scholarly journals Transition control in a three-dimensional boundary layer at elevated free stream turbulence using dielectric barrier discharge

2019 ◽  
Vol 486 (6) ◽  
pp. 668-672
Author(s):  
S. A. Baranov ◽  
A. Ph. Kiselev ◽  
I. A. Moralev ◽  
D. S. Sboev ◽  
S. N. Tolkachev ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Dielectric Barrier Discharge ◽  
Free Stream ◽  
Barrier Discharge ◽  
Flow Instability ◽  
Three Dimensional ◽  
Cross Flow ◽  
Dielectric Barrier ◽  
Free Stream Turbulence ◽  
Dimensional Boundary

The results of an experimental study of the effect of dielectric barrier discharge (DBR) actuator on laminar-turbulent transition in a three-dimensional boundary layer under influence of elevated free-stream turbulence are presented. The travelling cross-flow instability modes are dominated in transition in a base configuration. Their characteristics do not depend on a spanwise position. The DBD-actuator that generated stationary cross-flow vortices with the predefined spanwise wavelength when turned on was capable to reduce a turbulent spots production rate in comparison to the base regime.

scholarly journals Conditioning of cross-flow instability modes using dielectric barrier discharge plasma actuators

2017 ◽  
Vol 833 ◽  
pp. 164-205 ◽  
Author(s):  
Jacopo Serpieri ◽  
Srikar Yadala Venkata ◽  
Marios Kotsonis
Keyword(s):  
Boundary Layer ◽  
Discharge Plasma ◽  
Barrier Discharge ◽  
Flow Instability ◽  
Cross Flow ◽  
Plasma Actuators ◽  
Dielectric Barrier Discharge Plasma ◽  
Dielectric Barrier ◽  
Instability Modes ◽  
Barrier Discharge Plasma

In the current study, selective forcing of cross-flow instability modes evolving on a $45^{\circ }$ swept wing at $Re=2.17\times 10^{6}$ is achieved by means of spanwise-modulated plasma actuators, positioned near the leading edge. In the perspective of laminar flow control, the followed methodology holds on the discrete roughness elements/upstream flow deformation (DRE/UFD) approach, thoroughly investigated by e.g. Saric et al. (AIAA Paper 1998-781, 1998), Malik et al. (J. Fluid Mech., vol. 399, 1999, pp. 85–115) and Wassermann & Kloker (J. Fluid Mech., vol. 456, 2002, pp. 49–84). The possibility of using active devices for UFD provides several advantages over passive means, allowing for a wider range of operating $Re$ numbers and pressure distributions. In the present work, customised alternating current dielectric barrier discharge plasma actuators have been designed, manufactured and characterised. The authority of the actuators in forcing monochromatic stationary cross-flow modes at different spanwise wavelengths is assessed by means of infrared thermography. Moreover, quantitative spatio-temporal measurements of the boundary layer velocity field are performed using time-resolved particle image velocimetry. The results reveal distinct steady and unsteady forcing contributions of the plasma actuator on the boundary layer. It is shown that the actuators introduce unsteady fluctuations in the boundary layer, amplifying at frequencies significantly lower than the actuation frequency. In line with the DRE/UFD strategy, forcing a sub-critical stationary mode, with a shorter wavelength compared to the naturally selected mode, results in less amplified primary vortices and related fluctuations, compared to the critical forcing case. The effect of the forcing on the flow stability is further inspected by combining the measured actuators body force with the numerical solution of the laminar boundary layer and linear stability theory. The simplified methodology yields fast and computationally cheap estimates on the effect of steady forcing (magnitude and direction) on the boundary layer stability.

