Takahiro Ukai

Simultaneous visualization of surface and flow field for a projectile

This paper reports establishment of the simultaneous measurement of the flight attitude and flow field visualization for the near-field pressure measurement experiments in a ballistic range. To measure the flight attitude and flow field visualization for a spherical projectile, the simultaneous visualization method, which is combination of the shadowgraph method and the direct photography, was utilized. It is possible to visualize both the flow field around the projectile and the projectile surface. The angles of pitch, roll and yaw can be calculated from the displacement of line markings on the projectile surface. The image of the projectile by the direct photography is distorted because of the aberration of the optical arrangement, the camera lens and the non-uniform thickness of acrylic windows. Image distortion was calibrated by taking images on actual set-up, so that the accuracy of the angles was improved. In addition, the diffuse reflection light from the projectile surface was confirmed not to influence the flow field visualization. This method is useful for the near-field pressure measurement experiments in a ballistic range. The flight attitude affects the near-field pressure value strongly. Since the near-field pressure with a detailed flight attitude is obtained, its influences can be evaluated using the method which has ability of the flight attitude measurement. In addition, a shock interaction around a projectile can be captured.Graphical Abstract

Incident Shock-Transverse Jet Interactions at Mach 1.9: Effect of Shock Impingement Location

The scramjet engine is an efficient design for high-speed propulsion, requiring injection of fuel into a supersonic flow in a short amount of time. Due to the nature of the flow numerous shock waves exist within the combustor of a scramjet, significantly altering the flow characteristics and performance of the engine as the flow Mach number or attitude is changed. According to Mai et al. [1] the location of impingement of the incident shock, relative to the fuel injection location, has significant impact on the mixing and flame-holding properties. This emphasises the importance of understanding and hence the need for controlling the dynamic interactions that are created. Of course another fertile area where transverse jet injections are studied for their application is the creation of forces and moments for pitch and attitude control [2, 3].

Experimental study of dual injections with a cavity in supersonic flow

The design of supersonic injection systems is a key issue for the development of a supersonic combustion ramjet (scramjet) [1]. Since supersonic flow is present in the combustion chamber of the scramjet, it is difficult to satisfy features which indicate fuel-air mixing and flame stabilisation.

Suspended liquid particle disturbance on laser-induced blast wave and low density distribution

The impurity effect of suspended liquid particles on the laser-induced gas breakdown was experimentally investigated in quiescent gas. The focus of this study is the investigation of the influence of the impurities on the shock wave structure as well as the low density distribution. A 532 nm Nd:YAG laser beam with an 188 mJ/pulse was focused on the chamber filled with suspended liquid particles 0.9 ± 0.63 μm in diameter. Several shock waves are generated by multiple gas breakdowns along the beam path in the breakdown with particles. Four types of shock wave structures can be observed: (1) the dual blast waves with a similar shock radius, (2) the dual blast waves with a large shock radius at the lower breakdown, (3) the dual blast waves with a large shock radius at the upper breakdown, and (4) the triple blast waves. The independent blast waves interact with each other and enhance the shock strength behind the shock front in the lateral direction. The triple blast waves lead to the strongest shock wave in ...

Experimental Investigations of Three-Dimensional Shock-Vortex Loop Interaction: Shock Reflection and Diffraction Phenomena

Estimation of the sonic boom and its effect are necessary to develop supersonic transport vehicles. The typical sonic boom is produced by the shock waves generated from a supersonic transport vehicle cruising at more than the speed of sound. The shock waves pass through the real atmosphere and reach ground level. The sonic boom pressure signatures are affected by atmospheric conditions such as turbulence, humidity, and temperature [1]. These atmospheric conditions cannot be controlled; however, they must be considered. Atmospheric effects have to be well understood because it is extremely important to accurately estimate the sonic boom magnitude at ground level.