Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study of flow induced by sine wave and saw tooth plasma actuators

28.11.2011
How to improve the performance of the plasma actuators is a problem that is of great interest to many scientific researchers in the field of electrohydrodynamics.

Professor WANG Lianze and his group from the School of Aerospace, Tsinghua University, set out to investigate this problem. They developed novel plasma actuators using various winding-shaped electrodes to create plasma actuators which induce three-dimensional variations in the shear layer, offering significant flexibility in flow control. Their work, entitled "Study of Flow Induced by Sine Wave and Saw Tooth Plasma Actuators", was published in SCIENCE CHINA Physics, Mechanics & Astronomy.2011, Vol 54(11).


This is the 3-D view of the field induced by the saw tooth actuator (C1) at various z for Urms=10 Kv and frequency=8 KHz. The bold lines indicate the actuator location. Credit: Copyright Science China Press

Studies on flow control devices have focused primarily on adding momentum to the boundary layer or using trips to initiate a transition to leading edge devices. Thus, in general, manipulation of the boundary layer has been the main objective for flow control. To achieve this, certain devices, such as vortex generator jets or zero-net mass flux (ZNMF) synthetic jets and plasma actuators in various configurations have been used for flow control or thrust generation.

Plasma actuators, also known as dielectric barrier discharge (DBD) or devices, have been used as active flow control devices and received increasing interest in the past decade. Typically, a widely used type of plasma actuator [single DBD (SDBD)] refers to an asymmetric arrangement of two horizontally offset electrodes separated by a dielectric material. Under a high enough voltage input and a high-frequency AC or a pulsed DC signal, a region of weakly ionized air (plasma) is created over the covered electrode (typically less than one part per million of weakly ionized gas). The plasma appears blue and can be viewed easily with the naked eye in a darkened environment. In the presence of an electric field produced by high voltages between the electrodes, the electric field exceeds (the value needed to sustain electron–ion pairs in gas in the absence of space charge fields). The air is ionized, resulting in a body-force vector field that acts on the ambient (non-ionized and neutrally charged) air and, thus, inducing a ZNMF jet. This is the mechanism for active aerodynamic control. For conventional linear plasma actuator, the mechanism of the flow control is through a generated body-force vector field that couples with the momentum in the external flow. Previous researchers have made possible the exertion of significant electrohydrodymanic body forces in the boundary layer above the electrodes on aerodynamic surfaces, and the plasma actuators have been shown to control flow separation by adding near-wall flow momentum in low Re flow environments.

However, practical flow control applications demand robust actuators that have sufficient capability for operation in the Re and Mach number regimes, and thus, improvement of their control effect is highly sought after. Previous studies were conducted in the field of plasma actuator improvement to examine various aspects, such as the effects of dielectric material and thickness, voltage amplitude and frequency, voltage waveform, exposed electrode geometry, and the number of actuators in series.

Some studies have shown that the control effect of a plasma actuator is relatively strong in low Re and not very effective in high Re number regimes for various reasons, including inefficient energy transformation due to heat emission from the insulation board. However, some important aspects may have been neglected. The key point of these studies lies in the improvement of the tangential velocity or electric energy of the actuator. Thus, focusing on another aspect aimed at making appropriate changes to the actuator that extend the traditional two-dimensional (2-D) flow field to a three-dimensional (3-D) flow field, such as the introduction of streamwise vortex flow (traditional actuator can induce spanwise vortex flow), would result in a better energy mix and generate a stronger control effect. With the goal of improving actuator capability for applications in higher Re flows than previously possible, novel designs that use various electrode shapes (sawtooth and sine wave) were investigated in this study. These designs adjusted the plasma induced flow in the form of a ZNMF jet with streamwise and spanwise vortices, as shown in Fig. 1. These new designs render the plasma-induced flow in the form of streamwise and spanwise vortices upon actuation. These new DBD plasma actuators have the enhanced ability to induce a streamwise vortex and, at the same time, possess the advantages of the original linear actuator.

See the article: LIU Zhifeng, WANG Lianze, FU Song. Study of Flow Induced by Sine Wave and Saw Tooth Plasma Actuators. SCIENCE CHINA Physics, Mechanics & Astronomy.2011, Vol 54(11): 2033-2039.

LIU Zhifeng | EurekAlert!
Further information:
http://www.tsinghua.edu.cn

More articles from Studies and Analyses:

nachricht New study: How does Europe become a leading player for software and IT services?
03.04.2017 | Fraunhofer-Institut für System- und Innovationsforschung (ISI)

nachricht Reusable carbon nanotubes could be the water filter of the future, says RIT study
30.03.2017 | Rochester Institute of Technology

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

Physicists discover mechanism behind granular capillary effect

24.05.2017 | Physics and Astronomy

Measured for the first time: Direction of light waves changed by quantum effect

24.05.2017 | Physics and Astronomy

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>