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1 – 10 of 31Nima Vaziri, Ming-Jyh Chern, Tzyy-Leng Horng and Syamsuri Syamsuri
The purpose of this study is to the modeling of the dielectric barrier discharge (DBD) actuator on the Eppler 387 (E387) airfoil in low Reynolds number conditions.
Abstract
Purpose
The purpose of this study is to the modeling of the dielectric barrier discharge (DBD) actuator on the Eppler 387 (E387) airfoil in low Reynolds number conditions.
Design/methodology/approach
A validated direct-forcing immersed boundary method is used to solve the governing equations. A linear electric field model is used to simulate the DBD actuator. A ray-casting technique is used to define the geometry.
Findings
The purposed model is validated against the former studies. Next, the drag and lift coefficients in the static stall of the E387 airfoil are investigated. Results show that when the DBD actuator is on, both of the coefficients are increased. The effects of the location, applied voltage and applied frequency are also studied and find that the leading-edge actuator with higher voltage and frequency has better improvement in the forces. Finally, the dynamic stall of the E387 with the DBD actuator is considered. The simulation shows that generally when the DBD is on, the lift coefficient in the pitch-up section has lower values and in the pitch-down has higher values than the DBD off mode.
Practical implications
It is demonstrated that using the DBD actuator on E387 in the low Reynolds number condition can increase the lift and drag forces. Therefore, the application of the airfoil must be considered.
Originality/value
The results show that sometimes the DBD actuator has different effects on E387 airfoil in low Reynolds number mode than the general understanding of this tool.
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Junjie Niu, Weimin Sang, Feng Zhou and Dong Li
This paper aims to investigate the anti-icing performance of the nanosecond dielectric barrier discharge (NSDBD) plasma actuator.
Abstract
Purpose
This paper aims to investigate the anti-icing performance of the nanosecond dielectric barrier discharge (NSDBD) plasma actuator.
Design/methodology/approach
With the Lagrangian approach and the Messinger model, two different ice shapes known as rime and glaze icing are predicted. The air heating in the boundary layer over a flat plate has been simulated using a phenomenological model of the NSDBD plasma. The NSDBD plasma actuators are planted in the leading edge anti-icing area of NACA0012 airfoil. Combining the unsteady Reynolds-averaged Navier–Stokes equations and the phenomenological model, the flow field around the airfoil is simulated and the effects of the peak voltage, the pulse repetition frequency and the direction arrangement of the NSDBD on anti-icing performance are numerically investigated, respectively.
Findings
The agreement between the numerical results and the experimental data indicates that the present method is accurate. The results show that there is hot air covering the anti-icing area. The increase of the peak voltage and pulse frequency improves the anti-icing performance, and the direction arrangement of NSDBD also influences the anti-icing performance.
Originality/value
A numerical strategy is developed combining the icing algorithm with the phenomenological model. The effects of three parameters of NSDBD on anti-icing performance are discussed. The predicted results show that the anti-icing method is effective and may be helpful for the design of the anti-icing system of the unmanned aerial vehicle.
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David S. Martínez, Elisa Pescini, Maria Grazia De Giorgi and Antonio Ficarella
Reynolds number in small-size low-pressure turbines (LPT) can drop below 2.5 · 104 at high altitude cruise, which in turn can lead to laminar boundary layer separation on the…
Abstract
Purpose
Reynolds number in small-size low-pressure turbines (LPT) can drop below 2.5 · 104 at high altitude cruise, which in turn can lead to laminar boundary layer separation on the suction surface of the blades. The purpose of this paper is to investigate the potential of an alternate current (AC)-driven Single Dielectric Barrier Discharge Plasma Actuator (AC-SDBDPA) for boundary layer control on the suction side of a LPT blade, operating at a Reynolds number of 2 · 104.
Design/methodology/approach
Experimental and numerical analyses were conducted. The experimental approach comprised the actuator testing over a curved plate with a shape designed to reproduce the suction surface of a LPT blade. A closed loop wind tunnel was employed. Sinusoidal voltage excitation was tested. Planar velocity measurements were performed by laser Doppler velocimetry (LDV) and particle image velocimetry (PIV). The device electrical power dissipation was also calculated. Computational fluid dynamics (CFD) simulations using OpenFOAM© were conducted, modelling the actuator effect as a body force calculated by the dual potential algebraic model. Unsteady RANS (Reynolds Averaged Navier-Stokes equations), also known as URANS approach, with the k-ε Lam-Bremhorst Low-Reynolds turbulence model was used.
