Based on our preceding studies on the aerodynamics of a falcoperegrinus in diving flight along a vertical dam it is known that even when the body shape of the bird is rather streamlined in V-shape some feathers tips m...Based on our preceding studies on the aerodynamics of a falcoperegrinus in diving flight along a vertical dam it is known that even when the body shape of the bird is rather streamlined in V-shape some feathers tips may elevate in certain regions of the body. These regions were identified in wind tunnel tests for typical diving flight conditions as regions of locally separated flow. A life-size model in V-shape of a falcoperegrinus with artificial feathers fixed along the body was studied in a wind tunnel to focus on the fluid-structure interaction of feathers located in this sector. The distal ends of the feathers show flow-induced vibrations at typical flight conditions which grow linear in amplitude with increasing angle of incidence until incipient separation. In light of the proven existence of vibration-sensitive mechanoreceptors in the follicles of secondary feathers in birds it is hypothesized that this linear amplitude response offers the bird to sense the angle of incidence during the diving flight using the vibration magnitude as sensory stimulus. Thus the bird in streamlined shape has still a good measure to control its attitude to be in the narrow window of safe angle of incidence. This might have implications also for other birds or technical applications of airfoil sensors regarding incipient separation detection.展开更多
During earlier research on shock wave/boundary layer interaction control, the effect of air humidity flow separation has been observed. This has inspired a more detailed study on the effect of air humidity on shock in...During earlier research on shock wave/boundary layer interaction control, the effect of air humidity flow separation has been observed. This has inspired a more detailed study on the effect of air humidity on shock induced incipient separation and on the involved involved processes. The phenomenon has a twofold nature. In supersonic flow, the condensation of humidity causes flow retardation due to heat addition. The consequent weakening of the shock wave reduces the tendency towards separation. On the other hand, the incipient separation is postponed at the same Mach numbers of interaction.展开更多
文摘Based on our preceding studies on the aerodynamics of a falcoperegrinus in diving flight along a vertical dam it is known that even when the body shape of the bird is rather streamlined in V-shape some feathers tips may elevate in certain regions of the body. These regions were identified in wind tunnel tests for typical diving flight conditions as regions of locally separated flow. A life-size model in V-shape of a falcoperegrinus with artificial feathers fixed along the body was studied in a wind tunnel to focus on the fluid-structure interaction of feathers located in this sector. The distal ends of the feathers show flow-induced vibrations at typical flight conditions which grow linear in amplitude with increasing angle of incidence until incipient separation. In light of the proven existence of vibration-sensitive mechanoreceptors in the follicles of secondary feathers in birds it is hypothesized that this linear amplitude response offers the bird to sense the angle of incidence during the diving flight using the vibration magnitude as sensory stimulus. Thus the bird in streamlined shape has still a good measure to control its attitude to be in the narrow window of safe angle of incidence. This might have implications also for other birds or technical applications of airfoil sensors regarding incipient separation detection.
文摘During earlier research on shock wave/boundary layer interaction control, the effect of air humidity flow separation has been observed. This has inspired a more detailed study on the effect of air humidity on shock induced incipient separation and on the involved involved processes. The phenomenon has a twofold nature. In supersonic flow, the condensation of humidity causes flow retardation due to heat addition. The consequent weakening of the shock wave reduces the tendency towards separation. On the other hand, the incipient separation is postponed at the same Mach numbers of interaction.
