Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Variable camber airfoil: New concept, new challenge

20.06.2012
Aircraft morphing, especially in the case of the variable camber airfoil, has potential from the viewpoints of both fundamental aerodynamics and flight application.

In the field of aerodynamics, the use of a variable camber airfoil can improve aircraft flight performance and allow efficient multiple missions; in biology, the concept of the variable camber airfoil can be employed to explain the mystery of animal flight.


This image shows the construction of a variable camber airfoil and a real model. Credit: © Science China Press

In the case of low-speed aircraft, the performance of low-Reynolds-number airfoils is greatly determined by the relatively feeble separation resistance of the laminar boundary layer. Better understanding and effective control of laminar separation is therefore valuable for improving the flight mechanics of low-Reynolds-number aircraft such as micro air vehicles (MAVs). Recent research has demonstrated that the variable camber airfoil has obvious advantages in terms of the control of separation and flight maneuverability.

Furthermore, compliant deformation of the airfoil helps explain the nature of the aerodynamic characteristics of a membrane wing such as that of a bat. However, little attention has been paid to the quasi-steady aerodynamic characteristics resulting from the camber deformation and the effect of different initial flow conditions.

Professor Yang Jiming and his group at the University of Science and Technology of China set out to explore this area of research. Through aerodynamic load measurements and related flow visualization, they distinguished the aerodynamic characteristics of the variable camber airfoil for steady and quasi-steady flow separation behaviors. Their work, entitled "Experimental investigation on the quasi-steady flow separation behaviors of a variable camber wing", was published in SCIENTIA SINICA Physica, Mechanica & Astronomica, 2012, Vol. 42(4).

The group firstly designed a type of variable camber airfoil test model whose camber can be changed smoothly. The baseline airfoil is assumed to have an NACA 0015 profile. A rigid D-spar, the primary load carrying member, extends from the leading edge of the airfoil to the 30-percent chord. The D-spar does not undergo any deformation in the chordwise direction, and consequently, only the section aft of the D-spar can deform. This section aft of the spar is specially designed to have an internal substructure. The substructure comprises five rows of hinge-like units ranked serially along the chordwise direction.

The substructure is designed to support a flexible skin that provides the aerodynamic shape and is capable of morphing. A servomotor was fixed in the D-spar to provide power to pull the lower surface of the aft section into the D-spar to a certain extent with the help of gearing. As part of the lower surface is pulled into the D-spar, there is a discrepancy in the area between the upper surface and lower surface and the airfoil is thus asymmetric; in other words, the airfoil has some camber. The D-spar was made with acrylic materials and the skin of the aft section was made with polypropylene plastics.

Aerodynamic load measurements and a flow visualization technique such as particle image velocimetry are combined to reveal the aerodynamic characteristics resulting from the camber deformation and corresponding flow structures, from which the complex mechanism is hopefully determined. Research shows that on the occasion of flow separation, different camber deformation paths have totally distinct aerodynamic characteristics. Professor Yang's group found that the stall type determines the distinction. For some camber deformation paths, the stall is a type of leading-edge stall.

During this stall process, flow separates rather suddenly and abruptly over the entire top surface of the airfoil, with the origin of this separation being at the leading edge. Therefore, the lift of the airfoil is rather low under the circumstances of large camber. However, for other camber deformation paths, the stall is a type of trailing-edge stall. For this type of stall, there is progressive and gradual movement of separation from the trailing edge toward the leading edge as the camber is increased. Because of this, the trailing-edge stall is "soft" compared with the leading-edge stall and the lift is higher under the same conditions.

Therefore, under flow-separation circumstances, the flow around the airfoil is related not only to the current environment but also to the previous flow characteristics, and the history of flow evolvement should thus be considered in the design of low-Reynolds-number aircraft. The role of the history of flow evolvement tends to be overlooked in traditional aircraft design. Designers often only focus on the steady aerodynamic characteristics of an aircraft. However, to further improve the flight performance of MAVs, engineers will have to face this new challenge.

See the article: Yang W C, Yang J T, Wang J, et al. Experimental investigation on the quasi-steady flow separation behaviors of a variable camber wing. SCIENTIA SINICA Physica, Mechanica & Astronomica. 2012, Vol. 42(4).

Yang Jiming | EurekAlert!
Further information:
http://www.ustc.edu.cn.cn
http://zh.scichina.com/english/

More articles from Machine Engineering:

nachricht Satellite-based Laser Measurement Technology against Climate Change
17.01.2017 | Fraunhofer-Institut für Lasertechnik ILT

nachricht LZH optimizes laser-based CFRP reworking for the aircraft industry
24.11.2016 | Laser Zentrum Hannover e.V.

All articles from Machine Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>