| 摘要 |
Boundary layer separation at the surface of a structure such as an intake duct (18) (Fig. 1) of a turbofan aeroengine nacelle (12) at conditions of high incidence and high engine mass flow arises from shockwave induced pressure gradients in the boundary layer. To control separation, gaseous fluid is withdrawn from a high pressure region of the boundary layer downstream of a shock wave 27, conveyed within the intake duct structure and discharged upstream of the shockwave into a low pressure region of the boundary layer. The intake duct (18) embodies a noise attenuation panel 19, and fluid is withdrawn from the high pressure region of the boundary layer into a modified panel section 191 by passage through apertures 30 at a downstream region of the panel section, conveyed along a fluid communication path within the panel section 191 and discharged into the low pressure region of the boundary layer by passage through apertures 30 at an upstream region of the panel section 191. Gaseous fluid is conveyed solely as a consequence of the difference in pressures in the boundary layer at the downstream and upstream regions. The panel section 191 may comprise a cellular structure 151, sandwiched between a porous facing sheet 122 and a backing sheet 11, the cells communicating by means of slots 31. <IMAGE>
|
