Can surface roughness on wings improve performance

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Discussion Overview

The discussion centers on the effect of surface roughness on wing performance, particularly in relation to drag and flow transition. Participants explore various concepts including turbulators, vortex generators, and the implications of surface roughness in both experimental and practical applications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant notes that while surface roughness typically increases drag, some research suggests that carefully selected roughness can suppress turbulent flow by delaying the transition point on the wing.
  • Another participant explains that the purpose of roughness or turbulators is to induce an earlier transition from laminar to turbulent flow to reduce separation bubbles, which can increase profile drag.
  • There is mention of using 600 grit sandpaper on fiberglass gliders to create surface roughness, along with oil flow tests to visualize flow separation.
  • A participant questions the absence of turbulators in commercial aircraft, seeking clarification on this point.
  • Vortex generators are introduced as a related concept, with a reference provided for further reading.

Areas of Agreement / Disagreement

The discussion reflects multiple competing views regarding the effects of surface roughness and the use of turbulators and vortex generators. Participants express uncertainty about the application of these concepts in commercial aviation.

Contextual Notes

Participants note the difficulty in finding research papers on the topic and the potential variability in the effectiveness of surface roughness depending on specific conditions and applications.

Who May Find This Useful

This discussion may be of interest to students and researchers in aerospace engineering, as well as hobbyists involved in glider design and performance optimization.

MattH150197
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Homework Statement


I have a project to research the effect of surface roughness on wing performance. I found mostly that roughness leads to increased drag on a wing, however came across a website that briefly spoke about how recently researchers have observed how carefully selected roughness can suppress turbulent flow on the wing by delaying the transition point so that it is further back on the wing or even past the wing. However i am struggling to find actual research papers on this so does anyone know where to find more information on this, or could share any knowledge that you have on this subject yourself. Thanks!
 
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The idea of roughness or a turbulator is to cause the transition from laminar to turbulent flow to occur sooner, to reduce or avoid a separation bubble that increases profile drag. For fiberglass gliders, 600 grit wet sandpaper may be used to rough up the wings.

Since the links to web sites often change, I recommend doing a web search for "glider 600 grit" and also "glider oil flow". Oil flow tests involve putting a thin layer of oil on a wing, flying or testing the wing at speed, and noticing where the oil is not blown off by the air flow, which indicates a separation bubble.
 
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Thanks for the quick responses! I've had a quick research on turbulators but it seems that they are not used on commercial aircraft, unless I am mistaken which i may be, why is this?
 
Perhaps see also...
http://www.edge.aero/single-post/2016/04/17/Taming-Turbulence-With-Tape-Conformal-Vortex-Generators
 
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