Some investigators of WIG, Wing-in-Ground effect vehicles, suppose that high values of lift coefficient (CL) for WIG's are desirable at the cruising condition; it seems to result from the old term “Ram-Wing.” This paper treats high-speed large-scale WIG's only for transportation such as Orlyonok. It is shown that as higher cruising speed as possible is required for higher transportation efficiency and so considerable width of CL values are necessary. Hence it is an important problem how the lower value of CL may be allowable without deteriorating the operational efficiency. It is found that CL of nearly 0.6 are acceptable and cruising speed of 480km/h is expected with effective aspect ratio of 10-12. Thus lower camber shapes of airfoil, which give the center-of-pressure of nearly 25-33% chord positions, may be usable against the image of “ram-wing.” It would bring an additional considerable merit that many troublesome problems of trim, stability and control may be solved much more easily.
Finite element analysis of 3-dimensional large rotation problem of a beam has been possible by means of nonlinear beam model by J. C. Simo, L. Vu-Quoc. Their beam model is regarded as geometrically exact, and described by a configulation manifold which involves the rotation group. In result, the tangent stiffness matrix becomes non-symmetric away from equilibrium. But I showed that the tangent stiffness of semitangential rotation ΔδΠs became symmetric, and by the comparison of the analyses of the fundamental problems with Miyazaki, ABAQUS and Nour-Omid, B. and Rankin, C. C., it was proved that the symmetric tangent stiffness was valid. By the way, the beam model is assumed large rotation and small strain. Then in the previous report, I showed the geometric stiffness of large strain by the variation of deformation gradiant tensor before rigid body rotation. But, that formulation was total lagrangian formulation parametrized by the coordinate of the center line of the reference configulation. Now, I will show the large strain beam model of updated lagrangian formulation parametrized by the coordinate of the center line of the current configulation.
A design method of nozzle for ionized gas, which is used for arc heated wind tunnel, has been studied by coupling a nonequilibrium computational fluid dynamics code with the characteristic method, where argon gas is used for the simplicity of analysis. The method to analyze the boundary layer with thermally nonequilibrium flow is also presented. The effect of the nonequilibrium characteristics is represented as the equivalent specific heat ratio, where iteration is required to calculate it. The final flow contours show that the distribution of Mach number is uniform at the nozzle exit, where the nozzle exit Mach number is set at 5. Thus the high enthalpy nozzle design method has been established.
The aircraft is a system consisting of a pilot and an aircraft. To understand the system, the pilot dynamics needs to be known. This paper proposes a method to identify the pilot dynamics including feedback structures. The method utilizes the autoregressive scheme, and makes a singular value analysis of the closed-loop transfer function matrix in addition to a correlation analysis of the innovations. By treating the latera-ldirectional flight path control of an aircraft, it is shown that the proposed method clearly distinguishes between two assumed feedback structures, and the pilot dynamics is properly identified in the correctly chosen feedback structure.
Results of fixed-base simulator tests for augmented aircraft are presented in order to distinguish characteristics of a rate-command system from those of an attitude command system. Regulating aircraft states is requested by manual control of a subject pilot with a major concern for pitch attitude, under various combi nations of simulated turbulence intensities and bandwidths. Pilot dynamics in the closed loop is identified by applying the autoregressive model analysis using the measured data. The obtained loop transfer functions are compared in the light of stability margins and crossover frequency as well as of bandwidths and the equivalent time delay. It is concluded that the rate-command system is inferior in disturbance regulation tasks to the attitude-command system in that it shows less robustness beyond the frequencies defining the pilotaircraft bandwidth.
In order to better understand the von Kármán vortex shedding on the basis of the concept of absolute instability, the vortex shedding from a blunt-ended flat-plate is examined experimentally through controlling the wake development. The stability analysis is also made for the velocity distributions in the near wake region to obtain their local instability characteristics. When the vortex shedding is controlled by another flat-plate in the wake, the shedding frequency is remarkedly changed. Such change in frequency is found to be closely related to the change in the absolute instability characteristics of the wake velocity distributions immediately behind the plate base.
Silicon-nitride (Si3N4) ball bearings were tested at 500°C in a vacuum. Excellent tribological performance was obtained for more than 1.5×108 revolutions (about 4200 hours) by lubricating the bearings with both a sputtered molybdenum disulfide film on balls and races and a transfer film formed from a hot-pressed self-lubricating composite retainer. A 650°C test is under way, in which the bearings have been showing low and stable frictional torque up to 500 hours of operation.