Air Vehicles Technology Integration Program (AVTIP). Delivery Order 0020: Prediction of Manufacturing Tolerances for Laminar Flow
Final rept. 1 Dec 2003-30 Jun 2005
NORTHROP GRUMMAN CORP EL SEGUNDO CA AIR COMBAT SYSTEMS
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An examination of the effects of surface excrescences on boundary layer transition has been performed, including both experimental and computational components. The experimental study focused on stagnation-line starting condition boundary layers in incompressible flow without sweep effects. The study was performed at low-Reynolds number-less than 106-and included the effects of both adverse and favorable pressure gradients. The results for both forward and aft-facing steps indicate a substantial stabilizing effect of favorable pressure gradient on excrescence-induced boundary layer transition. These findings suggest that manufacturing tolerances for laminar flow aircraft could be loosened in areas where even mild favorable pressure gradients exist. The present study, due to its limited scope, does not provide sufficient basis for setting actual manufacturing tolerances however, it provides a solid foundation on which follow-on examinations including compressibility effects can be built.
- Fluid Mechanics