An experimental study has been conducted to investigate the effectiveness of film cooling in hypersonic, high-enthalpy flows. Both air and nitrogen are used for a test gas and a coolant gas is helium. Injection mass fluxes are varied by changing total pressure of the coolant gas. The half-surface of a flat plate model with a blunt nose is coated with the thin film of silicon dioxide to obtain the dependence of heat fluxes by catalytic recombination effects. Heat fluxes are calculated by surface temperatures measured by coaxial thermocouples. In the case of dissociated air free stream, catalytic effects are observed in our wind tunnel. Experimental results show that thermal protection by film cooling is effective in chemically reactive flows. Non-dimensional heat fluxes and cooling lengths in the dissociated free stream are at the same level as in the nitrogen flows. With film cooling, heat fluxes on the non-coated surface are nearly as same as coated surface regardless of the wall catalysis.
Pseudolites have potential to enhance the performance of GNSS, and research and developments have been conducted in several aspects. If pseudolites were mounted on aircrafts, its GNSS-like signal would be stable augmentations that would improve the accuracy, availability, and integrity of GNSS-based positioning systems. A pseudolite installed on a stratospheric airship, or a high-altitude unmanned aerial vehicle, could be used as a continuous GNSS augmentation, while a pseudolite on a helicopter could be used as a temporal navigation aid for emergency vehicles in hazardous area. In order to establish fundamental technologies for such a system, the augmentation tests using a GPS pseudolite installed on a helicopter were conducted. The position of the pseudolite antenna underneath the helicopter, which is analogous to the GPS ‘precise ephemeris’, was successfully determined with a few centimeters accuracy by inverted GPS method. Also, the results demonstrate the efficacy of integrating the pseudolite signal with GPS.
This paper presents a basic study on the characteristics of capillary wave propagation on a water ligament surface. The capillary wave plays an important role in de-stabilizing ligaments created by the turbulent motion of liquid jet. The ligament end contracts due to capillary force and emanates surface waves. The analysis is based on 2D numerical simulation and linear wave analysis, and reveals the basic characteristics such as contraction speed, wave speed and the associated flow field structures. The phenomenon can be parameterized by the Ohnesorge number, and the numerical results are in good agreement with the linear analysis. The higher pressure cases, where the Ohnesorge number is high, will be investigated in the next step.
An experimental study on aerodynamic effect of lateral blowing for flat delta wings with three different planforms and a rectangular wing has been conducted. Lateral blowing is realized by injecting a pair of jets parallel to the trailing edge of the wing. Experiments have been conducted in the wind tunnel of Kyushu University under a test condition of free-stream velocity V∞=20m/s, Reynolds number Re=2.6×105 and 5.3×105, and jet momentum coefficient Cμ=0.07. Results show that increase of lift due to lateral blowing in all wing types is obtained over a wide range of angle of attack. The lift-increase ratio of flat delta wing with small sweepback angle and the rectangular wing is larger than that of the other wings in high angle of attack region. We could investigate aerodynamic effects of lateral blowing on the flat delta wings with various planforms and rectangular wing.
An experimental study on aerodynamic effect of RLVs (Reusable Launch Vehicles) due to fuselage cross sections has been conducted in subsonic flow. Three fuselage models and two wing-body models have been considered. Fuselage models have a circular, a square and a triangular cross section. Wing-body models have a square and a triangular cross section with wings. Experiments have been conducted under test conditions of free-stream Mach number M∞=0.3 and Reynolds number Re=3.2×106. Aerodynamic forces are measured and flow fields are visualized by smoke-wire technique and oil-flow technique. Results show that fuselage cross sections have much effect on whole aerodynamic characteristics, the fuselage model with a triangular cross section has higher lift coefficient in high angle of attack region than that of the other fuselage models and the wing-body model with a triangular fuselage cross section does not stall till high angle of attack region compared with the “Square” fuselage wing-body model.
The adoption of three types of nozzle contours, the ramp nozzle, symmetric ramp nozzle, and symmetric swept-ramp nozzle, in chemical oxygen-iodine lasers with supersonic ejector-nozzle banks is examined by simulating the mixing and reacting flow fields numerically. The compressible Navier-Stokes equations with a detailed chemical kinetic model are solved using a full-implicit finite volume method. The numerical results show that streamwise vortices induced downstream of the base region of the nozzle array are enhanced with decreasing the length ls of diverging region in I2 nozzle. However, the optimum ls which results in a high small signal gain coefficient exists for each nozzle contour, since the mixing depends also on the size and location of the streamwise vortex. Therefore, the symmetric swept-ramp nozzle which produces strong streamwise vortices even with rather large ls is most preferable among the proposed nozzle contours. The pitot pressure in the mixing region obtained in the present calculation is approximately 10kPa which is ten times higher than that of conventional supersonic flow chemical oxygen-iodine lasers.
The work described here relates to the method measuring the boundary layer transition at “lowspeed” and “atmospheric” wind tunnel for an aircraft model made by metal. The objective of the research is to improve the test technique and to know a precise procedure about transition measurements, especially for an aircraft model at such type of typical wind tunnel. At JAXA 6.5m×5.5m Lowspeed Wind Tunnel (LWT1), the boundary layer growing on the left-wing of the ONERA-Model was investigated using two kinds of the visualizing methods, namely Temperature-Sensitive Liquid Crystal Film and Infrared Ray (IR) Camera. Throughout the experiment, a lot of knowledge was obtained. Comparison of the results from two devices showed that IR camera has possibility to be more effective using after cooling of model surface.
In this paper, a concept of a new variable-geometry aerodynamics device, which is designated “Multiple-Row-Disk (MRD) device,” is introduced. The MRD device divides large separation region around the shaft of an aerospike into several small cavity flows with multiple disks arranged on the shaft. Experimental studies on aerodynamic characteristics of conical nose with axisymmetric cavities were conducted in order to evaluate a feasibility and a fundamental characteristics of the MRD device. It was found that the MRD device could improve not only drag characteristics compared to the conventional aerospikes, but also static longitudinal stability characteristics compared to the conical nose.