For laser propulsion systems, it is important to analyze the mechanism of Laser-Supported Shock Waves, which are caused by laser absorption. The main absorption mechanism is Inverse Bremsstrahlung: The laser energy is transformed into the kinetic energy of free electrons by photon absorption during electron-ion/neutral collision, which is re-distributed among heavy particles through collisions. In this paper, we numerically simulate a room-temperature Argon gas which absorbs CO2 gasdynamic laser, using a 2-Temperature model. As a numerical method, we have used Harten-Yee non-MUSCL modified-flux-type TVD scheme in which real gas effects are considered. Detailed discussions are given on the mechanism of Laser-Supported Shock Wave propagation.
This paper presents an experimental investigation of characteristics of the two kinds of wall jets issuing from a rectangular orifice with an aspect ratio of 5. One is the jet with a flat plate set along the long side of the exit (long side wall jet), and the other along the short side of the exit (short side wall jet). Measured results include mean velocities, intensities of streamwise turbulence and visualization of jet flow and the surface flow on the flat plate. The following results are obtained. The maximum mean velocities on the symmetric plane decay similarly as the free jet at the downstream region. In the case of the long side wall jet, the intermediate region between the potential core region and the downstream region appears longer than the others and the spread is strongly restricted near the wall. The saddlebacked mean velocity profiles are observed also for both of the wall jets. The visualizations of the flow by the smoke of dry-ice are consistent with the measured results, and the reattachments following the separation at the exit are confirmed on the plate by the oil-film method.
This paper is an important supplement of the previous one, titled as “A systematic computation scheme for PAR-WIG cruising design point.” The motive is one point—upper limit of aspect ratio of WIG main wing on which sufficient PAR effect can appear at take-off. Previously this fact was described only qualitatively without any FORTRAN computation, and thus aspect ratio of 6.0 was recommended somewhat arbitrarily. The main purpose of this paper is to clarify this point. Accompanying this, some other requirements on geometry of main wing of WIG are obtained.
The authors have proposed the Coordinated Control of a Satellite-Mounted Manipulator with Compensation for Inertial Parameter Variations in the previous paper. In this method, disturbances are absorbed by using feedforward control based on estimation of the manipulator angular momentum, and further errors are removed by using feedback control with gains that change according to the inertial parameter variations of the system. In this paper, the validity and usefulness of the proposed scheme are verified through computer simulation results. The proposed method is also compared with other types of control approaches, including feedforward control using exact calculation of nonlinear terms, feedforward using exact calculation of the angular momentum, and feedback control using fixed or bariable gains. In these analysis, a three-dimensional space robot model is used, so that coupling between roll, pitch, and yaw axes can also be considered.
Air intake is one of the most important components for an airbreathing propulsion system of supersonic and hypersonic vehicles. Air intake can be evaluated by air mass capture ratio and total pressure recovery ratio. In higher Mach number flight condition, larger total pressure losses occurs in the compression processes of air intake and reduces the propulsion performance. By utilizing the precompression coming from oblique shocks generated underneath vehicle forebody, a part of functions loaded in air intake can be substituted by the forebody precompression, thereby overall propulsive performance is able to be improved effectively. In the present paper, the precompression effects given by nose shape of forebody and geometrical arrangement of air intake underneath fuselage were analyzed by CFD calculation using 3-dimensional compressible Navier-Stokes equations.
A multiplexer system which is useful for shock wave experiments has been developed. It transmits plural input signals sequentially to a single output channel. The channel switching is done after, by a preset duration time, being triggered by each relevant input signal. The duration between successive two triggers is not preset but depends totally on characteristics of the input signals. With this system, properties behind a propagating shock wave or a moving projectile can be efficiently tracked and recorded.