Findings
The AC-SDBDPA operation brought to a reduction of the separation region; in particular, the boundary layer thickness and the negative velocity values decreased substantially. Moreover, the flow angle in both the main flow and in the boundary layer was reduced by the plasma control effect. The actuation brought to a reduction of the 17 per cent in the total pressure loss coefficient. The pressure coefficient and skin friction coefficient distributions indicated that under actuation the reattacnment point was displaced upstream, meaning that the flow separation was effectively controlled by the plasma actuation. Adopting slightly higher actuation parameters could bring to a full reattachment of the flow.
Practical implications
The work underlines the potentialities of an AC-SDBDPA to control separation in LPTs of aeroengines.
Originality/value
The present work sets a methodological framework, in which the validated procedure to obtain the body force model combined with CFD simulations can be used to study a configuration with multiple actuators allocated in array without requiring further experiments.
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Martin Skote and Imran Halimi Ibrahim
The cylindrical wake flow is an important part of many engineering applications, including wake turbulence, acoustic noise, and lift/drag forces on bodies. The suppression of von…
Abstract
Purpose
The cylindrical wake flow is an important part of many engineering applications, including wake turbulence, acoustic noise, and lift/drag forces on bodies. The suppression of von Kármán vortex street (VKS) is an important goal for flow control devices. The paper aims to discuss these issues.
Design/methodology/approach
The linear plasma synthetic jet actuator (L-PSJA) is utilized as a flow control device to suppress the VKS formation. Different configurations of the device is studied numerically.
Findings
Of the 12 configurations that were investigated, five configurations were able to suppress the formation of the VKS.
Originality/value
For the first time, the L-PSJA has been shown (through numerical simulations) to be able to suppress VKS.
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Burak Karadag, Cem Kolbakir and Ahmet Selim Durna
This paper aims to investigate the effects of a dielectric barrier discharge (DBD) plasma actuator (PA) qualitatively on aerodynamic characteristics of a 3 D-printed NACA 4412…
Abstract
Purpose
This paper aims to investigate the effects of a dielectric barrier discharge (DBD) plasma actuator (PA) qualitatively on aerodynamic characteristics of a 3 D-printed NACA 4412 airfoil model.
Design/methodology/approach
Airflow visualization study was performed at a Reynolds number of 35,000 in a small-scale open-loop wind tunnel. The effect of plasma actuation on flow separation was compared for the DBD PA with four different electrode configurations at 10°, 20° and 30° angles of attack.
Findings
Plasma activation may delay the onset of flow separation up to 6° and decreases the boundary layer thickness. The effects of plasma diminish as the angle of attack increases. Streamwise electrode configuration, in which electric wind is produced in a direction perpendicular to the freestream, is more effective in the reattachment of the airflow compared to the spanwise electrode configuration, in which the electric wind and the free stream are in the same direction.
Practical implications
The Reynolds number is much smaller than that in cruise aircraft conditions; however, the results are promising for low-velocity subsonic airflows such as improving control capabilities of unmanned aerial vehicles.
Originality/value
Superior efficacy of spanwise-generated electric wind over streamwise-generated one is demonstrated at a very low Reynolds number. The results in the plasma aerodynamics literature can be reproduced using ultra-low-cost off-the-shelf components. This is important because high voltage power amplifiers that are frequently encountered in the literature may be prohibitively expensive especially for resource-limited university aerodynamics laboratories.
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Imran Halimi Bin Ibrahim and Martin Skote
For the past decade, plasma actuators have been identified as a subset in the realm of active flow control devices. As research into plasma actuators continues to mature…
Abstract
Purpose
For the past decade, plasma actuators have been identified as a subset in the realm of active flow control devices. As research into plasma actuators continues to mature, computational modelling is needed to complement the investigation of the actuators. This paper seeks to address these issues.
Design/methodology/approach
In this study, the Suzen‐Huang model is chosen because of its ability to simulate both the charge density and Lorentz body force. Its advantages and limitations have been identified with a parametric study of two constants used in the modelling: the Debye length (λD) and the maximum charge density value (ρc* ). By varying the two scalars, the effects of charge density, body force and induced velocity are examined.
Findings
The results show that the non‐dimensionalised body force (Fb*) is nonlinearly dependent on Debye length. However, a linear variation of Fb* is observed with increasing values of maximum charge density. The optimized form of the Suzen‐Huang model shows better agreement in the horizontal velocity profile but still points to inaccuracy when compared to vertical velocity profile.
Originality/value
The results indicate that the body force still has to be modelled more extensively above the encapsulated electrode, so that the horizontal and vertical components of induced velocities are accurately obtained.
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Abbas Ebrahimi, Majid Hajipour and Kamran Ghamkhar
The purpose of this paper is to control flow separation over a NACA 4415 airfoil by applying unsteady forces to the separated shear layers using dielectric barrier discharge (DBD…
Abstract
Purpose
The purpose of this paper is to control flow separation over a NACA 4415 airfoil by applying unsteady forces to the separated shear layers using dielectric barrier discharge (DBD) plasma actuators. This novel flow control method is studied under conditions which the airfoil angle of attack is 18°, and Reynolds number based on chord length is 5.5 × 105.
