thThe 19 International Symposium on Applied Electromagnetics and Mechanics

C13

Aerodynamic drag reduction using a coating material in flapping wing
Tadateru ISHIDE1, Yasuaki TAKAGI1, Sakishi OTSUBO1, Tomoharu KAERIYAMA1 , Koji SHIMOYAMA2, Shigeru OBAYASHI2(1 National Institute of Technology, Kisarazu College, 2Institute of Fluid Science, Tohoku University)

Motive argument of our technical support
Glass coating agent

PIV Measurement System

coating position
PC including
PCI-compliant
Counter board(1)

Cylindrical Lens

Rotary Encoder Signal

Wind Tunnel(2)Interface Circuit(3)

Fog Generator
Detection Signal of theSpecific Flapping Angle

Table.1 Chemical composition of the coating materials used (mass%)

type

HardoLass O
HardoLass 9
HardoLass A

composition1
composition2polysilazane compound(90%)
polysilazane compound(40%)
Perhydropolysilazane dibutyl ether
(3%)
(53%)

Function
Generator
golf club (1)Pulse Wave of 100ns

Laser Light Sheet

Oil Mist Generator

carrygolf club (2)run

TTL INgolf club (3)PIV Camera

yds

As a result of applying water-shedding coating to the golf club experimentally, as theflying distance measurement, we judged that there was a possibility of the drag reduction.

PC for thePIV Analysis

Synchronizer

Mirror

Double Pulse
Laser

Fig.2 Schematic view of the PIV system

Our Research Motivation
1. Enhance the aerodynamic characteristics of the flapping wing depending on a watershedding coating material consisting primary of SiO2.
2. Clarify the optimum chemical composition in the coating material and theapplication thickness.
3. Investigate the relation between the separated vortex behaviors and thesurface structure near the upper surface of the wing.

We have developed a synchronization system of laser irradiation and flapping angle to perform the PIV
measurements for the leading edge vortex to investigate quantitatively the effect of flapping motion in detail.
1. By counting the signals of the rotary encoder, the specific flapping angle is detected.
2. At the same time as the detection, the digital signal is output to the TTL IN terminal of the function
generator.
3. Double Pulse Nd:YAG Laser is irradiated by a pulse wave from the synchronizer of external mode withabove TTL signal of 100 ns as a trigger.
By injecting tracer of two kinds(Glycol and Olive Oil), we succeeded in obtaining a clearer visualized image.

Measurements of Fluid Forces
Get a new insight on aerodynamical effect of the coating material for air flow.

Table.4 Experimental conditions
Uniform flow
velocity U

Experimental Apparatus

7 m/s

Angle of attack α 0º～30º, Δα=2ºFlapping
frequency f0(fixed),7Hz

Flapping
amplitude FA0º(fixed) ,20º

Data sampling
frequency

1 kHz

Data samplingtime t・Flapping Amplitude
0 degrees to 60 degrees
・Flapping Frequency 0Hz to 10Hz
・Rotary Encoder for detect a Flapping Angle

Fig.3 Lift curves20sec

At this time, five kinds of coating conditions
have been tested regarding fluid force
measurement.

From the figure of drag curves, the effectof coating material is not identified.

Specification of the Elliptical Wing
Modeling
Table.2 Specifications of the Elliptical Wings
Vero White Plus
Material(RGD835)
Chord Length
60mm
Aspect Ratio AR
8Thickness
1.5mm
Table.3 Coating film thickness
Coatingmethod
Brushing
material
Rapid prototyping

Coating filmThickness①②Fig.4 Drag curves③

both ofmelamine brushing microfiber
sponge materials
cloth① and ③2~3µm

1µmFig.4 Lift drug ratio

Fig.5 Lift-drag ratio curves
The CD value of any other coatingconditions are less than uncoated one.
The CD value of HardoLass O① is lessby 13.5% than uncoated one at attack
angle α=20º.

The CL /CD value of HardoLass 9② islarge in the angle of attack range from4º to 8º.

～0.1µmConcluding Remarks
There are kinds of coating method dependingon brushing material such as melamine
sponge and microfiber cloth.

(1) The coating material reduces a drag under appropriate coating method.
(2) The relation between the drag reduction effect and fluid phenomena will be considereddepending on high accurate PIV measurement.

Fig.1 Elliptical wingThree dimensional printer is used for manufacturing the above mentioned wings.
The type of this printer is Poly-jet. In this method, a resin of which laminating
pitch is 28μm is sprayed to the build tray.

Acknowledgements
Part of the work was carried out under the Collaborative Research Project of the Institute of Fluid
Science, Tohoku University.