An experimental investigation has been carried out on interference effects in vortex-shedding from a heated circular cylinder in the crossflow Reynolds number (Re*=2, 500) subjected to the acoustical vibrations whose SPL is over 130 =dB. Due to acoustic interferences on vortex-shedding, the separation point is slightly shifted downstream around its surface, the laminar-turbulent transition in the separated shear layer is promoted, the shear layer becomes thicker, the vortex-shedding position gets nearer to it, the strength of the vortices is also increased, and its form drag coefficient increases. There is a critical value for the applied sound pressure level over which powerful effects on vortex-shedding is observed. The vortex-shedding frequency fs is a little changed by the applying sound field. The change is remarkable for sound pressure level exceeds a critical value (=130dB) and the cylinder is heated. These phenomena are analogous to the thermoacoustic streaming in the natural convection.
Convergence of lifting surface numerical computations with mode method would be generally deteriorated by kinks, especially on the leading edge, of wing planforms. The intrinsic cure should be brought about by the appropriate mode function (eigensolution) for the kinks, rather than “rounding off” of the kink, although the latter has often readily been used. A new unified formula of eigensolution is developed through results of a series of numerical computations with discrete lifting surface scheme “BIS.” But the parameters appearing in this formula were determined by using the results of previous analytical solutions obtained by other authors, because of their superior accuracy.
Concept of “Autonomous Controller Redesign” is proposed as a new approach to onboard spacecraft control system reconfiguration. In this concept, when some failures occur in control system, “Autonomous Controller Design System” redesigns the control system fully considering given control requirements and constraints. In order for various type requirements and constraints to be taken into account, search-based design procedure is indispensable, but this may cause difficult problem of combinatorial explosion of search space. To solve this problem, knowledge oriented search is utilized, and machine learning is essentially used to acquire such knowledge. Actual computer program has been developed, and its performance is verified by computer simulations. The capability of this system as a reconfiguration tool is also verified by simulations assuming attitude control system with 4 reaction wheels. It is indicated that the new methodology can more flexibly design control systems under the new physical constraints induced by failures.
A 2-dimensional, small high speed cryogenic wind tunnel was constructed at National Defense Academy (N. D. A.) in 1985, using the stainless steels of SUS 304 and SCS 13 as materials of the pressure shell. The features of the cryogenic tunnel and its operation procedures are described. The initial operational tests were intensively performed to refine the general operation method to the optimum for the present tunnel with the original manual control systems. Those tests showed that the original control systems were fairly acceptable, but had to be modified to automatic controls for more precise control of the tunnel flow conditions at cryogenic temperature range and expanding its actual operational envelope.