Wing-tip vortices in formation flight

In order to better understand influences of wing-tip vortices of leading wing on the aerodynamics of trailing wing in formation flight of two wings, behaviors and interactions of wing-tip vortices are examined experimentally.  Both the wings which consist of a NACA23012 airfoil section and a rectangular plan-form with aspect ratio of 5 are set in the same horizontal plane, 2.5 times the airfoil chord apart in the streamwise direction. The leading wing is fixed at an angle of attack 8°.  In such a configuration, the lift to drag ratio is found to increase by 25% when the two wings are overlapped with each other by 2.5-5% of the wing span in the spanwise direction.  Flow visualization and PIV measurements show that the wing-tip vortices of both the wings interact most closely to form a pair of counter-rotating vortices in such overlap conditions.  It is also shown that the circulation of wing-tip vortices of trailing wing is markedly affected by those of the leading wing.

Flow visualization of a wing boundary
layer of human-powered plane

Influences of surface waviness of the wing of human-powered aircraft on the boundary-layer transition and separation are investigated experimentally at a Reynolds number Re=3.7×10⁵.  We consider a wing of human-powered aircraft constructed by full- and half-chord rib structures with film sheet, whose surface is wavy in the spanwise direction with the maximum amplitude of 6% of the airfoil thickness.  Flow visualization shows that the transition occurs around the mid-chord of the wing at the angle of attack of flight condition 6° both for the smooth- and wavy-surface models.  It is also observed that the location of separation-bubble varies periodically in the spanwise direction in correspondence with the periodic array of rib structures at low angles of attack.  It is also found that the stall is delayed slightly by the surface waviness.  In spite of remarkable difference in the separation bubble, however, the lift and drag are little affected by the waviness except around the stall angle.

The Human-powered airplane (HPA) is popular in Japanese because of the Birdman Rally. Most HPA crashed immediately after the start in old times. Recently, most HPA fly by 100m or more. But the crash of HPA happens frequently due to the control mistake. Most human-powered airplanes should control only with the tail because there is no aileron. HPA equips with “all flying tail”, it is different from a usual airplane. Therefore, the control of HPA is very difficult. In the improvement of the control performance of HPA, it is important to understand the operation of the tail and the response of the aerodynamic force. So I study on the response of wing aerodynamics to sudden changes in the angle of attack.

ULP - MX2 Sprint

[under construction]