Passive damping augmentation is one of attractive methods for vibration suppression to various kinds of structures because it is definitely stable and generally simple. The system using thin film with viscous adhesive indicated a remarkable effect to the vibration suppression in the practical application to a satellite. To investigate its damping characteristic, several kinds of experiments have been performed. The results show that the non-linear behavior cause of non-Newtonian flow between shear load and shear deformation velocity in the viscous lamina of the thin film contributes to the damping capability. A mathematical model which consists of spring elements as film and friction elements as viscous lamina has been proposed from experiments. The simulational results with this present model are in good agreement with experimental ones.
A three-dimensional particle-based membrane model, which is used to predict the shape of the membrane aeroshell with large deformation due to the aerodynamic force acting on the body, is developed. In this model, the elastic forces consisting of the tensile force, shear force, and bending force are considered as well as the aerodynamic force. Thanks to the particle-based formulation, the present model is less complicated and can be solved with small computation time. To check the validity of the model, various problems on the membrane including the Poisson effect, large deformation, buckling and wrinkling are solved and the results are in a good agreement with the analytical solutions. At last, the present method is applied to the re-entry capsule concept with a flare-type membrane aeroshell. Coupled analyses with the Newtonian flow approximation show that the flare-type membrane aeroshell is deformed to concave shape and some longitudinal wrinkles are generated by the aerodynamic force.
An experimental study on the improvement of aerodynamic characteristics of basic configuration for winged vehicles with lateral blowing in subsonic flow has been conducted. Wing planform is 75º/45º double delta wing whose cross section is modified NACA0010. Lateral blowing is realized by injecting a pair of sonic jets parallel to the trailing edge of the wing. The experiments have been conducted in the transonic wind tunnel of JAXA (Japan Aerospace Exploration Agency) under the testing condition of free-stream Mach number M∞=0.3, Reynolds number Re=2.14×106, angle of attack α=-15–40º and jet momentum coefficient Cμ=0.0166,0.0295 and 0.0398. The results show that the lift coefficient CL and lift-to-drag ratio L/D are increased by lateral blowing over the wide range of angle of attack. The results suggest that lateral blowing can be useful for the improvement of aerodynamic characteristics of basic configuration for winged vehicles in subsonic flow.
This study focuses on the formation mechanism of para-foil canopy. Three types of model wing, which represent each cell of para-foil canopy (a rigid wing with air intake, an inflatable wing and a cassette model) were prepared to explore the effects of air intake on inflatable wing formation in wind tunnel experiments. The flow fields both outside and inside of the wings were investigated, together with the process that the flexible wing inflates to form a wing. It was found that the robust nature of canopy is derived from the concaving deformation of the leading edge at small angles of attack, and the enhanced outward suction pressure acting on the leading edge, which are caused by the flexibility of the wing as well as the pressure of air intake in sacrifice of increased drag coefficient.
The present paper reports the influences of the quality of grid and the sensitivity of slope limiter on the convergence to steady solutions of the Euler equations on solution-adaptive unstructured grids obtained by Rivara’s bisection algorithm. The numerical experiments for two-dimensional supersonic flows over a wedge and a circular cylinder have been conducted to examine the effects of grid quality and limiter’s sensitivity on the convergence by using an implicit unstructured-grid flow solver with Venkatakrishnan’s slope limiter and the GMRES (generalized minimum residual) method. The results reveal that the oscillations of solution induced by the slope limiter on low aspect-ratio grids, which were generated by the solution adaptation, inhibit the convergence to steady state and that the smoothing of solution-adapted grids as well as the use of less sensitive limiters effectively reduces the oscillations of solution.
Since attitude control is not working, most space debris is rotating. For this reason, in capture of the space debris, there is a complicated dynamic interaction among a target, a servicing vehicle, and its robot arm, and there is a possibility that big load may occur. This paper proposes a new capture strategy of the space debris that utilizes joint impedance control and joint virtual depth control to the arm for capture. The validity of the proposed strategy is verified by some simulations and experiments.
We have proposed an ultra-light reflector antenna whose aperture diameter is larger than 20m and whose weight is less than 80kg. Our target is an areal density of 0.25kg/m2 or less. To realize this new reflector antenna, we propose a geodesic cable network system supported by a tendon-reinforced structure. To confirm this concept, we fabricated and tested a scale model of the support structure. The scale model, which is around 3m in diameter and deployable, consists of spoke-wise framing, tendon cables and dummy tension cables. Static load responses were measured by using strain gauges and load cells. Deformation modes were also captured by a videogrametry system. We can conclude that the tendon-reinforced deployable frame structure can support six times the tension possible with the bare structure, and analytical results show good agreement with experimental results by considering the initial imperfection in the scale model.