Drag Coefficient -- What is the constant K?

AI Thread Summary
The drag coefficient (CD) is initially represented as CD=CD0+CL/πAe, assuming a linear relationship with lift (CL) for small flight conditions. A new formula introduced by the professor, CD=CD0+k1CL+k2CL^2, incorporates constants k1 and k2, allowing for a more accurate representation of CD over a broader range of flight conditions where the relationship begins to curve. The constant K reflects the induced drag due to lift, which is influenced by factors like pressure differences and downwash around the wing. Estimating k1 and k2 is essential for accurate modeling, though it complicates the analysis due to nonlinearity. Understanding these constants is crucial for analyzing drag in various flight scenarios.
eliasss
Messages
1
Reaction score
0
TL;DR Summary
What is the constant K in the drag coefficient?
As I understand, the drag coefficient looks as follows:

CD=CD0+CL/πAe

however, the professor threw in a new constant, K, and I am having trouble understanding what this means. The formula now looks like this:

CD=CD0+k1CL+k2CL^2

could someone help? Thanks!
 
Physics news on Phys.org
Welcome to PF.

Maybe one is the induced drag, that is due to air moving around the end of the wing.
Induced drag is proportional to lift, not to the square of the airspeed.
 
eliasss said:
TL;DR Summary: What is the constant K in the drag coefficient?

As I understand, the drag coefficient looks as follows:

CD=CD0+CL/πAe
This assumes that CD is a linear function of CL, which is an ok assumption as long as you are linearizing in a small region of flight condition.
There are good reasons to analyze stability and control in small flight condition regions using linearized equations.
eliasss said:
however, the professor threw in a new constant, K, and I am having trouble understanding what this means. The formula now looks like this:

CD=CD0+k1CL+k2CL^2
This models CD as a function of CL and CL^2. It allows more accuracy for a larger region of flight condition where the relationship between CD and CL has begun to curve. The parameters, k1 and k2 need to be estimated. k1 is probably very close to ##1/(\pi A e)##. But a lot of analysis gets much more difficult when the equations are nonlinear.
CORRECTION: There is no reason to think that k1 is close to ##1/(\pi A e)##. I was thinking that it was a Taylor series expansion around the linearization point.
 
Last edited:

Thread 'Radiation Hard Electronic Design for LVO Long Mission'

Venus does not have a magnetosphere, so the Galactic Cosmic Rays (GCRs) environment shall be much worse than in a LEO environment. Looking to the std radiation models for Venus, the standard radiation-hard space level electronic component with tested immunity LET = 85 MeV-cm2/mg seems not enough, so, for example, a 1cm2 Si die will suffer considerable flux above this level during a long mission (10 years for example). So, the question is, usually we are not paying attention to latch-up...
View full post »

Thread 'Space Stuff and Launch Info'

Due to the constant never ending supply of "cool stuff" happening in Aerospace these days I'm creating this thread to consolidate posts every time something new comes along. Please feel free to add random information if its relevant. So to start things off here is the SpaceX Dragon launch coming up shortly, I'll be following up afterwards to see how it all goes. :smile: https://blogs.nasa.gov/spacex/
View full post »
Thread 'SpaceX Starship development: 7th flight January 10'

Thread 'SpaceX Starship development: 7th flight January 10'

Watch the progress live This is a fully stacked Starship (top) and Super Heavy (bottom). A couple of too-small-to-see cars near the bottom for scale, I also added a Saturn V and the Statue of Liberty for comparison. 120 meters tall, about 5000 tonnes when fully fueled. Twice the mass and over twice the thrust of Saturn V. The largest rocket ever built by mass, thrust, height, and payload capacity. N1 had the largest diameter.[/size] But its size is not the revolutionary part. It is designed...
View full post »

Similar threads

I don't understand how to calculate the drag coefficient
Replies
7
Views
3K
How to Approximate Aerodynamic Coefficients? (Lift/Drag)
Replies
1
Views
3K
What factors affect a golf ball's drag and lift besides spin and speed?
Replies
2
Views
3K
Aerodynamics- Coefficient of Drag
Replies
2
Views
4K
Understanding Drag and Coefficient of Drag (Cd) in Aero Engineering
Replies
11
Views
6K
How to find drag polar equation of Cl vs Cd graph
Replies
4
Views
9K
Effect of Surface Area on the Drag Coefficient of a Parachute
Replies
6
Views
4K
Help with drag coefficient calculated from ballistic coefficient
Replies
3
Views
7K
How to estimate a constant drag coefficient of a boat?
Replies
8
Views
7K
I Drag Coefficient of a 'flexible' object (e.g. a piece of paper)
Replies
4
Views
2K

Hot Threads

Recent Insights

Back
Top