Yaokun Wang

Yaw Effects on Vortex Flow over a Chined Fuselage at High Angle of Attack

Particle image velocimetry (PIV) experiment technology and surface pressure measurement have been used to investigate yaw effects on vortex flow over a chined fuselage with Reynolds number of 1.87 × 105 at angle of attack α = 50° and sideslip angle β = 4°. Under condition of no sideslip, there are two symmetric leeward vortices with strong intensity. Due to the yaw‐induced corssflow, the upwind vortex is drawn closer to model surface and the downwind vortex is displaced upward and outward, and vorticities of the two vortices decrease in various degree. At the same time, the yawing condition causes the downwind vortex burst at an axial position in front of the upwind vortex. As a result, the suction effect is enhanced on upwind side and reduced on downwind side. A restoring side force forms on forebody, which indicates the chined forebody has static directional stability at high angle of attack.

Effect of canard on the wing rock motion of a chined-body configuration and it's mechanism

By adding canards to the chined-body configuration, its influences on wing rock motion and its mechanism at angle of attack of 30° have been investigated through a series of experiments. Experimental results show that the asymmetric flow over the chined-body configuration, especially the flow over the windward wing during rolling motion, is influenced strongly by the flow over the canard and as a result the wing rock motion of the chined-body configuration can be suppressed finally.

Interference of Double Rotating Shaft Support in Low Speed Wind Tunnel

Support interferences always affect the accuracy of the wind tunnel experimental data. Therefore studying support interference is of significant value in practice. The double rotating shaft support is a novel way of support. In this paper, numerical simulation has been taken to investigate the effect of the double rotating shaft support system on aerodynamic forces and moments of DBM model. It is found that the support system induces the lift coefficient and the drag coefficient to decrease and the pitching moment coefficient to increase. For the parts of the model which are above the wing plane, the lift coefficient and the drag coefficient decrease. And for the parts of the model which are below the wing plane, the lift coefficient and the drag coefficient increase. For the pitching moment coefficient, the influnence is opposite to that of force.

Experimental Investigations of Free‐To‐Roll Motions Induced by Wings and Forebody Complex Flow Under Pitch‐Up Motions

Experiments have been carried out at sub‐critical Reynolds number to investigate wing rock induced by forebody and/or wings complex flow on a 30° swept back non‐slender wings‐slender body‐model for static and dynamic (pitch‐up) cases. Four angle of attack regions have been identified based on the characteristics of FTR motion and associated flow structures at static angles of attack. For the dynamic (pitch‐up) case it has been observed that roll amplitude decreases and lag increases with increase in pitching speed. Decrease in roll amplitude with increase in pitch rate is attributed to low disturbing rolling moment due to weaker interaction between forebody and wing flow components. Forebody asymmetric vortices dominate and control the roll motion of the model in dynamic case when non‐dimensional pitch rate ≥1 × 10−2 and the roll behavior is like a sinusoidal curve. There is almost no contribution to the roll motion from the wings flow at lower angles of attack for high pitch rates.

The Study of Determinacy of Asymmetric Vortices over Slender Body at Post-Critical Reynolds Numbers

An artificial transition technique of setting transition wires on both side of a pointed-ogive cylinder with the nose fineness ratio 3.0 was used to simulate the post-critical Reynolds numbers flow at high incidence in low-speed wind tunnel. The results based on this artificial transition technical indicate that the indeterminacy of asymmetric vortices aroused by nose-tip imperfection resulted from machining tolerance still exists in post-critical Reynolds numbers flow. The indeterminacy of asymmetric vortices can be eliminated by adding the micro-triangle block artificial perturbation with thickness of 0.2mm to the nose-tip, and the artificial perturbation on nose-tip can promote the asymmetric vortices into bistable state at α=50°. When the results of artificial perturbations with various thicknesses are combined, it is indicated that the intensity of artificial perturbation must be considered when it was just used to eliminate the indeterminacy of asymmetric vortices.