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In addition to winglets and other techniques like sweeping wing back what are the other techniques that delay the formation of local shock wave over the wing?

sophit
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Ambarish Deshpande
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    Welcome to Stack Exchange! Your question is a little confused, in the sense that you are asking two questions in one post. Could you please align the question title and question body? – Kenn Sebesta Feb 17 '24 at 14:44

2 Answers2

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Winglets are not used to delay shocks. They help to squeeze a bit more lift from a wing and reduce induced drag for a wing of given span.

Winglets help to increase the pressure difference between the top and bottom side of the wing near the tip. This leads to higher overspeeds and earlier shock formation. Note that in a well balanced design the first shocks appear at about the same speed over the whole wingspan, so adding a winglet will let shocks appear first near the tip and a slightly lower speed.

The prevailing techniques for delaying the formation of shocks are to:

  • fly more slowly. Especially for turns or pull-ups, speed should be reduced beforehand.
  • increase wing sweep.
  • adjust pressure distribution over chord such that suction peaks are avoided. This means that most lift will be created by rear loading, so a larger horizontal tail and more torsional stiffness of the wing are required.
Peter Kämpf
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    To anonymous downvoter: Why did you downvote this answer? Do you disagree with the statements contained in it? – End Anti-Semitic Hate Feb 17 '24 at 17:49
  • I edited the title to reflect the body of the question, you might want to adjust your answer consequently. +1 from my side – sophit Feb 17 '24 at 20:20
  • Sorry if I'm not picking something up in the provided link, but what is meant by rear loading? Also +1 from me – Wyatt Feb 17 '24 at 20:52
  • @Wyatt Rear loading means litte camber in the thick forward part of an airfoil and high camber in the thinner, rear part. This shifts lift production especially at low angle of attack to the rear part of the chord. – Peter Kämpf Feb 18 '24 at 00:40
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In addition to Peter Kämpf's fine answer, shocks can be weakened, delayed, or avoided by:

  • Reducing thickness of the wing.
  • Reducing lift coefficient (related to his turns and pull-ups comment)
  • Local area relieving where lifting surfaces meet non-lifting surfaces. For example, coke-bottling a tip tank can prevent the superposition of two areas of super-velocities.
Rob McDonald
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