Aerodynamic low drag structure

An aeroengine nacelle structure including an intake duct, comprising

• a lipskin defining an intake throat leading into the intake duct and including a noise attenuation panel having a facing component part with a front face which forms a boundary surface of the intake duct and which is subjected to fluid flow over it in a boundary layer adjacent the boundary surface, the facing component part of the noise attenuation panel having a plurality of flow apertures which extend through the facing component part at a downstream region of the attenuation panel and at an upstream region of the attenuation panel, the downstream region and the upstream region defining end portions of the intake duct between which shockwave induced pressure gradients are generated, the noise attenuation panel further having a cellular component part adjoining a rear face of the facing component part, the cellular component part having fluid communication path means for withdrawing gaseous fluid from a high pressure region of the boundary layer through the apertures at the downstream region of the attenuation panel, conveying within the cellular component part and discharging through the apertures at the upstream region of the attenuation panel into a low pressure region of the boundary layer to control boundary layer separation of the boundary layer from the boundary surface of the attenuation panel arising from shockwave induced pressure gradients in the boundary layer.