The static instability of the front-free-aft-fixed rectangular elastic plate in the supersonic uniform air-stream is studied analytically. The two-dimensional supersonic small perturbation potential theory is used for the aerodynamic force evaluation. The aeroelastic divergence speed and the divergence mode are obtained by the analysis. And the piston theory is used also for the aerodynamic force evaluation. The divergence speed based on the small perturbation potential theory is coincident with the one based on the 2nd order piston theory, when the flow Mach number is higher than 3.
The conventional optimization methods were based on a deterministic approach, since their purpose is to find out an exact solution. However, these methods have initial condition dependence and risk of falling into local solution. In this paper, we propose a new optimization method based on a concept of path integral method used in quantum mechanics. The method obtains a solutions as an expected value (stochastic average) using a stochastic process. The advantages of this method are not to be affected by initial conditions and not to need techniques based on experiences. We applied the new optimization method to a design of the hang glider. In this problem, not only the hang glider design but also its flight trajectory were optimized. The numerical calculation results showed that the method has a sufficient performance.
Effects of a curved trailing edge on growth of a compressible “single” shear layer are investigated experimentally. The results are directly compared with those for a compressible “double” shear layer. Mach numbers of the high speed and low speed air streams are 1.78 and 0.29, respectively. The convective Mach number is 0.62. Several types of sine-curved trailing edges are used to induce streamwise vortices into the shear layer. The wavelength of the sine curve is varied widely. It is shown that spanwise vortices due to the primary instability are much more obscure and the spacing varies widely, when compared with those for the compressible double shear layer. And it is shown that, by use of the curved trailing edge, streamwise vortices are induced into the flow. By use of the curved trailing edge, the growth rate of the compressible single shear layer slightly increases. However, when compared with the compressible double shear layer, the increase in the growth rate is much smaller. It is shown that the curved trailing edge is effective for mixing enhancement only when it is used for a compressible double shear layer.
Quick initiation of a detonation wave in a combustion chamber is important to realize high-performance pulse detonation engine. A possible method is to generate a detonation wave in a pre-detonator and release the detonation wave into the chamber. In this paper, a reflecting board is installed in the combustion chamber near the pre-detonator exit where the tube diameter expands abruptly. It prevents the detonation wave from disappearing at the expanding region near the tube exit. The re-initiation mechanisms of a detonation wave near the reflecting board were observed by using the soot film method. Main results obtained in this study are in the followings: Re-initiation of a detonation wave due to the Mach reflection of a shock wave is observed on the surface of the reflecting board and the propagation promoting effect is observed. The effectiveness of the reflecting board is a strong function of the clearance between the pre-detonator exit and the reflecting board, and the promotion effect sharply decreases with increasing the clearance beyond the distance, in which the incident planar detonation wave maintains. By equipping with a reflective board with a suitable clearance, the critical cell size increases by 2 or 3 times.
This paper describes 3-dimensional microgravity experiments of a new docking mechanism for nano-satellite at Japan Microgravity Center (JAMIC). The proposed docking sequence is divided between approaching/grasping phase and guiding phase. In the approaching/grasping phase, the docking mechanism grasps the nano-satellite even though the nano-satellite has some control errors in a docking space. In the guiding phase, the docking mechanism guides the nano-satellite to a docking port while adjusting its attitude in order to transfer electrical power and fuel to the nano-satellite. We design and fabricate an experimental model of the docking mechanism which has the grasping and guiding functions for each phase. The objective of the experiments is to verify the grasping function because 3-dimensional microgravity environment is very important in the approaching/grasping phase. In this paper, we introduce the docking mechanism and the daughtership satellite model and explain the microgravity experimental setup and its results.
The authors develop the space Gas Hollow Tungsten Arc (GHTA) welding which can be performed in a vacuum, since 1993. In order to establish the space welding technologies necessary for the space development, we are also developing the space Diode Laser (DL) welding process in which the welding principle is completely different from the space GHTA welding. The paper describes the welding results by the perpendicular irradiation and oblique irradiation of the laser light in a vacuum. The DL welding experiments using the stainless steel clarified the melting characteristics and the evaporating phenomena in molten metal. And also, it has been clarified that the mass of the metal vapor during welding increases with the reduction of the environmental pressure and the radiation distribution of evaporation metal follows the cosine law.
Detailed magneto-hydrodynamic (MHD) simulations of plasma flows in an inductively coupled plasma (ICP) heater are performed with air as working gas. The plasma flows are numerically solved by axisymmetric Navier-Stokes equations coupled with Park’s two-temperature models and Dunn-Kang’s chemical kinetic models to take into account thermal and chemical non-equilibrium, while induction heating in plasmas is incorporated by solving time-averaged MHD induction equations. Computations are done by changing operating conditions such as input power and background pressure to examine how plasma properties and wall heat fluxes inside discharge chamber depend on these parameters. Numerical results are compared with those of spectroscopic measurement. Good agreement is obtained in downstream region where the flow is in local thermal equilibrium, however, discrepancy of electronic temperature between the simulation and the experiment is found in the discharge chamber where Joule heating is significant.