The discussion revolves around the concept of drilling tiny holes in wings to manipulate the boundary layer, with references to various experimental approaches and their implications for aerodynamics. Participants explore the effectiveness of different methods, including laminar flow control, vortex generators, and the use of blown flaps, while also sharing anecdotal experiences and research findings related to airflow management in aviation and automotive contexts.
Participants express a range of views on the effectiveness and practicality of different methods for managing boundary layers, indicating that multiple competing perspectives exist. The discussion remains unresolved regarding the best approach to take.
Some claims depend on specific conditions or assumptions about airflow dynamics, and the effectiveness of various methods may vary based on application and design constraints. There are unresolved questions about the long-term viability of drilled holes in wings and their susceptibility to clogging.
http://en.wikipedia.org/wiki/Blown_flapIn a conventional blown flap a small amount of the compressed air produced by the jet engine is "bled" off of the compressor stage and piped to channels running along the rear of the wing. There it is forced through slots in the wing flaps of the aircraft when the flaps reach certain angles. This air follows the flap profile, aimed downward to provide more lift. The bleed air prevents the boundary layer (slow-moving air that accumulates on the airframe surface) on the upper surface of the flap from stagnating, further improving lift. At low speeds the amount of air being delivered by this system can be a significant fraction of the overall airflow, generating as much lift as if the plane were traveling at much higher speeds.
turbo-1 said:I don't know about that, Woolie, but I have a friend who has been the National champion in his drag-racing class (he runs a classic 340 Duster) and is always competitive. He claims that if you polish intake manifolds, it supports laminar boundary-flow and that causes drag. He has his intake manifolds roughened to some arcane standards that he and his head-work specialist know, and he claims that the micro-turbulence in the air/manifold boundary acts like "little ball-bearings" as he puts it, to allow the bulk of the intake air to get to the cylinders with as little drag as possible. It makes sense, because if you can get the air rolling in little tiny pockets and the air is rolling to counter to the bulk air flow just at the boundary, and is rolling IN the direction of the bulk air flow just a little bit away from the air-manifold boundary, the bulk of the air would get a little boost from the rotating air cells near the boundary. He races in a class that is very restrictive about the modifications that are allowed to the car, so every little secret helps.
russ_watters said:It actually goes both ways depending on how you are looking to do it. I have to run, but here's a link to the opposite: http://en.wikipedia.org/wiki/Blown_flap
wolram said:Is this like a venturi effect?
Mech_Engineer said:An aero professor and some grad students at my university were developing a wing that instead of using control surfaces used tons of tiny holes on the top and bottom of the wing of the aircraft. Using an internal pump and ducting to the holes, they directly changed the pressure above/below the wing to control the aircraft's flight, taking over control which would normally be accomplished through control surfaces on the wing.
FredGarvin said:I'll have to see if I can dig up any results or reports.
pantaz said:The holes in the wings clogged too easily to make the system worthwhile.
wolram said:Hi pantaz, did you work with this idea, if so do you have any data.