بررسي تجربي تاثير نسبت منظر بر ضريب درگ يك لوله بادامكي

An experimental study on drag coefficient of a cam-shaped tube with different aspect ratios

در اين مطالعه تاثير نسبت منظر بر ضريب درگ يك لوله بادامكي در جريان عرضي هوا به صورت تجربي بررسي شده است. محدوده اعداد رينولدز بر اساس قطر معادل لوله دايروي 25000 تا 55000 و زاويه حمله صفر و 180 درجه انتخاب شده است. نتايج نشان مي دهند كه با افزايش نسبت منظر، ضريب درگ لوله بادامكي كمتر مي شود بطوريكه ضريب درگ در زاويه حمله صفر و 180 درجه به ترتيب حدود 54 تا 82 درصد و 42 تا 82 درصد نسبت به لوله دايروي با قطر معادل كاهش يافته است. همچنين كمترين ضريب درگ در هر دو زاويه حمله مربوط به نسبت منظر 3.13 مي باشد

An experimental study has been conducted to show the effect of aspect ratio (L/D) on drag coefficient of a cam-shaped tube in cross-flow of air. Five aspect ratios have been considered, which vary between 1.35 ≤ L/D ≤ 3.13 and Reynolds number based on equivalent diameter changes in the range of 2.5×103 to 5.5×103. Tubes have the same circumference, and their equivalent diameter are 38.1 mm. Studies were carried out at zero and 180-degrees angle of attack. Results show that by increasing the aspect ratio, drag coefficient of the cam-shaped tube decreases, therefore the average drag coefficient at zero-angle of attack for tube number 1 to 5 decreases about 54-82% in comparison to a circular tube with an equivalent diameter. Also, the average drag coefficient for tube number 1 to 5 at 180-degrees angle of attack decreases about 42-82%, compared to the circular tube. Moreover, it was found that the camshaped tube with L/D = 3.13 has the minimum drag coefficient in both angles of attack, which is about 82% lower than the circular ones.