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April 21, 2018, 14:51 
Thrust Coefficient vs. Drag Coefficient

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Matt Ridzon
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Admittedly, I'm ignorant of what the Thrust Coefficient of an airfoil is. I've only ever studied lift and drag coefficients of an airfoil, but never thrust coefficients in an academic setting. However, after a little digging through textbooks and some web searches, the thrust coefficient equation appears identical to that of the lift and drag coefficients. So intuition tells me the thrust acts opposite of drag, therefore the thrust coefficient would be identical to the drag coefficient but opposite in sign. Is my understanding correct?
Just as background information, here's what I'm doing...I am modeling an airfoil in Fluent and will extract its drag, lift, and thrust coefficients from steadystate laminar flow with low Re. Thanks in advance, M Ridzon 

April 23, 2018, 00:55 

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Lucky
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During aerial manuevers (i.e. turns, banks, looptheloops), part of the airfoil reaction forces can be in the direction of acceleration so that the thrust coefficient is not always equal and opposite the drag because the drag in the direction of the velocity.
The coefficients are all positive. 

April 23, 2018, 09:25 

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Matt Ridzon
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Quote:
M Ridzon 

April 23, 2018, 14:53 

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Never heard of thrust coefficient for an airfoil. I've always used thrust coefficient for jet nozzle thrust. There is the concept of leadingedge suction for airfoils.


April 23, 2018, 15:22 

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Matt Ridzon
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M Ridzon 

April 23, 2018, 17:20 

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Just had another thought: for flapping wings, .e.g. birds and insects or ornithopters, the concept of thrust coefficient may be appropriate. Also for rotors and propellers which use airfoil sections 

April 24, 2018, 08:43 

#7 
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Matt Ridzon
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Yes, thank you. My college colleague affirmed this also, noting that experts in the area of flapping wing technology use the idea of "thrust coefficient" to help define their research findings. And that is precisely the area of my current work is in.


April 24, 2018, 12:01 

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Please keep us posted on your work! 

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drag coefficient, lift coefficient, thrust 
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