Calculation of Drag Coefficient for Airfoil

fredi · September 26, 2021, 16:41

Hi eveyrbody and thanks for visiting this thread,

I have studied some texts on Aerodynamics and my problem is that majority of them address calculation of lift (Cl) and systematic calculation of drag is non existent among those books.

My problem is how to calculate the drag(Cd) coefficient (specifically for NACA 4412 and in general)

My guess is that I have to calculate it by integration of the tension and pressure on airfoil but that laves me with a lot of unknown quantities like pressure distribution and etc.

Is there a simpler root for that? How will I then proceed to find CD? How does the body of vehicle affect the drag beside airfoil and wing?

Thanks in advance

LuckyTran · September 26, 2021, 17:16

It's the exact same concepts as lift except along a different direction. Lift force is up whereas drag force is in the direction of travel. That's all.

fredi · September 27, 2021, 16:39

Thanks,

How do I calculate Cd (or CD) drag coefficient? I have found in a textbook that it is equal to 0.01 for 8 degrees of angle of attack and I do not know how to find it.

More importantly considering that Cl is equal to 0.42 in 8 degrees of AOA then I get for L/D = 42 which does not seem to be correct.

I think I am doing a big mistake somewhere.

any detailed discussion on this somewhere?

fredi · September 28, 2021, 07:57

Never mind, I figured that out.

I was doing sth wrong about the AOA and I found it.

Thanks anyway.

September 26, 2021, 16:41	Calculation of Drag Coefficient for Airfoil	#1
fredi New Member Please select a state (mandatory for US) Join Date: Jul 2021 Posts: 13 Rep Power: 4	Hi eveyrbody and thanks for visiting this thread, I have studied some texts on Aerodynamics and my problem is that majority of them address calculation of lift (Cl) and systematic calculation of drag is non existent among those books. My problem is how to calculate the drag(Cd) coefficient (specifically for NACA 4412 and in general) My guess is that I have to calculate it by integration of the tension and pressure on airfoil but that laves me with a lot of unknown quantities like pressure distribution and etc. Is there a simpler root for that? How will I then proceed to find CD? How does the body of vehicle affect the drag beside airfoil and wing? Thanks in advance

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September 26, 2021, 17:16		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,674 Rep Power: 66	It's the exact same concepts as lift except along a different direction. Lift force is up whereas drag force is in the direction of travel. That's all.

September 27, 2021, 16:39		#3
fredi New Member Please select a state (mandatory for US) Join Date: Jul 2021 Posts: 13 Rep Power: 4	Thanks, How do I calculate Cd (or CD) drag coefficient? I have found in a textbook that it is equal to 0.01 for 8 degrees of angle of attack and I do not know how to find it. More importantly considering that Cl is equal to 0.42 in 8 degrees of AOA then I get for L/D = 42 which does not seem to be correct. I think I am doing a big mistake somewhere. any detailed discussion on this somewhere?

September 28, 2021, 07:57		#4
fredi New Member Please select a state (mandatory for US) Join Date: Jul 2021 Posts: 13 Rep Power: 4	Never mind, I figured that out. I was doing sth wrong about the AOA and I found it. Thanks anyway.