A flight speed control for the conflict avoidance in a self-separated high density air corridor is discussed. The conflict often occurs in a congested situation due to a large flight speed difference between a pair of aircraft in overtaking. To resolve such a conflict situation, flight speed control to reduce the relative velocity is newly introduced in this study. This control strategy leads the aircraft that are expected to cause the conflict to accelerate/decelerate in order to reduce the flight speed difference for a short while. Its effectiveness is investigated through numerical simulations to prove that the presented control strategy has achieved the conflict free corridor traffic.
Much attention is paid to lattice structures as effective structural elements for aerospace applications. Lattice structure has periodic system made of discrete beam-like ribs. Under compressive force, ribs may deform in the lattice plane as well as out of plane and cause local rotation in the unit cell. Though this local rotation can make a difference between the buckling modes of lattice and homogeneous shell structures, it has not been considered properly in the previous lattice design. This study focuses on the local rotation that is unique to lattice structures and clarifies its effects on buckling modes using finite element method (FEM). The buckling analysis of unit cell structure shows qualitative and quantitative correspondence with experimental and analytical results. This analytical model shows that the buckling load of whole structure with design values derived by the previous study which neglects local rotation is far below the target load. It clearly shows the defect of the previously proposed design procedure. Moreover, additional analyses with different design values provide unexpected buckling modes in which local rotation cannot be neglected. This suggests the importance of considering the effects of local rotation on buckling modes in the design phase.
This paper describes the development and the wind tunnel test of a variable geometry morphing airfoil using corrugated structures. Feasibility of a morphing wing with corrugated flexible seamless flap-like structure is verified by the finite element analysis, and a prototype is manufactured using carbon fiber reinforced plastics. For the actuation system, two servomotors are installed inside the prototype wing to control the airfoil shape by the chord-wise tension of the connected wires. Successful actuation of the prototype wing is demonstrated under the air speed up to 30m/s in the wind tunnel test. Basic aerodynamic properties are also evaluated in comparison to traditional airfoil with a hinged control surface. Lift increase of variable corrugated wing is recognized when the flap angle increases.
Effects of a slit injection (SI) on exhaust noise from a rectangular hypersonic nozzle were investigated experimentally. In the Japan Aerospace Exploration Agency (JAXA), the pre-cooled turbojet (PCTJ) engine specified for a hypersonic transport is under development. In this study, a 1/100-scaled model of the rectangular hypersonic nozzle for the PCTJ is manufactured. The main jet (MJ) is injected to the atmosphere through the nozzle. The total pressure of the MJ was set at the takeoff condition of the vehicle. From slit shaped converging nozzles mounted at the end of the ramp, air is injected to the MJ. The sound pressure level (SPL) around the nozzle was measured with microphones. Using the SI, especially in the ramp direction, the SPL was decreased by 1 to 2dB at wide frequencies up to 50kHz. At the same time, the Overall SPL (OASPL) decreased monotonously with the increase in the momentum ratio of the SI and the MJ. It is considered that the governing parameter of the SI is the momentum ratio. The growth rate of the shear layer was estimated from Pitot pressure distribution. It is implied that the shear layer growth rate is linked to the acoustic radiation.