Characterization And Testing Of Piv Illumination System Using High Power Led On Naca 0018 Airfoil At Low Reynolds Number
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Date
2018-10-01
Authors
Lai, Hoong Chuin
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
This thesis reports the work on characterization and evaluation of the particle
image velocimetry (PIV) illumination system using high power light emitting diode
(HPLED). An illumination system using these HPLEDs was developed with the
custom-built driver circuit. The driver circuit and the HPLEDs were characterized.
As a result, input transistor-transistor logic (TTL) signal and the metal oxide
semiconductor field effect transistor (MOSFET) output signal for the driver circuit
were compared while emitted wavelength by the HPLEDs at different power levels
and pulsing frequencies were measured. The HPLEDs emitted light with wavelength
that is located at the peak of the spectral sensitivity of the imaging device. The light
intensity emitted by the HPLED is also found to be increasing linearly together with
the power supplied. The evaluation of the developed illumination system was
performed by investigating the case study of flow field across the impulsively started
NACA 0018 airfoil in a water tank. The airfoil was set at various angles of attack
ranging from 0°to 45°with intervals of 5°, with both flow Reynolds numbers of
6740 and 9235. Qualitative and quantitative comparisons were made on images
acquired by both illumination systems. Lift force generated were also measured at
the same time to justify the results obtained from the flow measurement. Images
acquired were analyzed using PIVLab, a MATLAB based PIV correlation software.
Both flow fields for steady and unsteady cases were successfully investigated.
Through the case studied, the advantages and limitations of the developed
illumination system could be determined. It showed that HPLEDs promises several
advantages in terms of cost, safety and performance. Similar performance to the laser
illumination system can be achieved but only requires 10% of its cost by using the
HPLEDs illumination system. It has a high potential to be developed into an
alternative to replace the laser-based illumination system for PIV in the near future.