Strake sizing

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addaon

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Anyone have any documents about strake sizing? The concept is a bit late for NACA, unfortunately…
 

addaon

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Yeah, that's actually a great paper. The downside is that almost all of the considerations are at Mach 0.8… there's Mach 0.2 data, but not much of it.

The punchline is Figure 44. It defines a an effectiveness parameter of ∂CL * (Sref / Aeff), where Aeff is the area "effected by" the strake (that is, the projected area from the strake leading edge to the wing trailing edge in the direction of flight). Values of Sref / Aeff investigated range from 3.15 to 8.20. At least towards the bottom of this range (larger strakes), there's a pretty consistent behavior of the effectiveness parameter. Change in lift is negligible below 8°, moderate at best below 16°, and significant above that. At 16°, effectiveness is about 0.3 ∂CL * (Sref / Aeff) without LE flaps, corresponding to a ∂CL of about 0.1 for the largest strakes considered in this condition (Mach 0.8, 16° AoA).
 

JamesG

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"bigger isn't always better"?
I think they were only examining the airflow and lift generated under those conditions for those configurations without consideration of the practical ramifications on a real aircraft.
 

addaon

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I think they were only examining the airflow and lift generated under those conditions for those configurations without consideration of the practical ramifications on a real aircraft.
Disagree, all the configurations considered were under real consideration for the YF-16 project. And in terms of practical ramifications, there's significant discussion about the impact on stability, etc. The paper is basically an attempt to distill a huge amount of experimental data into some empirical rules, in the absence of the ability to actually compute behavior; and it does a good job of that (if you're going Mach 0.8), for sane (if not particularly systematic) geometries.
 
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