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The Effects of Surface Roughness on the Characteristics of Surface Pressure of NACA 0015 Airfoil
|關鍵字:||NACA airfoil series;NACA系列機翼;Reynolds number;surface roughness;sandblast;雷諾數;表面粗糙度;噴砂||出版社:||機械工程學系||摘要:||
本文研究是以實驗方法探討二維對稱機翼模型（NACA 0015）表面因噴砂所造成表面各種粗糙度對機翼上下表面壓力變化之影響。實驗工作於低速開放式風洞中進行，自由流速所對應之雷諾數範圍為3.8×104~1.5×105，實驗之參數為攻角α（α=0°, 5°, 10°, 15°, 20°）、雷諾數Re（3.8×104~1.5×105）、噴砂號數（#100, #150）以及噴砂寬度w（w=1, 2, 3 mm）。本文首先探討不同實驗參數對機翼表面壓力變化分佈及機翼面受力之影響，進而找出不同噴砂參數與機翼表面壓力之間的對應關係。
本文研究結果顯示，在不同實驗參數下機翼表面壓力之變化程度會有不同的分佈型態。當流速為低雷諾數（Re≦3.8×104）時，噴砂效應對機翼表面壓力的影響並不明顯；當高雷諾數（Re≧1.1×105）時，噴砂效應對機翼表面壓力分佈則產生較顯著的影響。本文發現噴砂寬度對機翼表面壓力分佈產生之壓升效應並非呈現線性關係，因為機翼表面之壓升動力行為在噴砂寬度w=3 mm時並沒有達到最大，反而在噴砂寬度w=2 mm時達到最大值。另外，在噴砂號數的影響方面，當自由流速為20 m/s且機翼攻角為5與10度下，噴砂號數為#100時在翼前緣附近分別產生較明顯之壓降現象與壓升動力行為。此壓降現象隨著自由流速與噴砂寬度增加而變大，且壓升動力行為會有明顯往翼前緣移動之現象，但噴砂號數為#150時之壓升現象並不明顯。
The present study was intended to investigate the surface pressure of NACA 0015 airfoil at upper and lower surface due to the sandblast roughness. The experiment was proceeded in an low-speed and open-type wind tunnel. The dynamic behavior of surface pressure of NACA 0015 airfoil was analyzed at various angle of attack, Reynolds number, number of sandblast, and width of sandblast. The freestream velocity was operated at 5~20 m/s and the corresponding Reynolds number at 3.8×104~1.5×105 which based on the chord of the wing. The purpose of this study was intended to understand the relation between surface pressure of the airfoil and parameters. The surface pressure of NACA 0015 had measured and analyzed the aerodynamic performance and flow field characteristics of NACA 0015 airfoil.
The experimental results was shown that a parameter of sandblast was one of important parameters to affect the flow field. The parameter of sandblast was not apparent to affect the flow field at low Reynolds number, but it appeared gradually dominated at higher Reynolds number. The general phenomena of the surface pressure drop increased with more sandblast width was not shown in this study. Moreover, the pressure drop phenomenon and the pressure lift dynamic behavior respectively near the leading edge when angle of attack were 5° and 10°, freestream velocity was 20 m/s, number of sandblast was #100. The pressure drop phenomenon beacame large with increasing the freestream velocity and width of sandblast, and the pressure lift dynamic behavior moved forward to the leading edge obviously. However, the phenomenon of rising pressure for sandblast number #150 wasn't shown apparently. The present results can be provided to the references for the defense industry.
|Appears in Collections:||機械工程學系所|
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