Design/methodology/approach
Large eddy simulation of the turbulent flow is used to capture vortical structures through the airfoil wake. Power spectral density analysis of the baseline flow indicates dominant natural frequencies associated with “shear layer mode” and “wake mode.” The wake mode frequency is used simultaneously to excite separated shear layers at both the upper surface and the trailing edge of the airfoil (dual-position excitation), and it is also used singly to excite the upper surface shear layer (single-position excitation).
Findings
Based on the results, actuations manipulate the shear layers instabilities and change the wake patterns considerably. It is revealed that in the single-position excitation case, the vortices shed from the upper surface shear layer are more coherent than the dual-position excitation case. The maximum value of lift coefficient and lift-to-drag ratio is achieved, respectively, by single-position excitation as well as dual-position excitation.
Originality/value
The paper contributes to the understanding and progress of DBD plasma actuators for flow control applications. Further, this research could be a beneficial solution for the promising design of advanced low speed flying vehicles.
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Alireza Ghayour and Mahmoud Mani
The purpose of this paper is to compare the effects of two different configurations of plasma streamwise vortex generators (PSVG), including comb-type and mesh-type in controlling…
Abstract
Purpose
The purpose of this paper is to compare the effects of two different configurations of plasma streamwise vortex generators (PSVG), including comb-type and mesh-type in controlling flow. This is demonstrated on the NACA 0012 airfoil.
Design/methodology/approach
The investigations have been done experimentally at the various electric and aerodynamic conditions. The surface oil flow visualization method has been used to the better understanding of the flow physics and the interaction of the oncoming flow passing over the airfoil and the vortex generated by comb-type PSVG.
Findings
This paper demonstrates the potential capabilities of the mesh-type and comb-type PSVGs in controlling flow in unsteady operation. It was found that the vortex generated by the mesh-type PSVG in unsteady operation was an order of magnitude stronger than comb-type PSVG. The flow visualisation technic proved that only a part of the plasma actuator is effective in the condition that the actuator is installed only on a portion of the upper surface of the airfoil.
Originality/value
This paper experimentally confirms the capabilities of the mesh-type PSVG unsteady operation in compare with comb-type PSVG in controlling flow, whereby recommends using mesh-type PSVG in the leading edge in front of comb-type PSVG on the entire wingspan to prevent the stall.
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Xingquan Wang, Xiuyuan Lu, Wei Chen, Fengpeng Wang, Jun Huang, Lingli Liu, Mengchao Li and Kui Lin
This paper aims to improve the general circuit of driving and protection based on insulated gate bipolar transistor (IGBT) in dielectric barrier discharge power supply by…
Abstract
Purpose
This paper aims to improve the general circuit of driving and protection based on insulated gate bipolar transistor (IGBT) in dielectric barrier discharge power supply by designing a novel half-bridge inverter circuit with discrete components.
Design/methodology/approach
With one SG3524 chip, the structure based on discrete components is used to design the IGBT drive circuit. The driving waveform is isolated and sent out by photo-coupler 6N137. The protection circuit is realized by Hall sensor directly detecting the main circuit current, supplemented by a few components, including diodes, resistors, capacitors and triodes. It improves the reliability of the protection circuit.
Findings
In the driving circuit, the phase difference of signals from two channels are 180°. Moreover, when the duty cycle is set at 40%, it can ensure sufficient pulse width modulation response time. In the protection circuit, when over-current occurs, an intermittent output signal is automatically sent out. Furthermore, the over-current response time can be controlled independently. The peak voltage can be adjusted continuously from 0 to 30 kV with its frequency from 8 to 25 kHz and the power output up to 150 W.
Originality/value
The novel circuit of driving and protection makes not only its structure simpler and easier to be realized but also key parameters, such as frequency, the duty cycle and the driving voltage, continuously adjustable. Moreover, the power supply is suitable for other discharges such as corona discharge and jet discharge.
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This paper gives a bibliographical review of the finite element methods (FEMs) applied to the analysis of ceramics and glass materials. The bibliography at the end of the paper…
Abstract
This paper gives a bibliographical review of the finite element methods (FEMs) applied to the analysis of ceramics and glass materials. The bibliography at the end of the paper contains references to papers, conference proceedings and theses/dissertations on the subject that were published between 1977‐1998. The following topics are included: ceramics – material and mechanical properties in general, ceramic coatings and joining problems, ceramic composites, ferrites, piezoceramics, ceramic tools and machining, material processing simulations, fracture mechanics and damage, applications of ceramic/composites in engineering; glass – material and mechanical properties in general, glass fiber composites, material processing simulations, fracture mechanics and damage, and applications of glasses in engineering.
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