The Application of Fluttering Thin-flat Plates for Wind Harvesting

using Electromagnetic Converter

I P. G. Sopan Rahtika

, I Made Suarta

and I Komang Rusmariadi

Department of Mechanical Engineering, Bali State Polytechic, Badung, Bali, Indonesia

Keywords: Flutter, Wind Harvesting, Thin-flat Plates, Electromagnetic Converter.

Abstract: In this study, a new energy conversion device was designed to convert the energy harvested by fluttering thin–

flat plates into electrical energy. This design uses an electrognetic converter in the form of a magnetically

induced ferromagnetic thin-flat plate to induce electromotive force in a solenoid. The purpose of this study

was to determine the effect of the size of the thin-flat plates on the electromotive force generated by the wind

harvester. Several wind harvesters with various sizes of thin-flat plates were placed in a subsonic wind tunnel

for testing. The test included measuring the energy produced by the wind havester in the form of the generated

electrical voltage.

1 INTRODUCTION

Renewable energy is a type of energy obtained from

unlimited or inexhaustible natural resources, such as

wind and sunlight. Renewable energy is an alternative

to traditional energy that relies on fossil fuels, and

tends to be less harmful to the environment.

As the world's population increases, so does the

demand for energy to power our homes, businesses

and communities. Innovation and expansion of

renewable energy sources is key to maintaining

sustainable energy levels and protecting the planet

from climate change.

Fossil fuels are not renewable energy sources

because of their limited nature. Plus, they release

carbon dioxide into our atmosphere which contributes

to climate change and global warming.

Wind is a renewable energy source. This type of

energy is a clean energy source, meaning it does not

pollute the air like other forms of energy. Wind

energy does not produce carbon dioxide, or release

harmful products that can cause environmental

damage or have a negative impact on human health

such as smog, acid rain or other heat-trapping gases.

Wind farms capture wind energy using turbines

and convert it into electricity. Commercial grade wind

power generation systems can power communities.

https://orcid.org/0000-0001-5290-6910

https://orcid.org/0000-0002-6915-0475

The use of wind turbines requires wind farms that

are sufficiently strong and must meet a certain

minimum speed to operate, so they can only be

applied to certain locations that meet the requirements

for wind speed stability. An alternative technology

that can be used to utilize wind energy is to use a

fluttering flat plate. This technology is still at the

basic research stage. This technology is better known

as a wind harvester because it can be an alternative

solution for the use of wind energy in urban areas

where the wind flow is not so strong.

In this study, a new energy conversion design is

designed to convert the energy harvested by fluttering

thin–flat plates into electrical energy. This design of

several wind harvesters with various sizes of thin-flat

plates will be placed in the subsonic wind tunnel for

testing. The test includes measuring the energy

produced by the wind havester in the form of the

generated electrical voltage. The purpose of this study

was to determine the effect of the size of the thin-flat

plates on the electromotive force produced by a wind

harvester using an electromagnetic converter.

Rahtika, I., Suarta, I. and Rusmariadi, I.

The Application of Fluttering Thin-ﬂat Plates for Wind Harvesting using Electromagnetic Converter.

DOI: 10.5220/0010948100003260

In Proceedings of the 4th International Conference on Applied Science and Technology on Engineering Science (iCAST-ES 2021), pages 499-502

ISBN: 978-989-758-615-6; ISSN: 2975-8246

 2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)

499

2 THEORY

The main literature that forms the basis of this

research theory is knowledge about aeroelasticity,

especially about the flutter phenomenon.

Quite a lot of literature on flutter has been

published. In the history of flutter, the results of the

first theoretical study were carried out by Lord

Rayleigh (Rayleigh, 1878) who discussed the

instability of plates with infinite dimensions in axial

flow. A more practical scientific understanding of the

flutter phenomenon can be traced from the NACA

Technical Report No. 496 on General Theory of

Aerodynamic Instability and the Mechanism of

Flutter (Theodorsen, 1934). In that report,

Theodorsen explained theoretically how flutter could

occur in an airplane wing by explaining the

interaction between elasticity of structure, inertial

forces, and aerodynamic forces. The dynamics of the

airplane wing is modeled in mathematical form and

the solution of the model can explain the occurrence

of flutter. This research was continued as an

experimental investigation and reported in NACA

Technical Report No. 685 (Theodorsen, 1940). The

effect of adding Aeleron and Tab on flutter was

further reported in NACA Technical Report No. 736

(Theodorsen, 1941).

Flutter phenomena are also encountered in the

engineering world outside of aircraft. The collapse of

the Tacoma Narrows Bridge in the US state of

Washington in 1940 was finally concluded as a

design failure due to neglect of aerodynamic effects.

The bridge flutters when wind gusts with a speed of

48 km/hour come (Fox & McDonald, 1994).

The development of the printing industry requires

machines with higher speeds to motivate Watanabe et

al. (Watanabe, 2002a) investigated the flutter

problem on paper. There are two methods used,

namely potential flow and numerical Navier-Stokes

to describe the flutter mode shape as a function of

mass ratio. Time domain analysis was performed

using the Navier-Stokes method. Experimentally

Watanabe et al. (Watanabe, 2002b) observes the

minimum speed limit so that the paper stops

fluttering.

