EFFECTS OF THICKNESS AND CAMBER RATIO ON FLOW CHARACTERISTICS OVER AIRFOILS

İlyas Karasu,Mustafa Serdar Genç,Kemal Koca,Halil Hakan Açikel

doi:10.18186/thermal.710967

İlyas Karasu, Mustafa Serdar Genç + Show 2 more

Open Access

https://doi.org/10.18186/thermal.710967

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Abstract

This study ensures experimental and numerical investigation of different airfoils to observe and understand how camber ratio affects the flow characteristics over surface of different airfoils. Experimental results in the previous studies were used while the numerical study was performed for present investigation. Reynolds numbers based on the airfoil chords were 1x105 and the angle of attack of 8°. Instantaneous voltage output data were used in order to detect transition location for NACA 4412, oil surface visualization experiments were presented for NACA 2415. In the numerical analysis, values of u/U∞ and turbulent kinetic energy were presented for NACA 4415 airfoil. The experimental results denoted that the change of camber ratio and thickness significantly affected the flow phenomenon such as boundary layer separation or formation and progress of the laminar separation bubble. The long bubble was clearly observed with accumulation of pigments at oil-flow measurement experiment. By increasing the camber ratio with the use of NACA 4412 airfoil, the long bubble turned into the short bubble. Briefly, not only the progress and formation of laminar separation bubble was being affected, but also the onset of transition point was obviously influenced by changing of camber ratio.

Highlights

For over 75 years, there are many studies and investigations with regards to boundary layer transition over the surface of airfoil or wind turbine blade especially at operating low Reynolds number, but it still remains as a subject of research
The statements like flow separation or laminar separation bubble (LSB) which affects the aerodynamic performance can be observed at boundary layer separation happening on the suction side of airfoil because of adverse pressure gradient (APG)
In terms of explaining aerodynamic phenomenon in accordance with thickness and camber variation, the objective of this study is to investigate the thickness and camber effects on aerodynamic performance of different airfoils

Summary

INTRODUCTION

For over 75 years, there are many studies and investigations with regards to boundary layer transition over the surface of airfoil or wind turbine blade especially at operating low Reynolds number, but it still remains as a subject of research. The statements like flow separation or laminar separation bubble (LSB) which affects the aerodynamic performance can be observed at boundary layer separation happening on the suction side of airfoil because of adverse pressure gradient (APG). LSB over an SD7003 airfoil was experimentally analyzed by Burgmann and Schröder [13] at low angle of attacks and Reynolds number ranging from 2x104 to 6x104 They examined that no steady formation statement was observed in zone of transitioning shear layer. Transition phenomenon as well as formation and characteristics of LSB, which was negative statement for aerodynamic performance of wind turbine airfoils, were investigated at Reynolds number of 1x105 and angle of attack of 8o. Air density was taken as 1.05 kg/m3, which was used as same value for experiments

EXPERIMENTAL RIGS AND TEST SAMPLE

Overview of Experimental Results and Comparison with Numerical Study

Findings

CONCLUSION