Receptivity mechanisms in three-dimensional boundary-layer flows

2009 ◽  
Vol 618 ◽  
pp. 209-241 ◽  
Author(s):  
LARS-UVE SCHRADER ◽  
LUCA BRANDT ◽  
DAN S. HENNINGSON
Keyword(s):  
Boundary Layer ◽  
Free Stream ◽  
Three Dimensional ◽  
Leading Edge ◽  
Nonlinear Process ◽  
Transition To Turbulence ◽  
Boundary Layer Flows ◽  
Free Stream Turbulence ◽  
Dimensional Boundary ◽  
Layer Flow

Receptivity in three-dimensional boundary-layer flow to localized surface roughness and free-stream vorticity is studied. A boundary layer of Falkner–Skan–Cooke type with favourable pressure gradient is considered to model the flow slightly downstream of a swept-wing leading edge. In this region, stationary and travelling crossflow instability dominates over other instability types. Three scenarios are investigated: the presence of low-amplitude chordwise localized, spanwise periodic roughness elements on the plate, the impingement of a weak vortical free-stream mode on the boundary layer and the combination of both disturbance sources. Three receptivity mechanisms are identified: steady receptivity to roughness, unsteady receptivity to free-stream vorticity and unsteady receptivity to vortical modes scattered at the roughness. Both roughness and vortical modes provide efficient direct receptivity mechanisms for stationary and travelling crossflow instabilities. We find that stationary crossflow modes dominate for free-stream turbulence below a level of about 0.5%, whereas higher turbulence levels will promote the unsteady receptivity mechanism. Under the assumption of small amplitudes of the roughness and the free-stream disturbance, the unsteady receptivity process due to scattering of free-stream vorticity at the roughness has been found to give small initial disturbance amplitudes in comparison to the direct mechanism for free-stream modes. However, in many environments free-stream vorticity and roughness may excite interacting unstable stationary and travelling crossflow waves. This nonlinear process may rapidly lead to large disturbance amplitudes and promote transition to turbulence.

Attenuation of Cross-Flow Instability in a Three-Dimensional Boundary Layer by Means of a Multidischarge Actuator System

2019 ◽  
Vol 64 (9) ◽  
pp. 365-369
Author(s):  
S. A. Baranov ◽  
M. D. Gamirullin ◽  
A. Ph. Kiselev ◽  
A. P. Kuryachii ◽  
D. S. Sboev ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Flow Instability ◽  
Three Dimensional ◽  
Cross Flow ◽  
Dimensional Boundary ◽  
Actuator System

scholarly journals Attenuation of cross-flow instability in three-dimensional boundary layer by means of multi-discharge actuator system

2019 ◽  
Vol 488 (2) ◽  
pp. 147-152
Author(s):  
S. A. Baranov ◽  
M. D. Gamirullin ◽  
A. Ph. Kiselev ◽  
A. P. Kuryachii ◽  
D. S. Sboev ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Body Force ◽  
Flow Instability ◽  
Three Dimensional ◽  
Cross Flow ◽  
The Body ◽  
Subsonic Wind Tunnel ◽  
Significant Area ◽  
Dimensional Boundary ◽  
Force Impact

Results of experiments in low-turbulence subsonic wind tunnel sustaining the possibility of significant attenuation of the cross-flow velocity and the intensity of stationary instability vortices due to the body force impact on three-dimensional boundary layer are presented. The unidirectional body force over a significant area of the streamlined surface has been created with the help of dielectric barrier discharge actuator.

Some observations of the transition process on the windward face of a long yawed cylinder

1985 ◽  
Vol 150 ◽  
pp. 329-356 ◽  
Author(s):  
D. I. A. Poll
Keyword(s):  
Boundary Layer ◽  
Flow Instability ◽  
Three Dimensional ◽  
Cross Flow ◽  
Transition Process ◽  
Theoretical Models ◽  
Boundary Layer Flows ◽  
Sufficient Detail ◽  
Oil Flow ◽  
Dimensional Boundary

An experiment has been performed to determine the effect of yaw upon transition in the boundary layer formed on the windward face of a long cylinder. The china-clay-evaporation and surface-oil-flow techniques have been used to study the development of the fixed-wavelength stationary disturbances which are characteristic of cross-flow instability. It has been found that the boundary layer is also susceptible to time-dependent disturbances which grow to very large amplitudes prior to the onset of transition. These disturbances have been studied with a hot-wire anemometer. The conditions necessary for the onset and completion of transition have been determined by the use of surface Pitot tubes. Data from the experiment have been compared with the simple criteria for instability and transition which were proposed by Owen & Randall over thirty years ago. In general it has been found that these criteria are inadequate, and, where possible, improvements have been proposed. The raw data are presented in sufficient detail for them to be used to test, or calibrate, future theoretical models of the transition process in three-dimensional boundary-layer flows.

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