Fluid Structure Interaction (FSI) on a flag or long

ribbon has similarities to thin flat-plates. Research on

flags and long ribbons has been carried out by

Connell & Yue (2007), Lemaitre et al. (2005),

Michelin et al. (2008), Manela & Howe (2009), and

Virot et al. (2013).

With the advent of computer technology, many

flutter analysis uses the finite element method.

LAPAN researchers conducted a Flutter Analysis to

optimize the Fin design of the satellite launch rocket

(Andria, 2010). Manikandan & Rao performed the

finite element method to optimize the mounting

system of the aerofoil flutter test (Manikandan & Rao,

2011).

The bimodal flutter phenomenon was discovered

by Drazumeric et al. (2014) on a rigid airfoil that is

hung flexibly with a flexible plate mounted on the

trailing edge of the airfoil. The flutter behavior was

predicted using the eigenfunction expansion

approach and the bimodal flutter behavior was also

demonstrated experimentally.

Flutter in biological systems in humans was

investigated by Balint & Lucey (2005), Huang

(1995), and Howell et al. [2009]. They found that the

snoring phenomenon was similar to the flutter of the

cantilevered flexible plate in axial flow. The use of

flutter for wind energy harvesting has been explored

by Doaré & Michelin (2011) and Dunmon et al.

(2011). Other research on energy harvesting using a

slender structure behind the bluff body was also

conducted by Allen and Smits (2001) and Kuhl &

DesJardin (2012).

Previous works by authors include the study on

the flutter similitude of the free leading edge plates in

axial flow (Rahtika, 2017a), their numerical and

experimental investigation (Rahtika, 2017b), and the

effect of the angles of attack to the plate flutter

speeds. Another priliminary study on the application

of hidro flutter to field of renewable energy has also

been done by the authors (Rahtika, 2019).

Based on all these previous research, a new type

wind harvester was designed in ths research. The final

design of the wind harvester is shown on Figure 1.

Figure 1: The wind harvester design.

The basic working principle of the design is to

convert mechanical energy of fluttering magnetically

induced ferromagnetic plate into electrical energy

using solenoid. A ferromagnetic thin-flat plate will

experience a Limit Cycle Oscillation (LCO) when it

is placed in flowing air if the fow reach a certain range

of speed before the plate will experience unstability.

The plate absorbs energy from the flowing air and

saves it in the form of mechanical energy. Since the

wind direction

thin-flat plate

rectifie

permanent magnet

solenoi

iCAST-ES 2021 - International Conference on Applied Science and Technology on Engineering Science

500

plate is magnetically induced by a permanent

magnetic, its vibration will generate a fluctuating

magnetic field which induced an electromotive force

in the solenoid. Then, the generated current out of the

solenoid is rectified using a Wheatstone bridge

circuit.

3 RESULT

During the experiment, the thin-flat plate was placed

in a wind tunnel test chamber which had laminar

airflow. The thin-flat plate was clamped at one end

and left free at the other (cantilevered). The angle of

incidence was defined as the angle between the thin-

flat plate and the airflow. The angle of incidence is

defined as zero (0) if the free end is facing the wind.

The flutter speed is defined as the wind speed at the

time of plate instability.

A coil of conductor and permanent magnet was

placed on one side of the thin-flat plate which does

not move. Permanent magnets induced thin-flat plates

to become magnets. Thin-flat plate vibrated due to

flutter, and then induced coiling of the conductor to

produce electromotive force. The resulting

electromotive force will be recorded.

In step-by-step manner, the testing procedure

carried out in this study was as follows:

1. Thin-flat plate was placed in the wind tunnel

test chamber

2. The airflow waas increased slowly until the

thin-flat plate flutters.

3. The voltage generated by the coil is recorded.

4. Perform steps 1 to. 3 for the other plate

dimensions.

The experimental observation results from the

above test was analyzed qualitatively by paying

attention to the DC voltage generated out of

Wheatstone bridge restifier from three dimensions of

the thin-flat plate.

The DC volteges are the RMS values of the

voltages out of the solenoid. Table 1 shows the

voltages generated by the wind harvester with three

different plates’ thicknesses.

Table 1: RMS voltages of the wind harvester.

Plate thickness

(mm)

Voltage RMS

(Volts)

0.010 2.24

0.015 4.69

0.025 6.36

The voltage generated increased with the

increacing plate thickness because the thicker plate

has higher flutter speed and also has higher vibration

frequency during LCO which eventually would

generated higher voltage.

4 CONCLUSIONS

A wind harvester design using fluttering

ferromagnetic thin-flat plate has been constructed and

experimentally tested. Measurements have been

made to measure voltage produced with different

sizes of the wind harvester in a subsonic wind tunnel.

ACKNOWLEDGEMENTS

We would like to thank Bali State Polytechnics for

the funding that made this study could be completed.

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