In this paper, we describe shape optimization of a split-tip winglet (STW) model for the TRA2012A commercial jet aircraft model. The STW configuration is expressed by attaching a small wing under the main winglet. The onboard fuel weight, main wing structure weight and the sum of these weights are objective functions, and are minimized respectively in a fixed aircraft operating range for the present optimization. The onboard fuel weight and main wing structure weight are respectively estimated from the aerodynamic drag obtained using computational fluid dynamics simulations and from an estimation formula based on aerodynamic force acting on the main wing. A Kriging response surface model approach is used as the optimization method. Finally, non-dominated optimal designs obtained using this optimization method are investigated in detail based on the variation in aerodynamic drag and the main wing structure weight. In the STW design having minimum total weight, a reduction in onboard fuel weight and increase in main wing structure weight are observed, and it is found that the reduction in onboard fuel weight per unit volume of STW is the largest.
Downwash effect is the interaction between rotor wake and a launched rocket. Since the effect alters the initial motion of the rocket, a comprehensive analysis of the effect is crucial in predicting the entire trajectory and range of the rocket. In addition, external winds affect the trajectory and range as the winds alter the downwash effect. Because the downwash affected ranges do not appear to be investigated sufficiently, this study aims to reveal the trajectory and range variance characteristics focusing on the downwash effect and external winds. Using an actuator model and six-degrees-of-freedom analysis, trajectories of the rocket due to the downwash effect are described. The range variance characteristics of an unguided rocket are investigated for a 3,000-lb class helicopter, and the rotor flow field database is analyzed using the CFD method while considering external wind effects. It is concluded that the effective angle of attack of the rocket in the rotor wake region varies along the wind direction, and the final reach range also changes accordingly. In particular, the range increased significantly when the rear wind is blown out. However, the range of the rocket is constant after a specified wind speed due to rocket acceleration.
A morphing wing can deform its geometrical shape seamlessly and continuously to improve aerodynamic performance. In our previous study, a multi-layered compliant mechanism composed of stacked compliant mechanisms was proposed as the internal structure of the morphing flap to improve the design flexibility of the deformation shape. Each layer has an independent structural configuration that can be supported under an independently applied load. By connecting layers throughout the wing skin, the multi-layered compliant mechanism is worked as a single morphing flap. This study expands the design flexibility of the multi-layered compliant flap to achieve different morphing shapes by considering multiple flight conditions. For this purpose, load cases with different actuation forces according to the flight conditions are introduced and the design problem is formulated using a multiobjective optimization problem. Through numerical examples, several Pareto configurations of the multi-layered flap are demonstrated to facilitate deformation to yield different desired morphing shapes to maximize the lift-to-drag ratio or maximum lift coefficient. In addition, the trade-off between the two objective shapes is examined to investigate the effects on the values of these functions and the resulting configurations.
The present paper is the first report of an experimental study on the energy efficiencies in the millimeter wave power transfer to an autonomously-controlled micro aerial vehicle (MAV). A tight beam of millimeter wave at 28 GHz was transmitted vertically upward, and a quad-rotor type MAV was autonomously controlled using the iterative feedback tuning method to hover over the beam and receive the millimeter wave power. The maximum value of the receiver efficiency was (1±2) × 10–3 and its duty ratio was 0.29±0.08, for which the distance between the MAV and the millimeter wave transmitter was 800 mm. The energy loss and the low duty ratio were both due mostly to the loss in the capture efficiency due to the location scattering of the MAV.