Answer:
a) pressure drag is zero (0)
b) pressure drag is 20%
Explanation:
Ans) Given,
NACA 2412 airfoil
Re = 8.9 x 10^6
We know, for turbulent flow ,drag coefficient, Cdf = 0.074 / Re^0.2
=> Cdf = 0.074 / (8.9 x 10^6)^0.2
=> Cdf = 0.003
For both side of plate, Cd = 2 x 0.003 = 0.006
For zero degree angle of attack for NACA 2412, Cdf = 0.006
Also, Cd = Cdf + Cdp
=> 0.006 = 0.006 + Cdp
=> Cdp = 0
Hence, pressure drag is zero
Now, for zero degree angle of attack for NACA 2412, Cd = 0.0075
Also, Cd = Cdf + Cdp
=> 0.0075 = 0.006 + Cdp
=> Cdp = 0.0075 - 0.006
=> Cdp = 0.0015
Hence, Pressure drag percentage = (Cdp / Cdf) x 100
=> Pressure drag percent = (0.0015/0.0075) x 100 = 20 %
Hence, pressure drag is 20% of pressure drag due to flow seperation Ans) Given,
NACA 2412 airfoil
Re = 8.9 x 10^6
We know, for turbulent flow ,drag coefficient, Cdf = 0.074 / Re^0.2
=> Cdf = 0.074 / (8.9 x 10^6)^0.2
=> Cdf = 0.003
For both side of plate, Cd = 2 x 0.003 = 0.006
For zero degree angle of attack for NACA 2412, Cdf = 0.006
Also, Cd = Cdf + Cdp
=> 0.006 = 0.006 + Cdp
=> Cdp = 0
Hence, pressure drag is zero
Now, for zero degree angle of attack for NACA 2412, Cd = 0.0075
Also, Cd = Cdf + Cdp
=> 0.0075 = 0.006 + Cdp
=> Cdp = 0.0075 - 0.006
=> Cdp = 0.0015
Hence, Pressure drag percentage = (Cdp / Cdf) x 100
=> Pressure drag percent = (0.0015/0.0075) x 100 = 20 %
Hence, pressure drag is 20% of pressure drag due to flow seperation
