Expert: Paul Soderman - 5/15/2009

Question
QUESTION:  Good day sir i would like to have answers and/or information on where to get detailed answers to the following questions:
- How does one compress air aerodynamically? (The generally idea, then any device or system for such purpose)
- How much of internal piping in a wing is too complicated?
- What is the efficiency(advantage) of jet flaps especially over oter methods of high lift?

ANSWER: Air follows the gas laws which show that density, pressure, temperature and volume are related.  Air can be compressed (density change) by changing pressure, temperature or volume.  Changing airspeed can change pressure.  And forcing air through a constriction such as a wind tunnel test section changes pressure and volume.

I am not sure what you mean by complicated piping.  All ducts in wings serve a purpose, but there is always the possibility that design changes could make thinks simpler.  To do that you would be competing with design engineers who work on that as part of the aircraft development.

Jet flaps have the advantage over normal flaps that the added flow energy entrains flow and adds momentum that increases flap performance.  The disadvantage is that you have to supply that energy and ducting and weight to make it happen.  But aircraft have been designed to do just that.
Paul

---------- FOLLOW-UP ----------

QUESTION: Can you give me information on where to find the derivation of the velocity field (of the vortex)of a wing with endplates

Answer
Not specifically, but the endplates can be modeled by a grid of vortices that support the boundary condition of no flow through the surface.  J. Katz and A. Plotkin discuss vortex grid generation for arbitrary surfaces in Low-Speed Aerodynamics, Cambridge U. Press 2001 (2nd edition).  See the chapter on Two-Dimensional Numerical Solutions.  They also discuss the classical horseshoe vortex modeling of a wing.
Paul