Effects of the acoustic disturbance on the 2D mixing layer in Mach 1.78 air flow were investigated. Subsonic gas was injected parallel to the main air flow. Acoustic wave generated by a cavity impinged on the initial mixing layer. When air was injected, it caused large scale structures in the mixing layer, which resulted in the mixing zone expansion. In this case, antisymmetry of the pressure distribution in the mixing layer was observed. According to the linear stability theory, the antisymmetric mode was much more unstable than the symmetric mode. The effects could not be observed when helium, whose density was lower than air, was injected.
The mechanism for two types of turn maneuver of a paraglider is made clear by investigating the lateral responses coupled with the longitudinal motion. One of them is the turn initiated by pulling down one of the side control lines that generates the directional angular velocity and sideslip which produce the rolling moment and the bank angle. The other is the turn due to the lateral movement of pilot's body that generates the rolling moment causing to produce the bank angle. Then the rolling angular velocity produces the directional angular velocity due to the proverse yawing moment of canopy. It was confirmed that, during a steady turn, the centrifugal forces acting on the virtual mass of canopy and body were important factors to balance the rolling moment due to the directional angular velocity.
It is well-known as the coning effect that even the motion around an axis with no angular rate results in the residual rotation when it resumes to the original orientation. However there has been little investigation concerning the residual rotation when the motion is not closed and is not resumed to the original orientation. A definition of rotation angle is proposed in this paper and the method of calculation of the rotation angle is shown. The attitude reference system of one-degree-of-freedom platform type was developed by making use of the rotation angle defined here and two parameters showing the orientation of the rotational axis. The attitude reference system onboard M-rocket worked well.
The QF-104 is a remotely-piloted full-scale drone developed from F-104, which is excellent in the speed performance. Its development program began in 1992 with all the mission by JASDF being completed in March 1997. The drone is operated from the fixed-type ground cockpit using a front view by TV. It has 150msec lag in control. TV camera has limited view angle of 46° in azimuth, 35° in elevation. Those generated difficulties in controlling the aircraft, especially in landing. Several devices were created to cope with the problems, as follows, Landing guidance symbols by vectoring capabilities of the tracking antennas show the deviation from the proper approach-path on the TV screen. Deflection command control laws with heading/wings-level hold mode are proved effective in smooth landing. Yaw string in the nose radome, AOA tone indication, touch down information, and 35 feet over-runway signal are also proved effective.
The flow around a circular cylinder rotating near the critical Reynolds number was investigated by means of the flow visualization in a low speed wind tunnel. The separation line of boundary layer on the surface of a rotating cylinder shows the sinusoidal pattern in the spanwise direction because the vortical motion occurs around the cylinder by the centrifugal instability. At the lower rotational speed than the critical spin parameter where the lift coefficient has a maximum value, the induced flow by the centrifugal instability was clearly observed in the subcritical region, while it could not be observed in the supercritical region. At the higher rotational speed, it could be observed in both regions. In the subcritical region, the rotational speed which corresponds to the critical spin parameter increases gradually when the Reynolds number decreases from the critical Reynolds number. In the supercritical region, it increases rapidly when the Reynolds number increases from the critical Reynolds number. The effect of the centrifugal instability on the transition of the boundary layer on a rotating cylinder appears remarkably in the subcritical region by comparison with the case in the supercritical region.
The nonequilibrium condensation generating around the 2-D and 3-D wings in moist air, so-called 'Vapor Trail, ' is numerically investigated. The fundamental equations composed of the compressible Navier-Stokes equations and tho model equations for the phase change based on the classical condensation theory are solved using the fourth-order accurate compact MUSCL TVD scheme and the second-order Runge-Kutta scheme. As numerical examples, the 2-D transonic viscous flows around the RAE 2822 wing in moist air are calculated changing the relative humidity and the calculated results are compared with those in dry air and the experiment. Also the 3-D flows around the ONERA M 6 wing in moist air are preliminary calculated.
Laminar-to-turbulent transition phenomena over an ablating reentry vehicle has been analyticalty investigated. A two-equation turbnience model (k-ε model) was used with Reynolds averaged Navier-Stokes equations to reproduce the boundary flow transition. Low Reynolds number effect was taken into account by emgloying the Chien's modification. The turbulence induced by turbulent-gas-injection from the ablator surface was multiplied in a boundary layer, and the resulting transition point Reynolds number was 3×104 at the surface mass injection rate of 80g/smsm2.