbulent Friction Drag Reduction by Traveling Wave-Like Blowing Using Plasma Actuators

2011 ◽  
Author(s):  
Yasuhito Murai ◽  
Koji Fukagata
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Drag Reduction ◽  
Traveling Wave ◽  
Body Force ◽  
Phase Speed ◽  
The Body ◽  
Plasma Actuators ◽  
Friction Drag ◽  
Friction Drag Reduction

We numerically investigated the effects of friction drag reduction and energy gain by traveling wave-like blowing using plasma actuators arrayed on channel walls. Wall-normal flow is induced by opposed arrangement of plasma actuators. We used Shyy et al.’s model [1] to compute the body force of plasma actuators, which is added to the Navier-Stokes equation. With this model, the body force distribution is simplified as compared to the actual one, which is quite complicated. We perform direct numerical simulation under several parameter sets: the wavenumber, the amplitude, and the phasespeed of body forces. The obtained maximum friction drag reduction rate is 37% as compared to the uncontrolled case. Under the same phase speed and amplitude of body force, the friction drag is found to be reduced more with larger wavenumber. Under the same phase speed and wavenumber, the friction drag reduction is found to be larger with stronger body force. In the drag reducing cases, formation of spanwise vortices leads to reduction of the Reynolds sheer stress near the wall as well as the friction drag. Although net energy saving is acheived in some parameter sets, it is not achieved in most cases. This means that the reduced pumping power is generally smaller than the power input of plasma actuators.

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