Shinji Sezaki

Measurements of Capsule Wake Stabilization Times in a Hypersonic Gun Tunnel

The wake stabilization time behind a hypersonic vehicle is very important in experiments focused on the nearwake studies in pulsed facilities at high-enthalpy and high-Mach-number conditions. Observations of such wake structure have been very difficult to obtain, and therefore, the experimental discussion about the stabilization time itself has also been elusive. The wake structure stabilization time was formulated by using dimensional analysis and the present experimental results. The experiments were carried out by observing free shear layers for capsule models similar to the Mars Environmental Survey Pathfinder probe. To visualize the wake structure, an electrical discharge method was used. From these investigations, it was found that the stabilization time of the wake structure was related to the Reynolds number, the model size, and the freestream velocity. A Mach 10 gun tunnel was used in these experiments. Nomenclature A = projected area of model D = capsule maximum body diameter k = proportionality constant Rb = capsule maximum body radius R f = distance between free shear layer and symmetry axis Re =R eynolds number T = stabilization time of wake pattern measured from the beginning of stable uniform flow T0 = stabilization time of wake pattern measured from the beginning of flow obtained by a pulsed facility T1 = elapsed time from the beginning of flow obtained by a pulsed facility T2 = stabilization time of freestream measured from the beginning of flow U = freestream velocity α = constant µ = viscosity coefficient ρ = freestream density

Visualization of Flow Structure Around a Hypersonic Re-entry Capsule Using the Electrical Discharge Method

The spatial flowfield around a model of the re-entry capsule of the Mars Environmental Survey (MESUR) Pathfinder probe afterbody configuration traveling at a speed of Mach 10 was investigated utilizing the electrical discharge method. The shock shape ahead of the capsule was observed using a technique for visualizing 3-D shock shapes, then the streamline following the shock wave was observed utilizing a technique for visualizing streamlines crossing a shock wave. Subsequently, the flowfield behind the capsule was observed by applying a technique for visualizing flow patterns. From these observations, the spatial flow construction including the wake region such as a separation, free shear layer, and rear stagnation location behind the capsule was made clear. These experiments utilizing the electrical discharge method qualitatively demonstrated the spatial flow structure before and behind the hypersonic re-entry capsule, which had been very difficult to visualize. These experiments were carried out by using a pulsed facility of 18 ms duration.

Study on Stabilization Time of Wake Structure Behind Hypersonic Vehicles by Electrical Discharge Method

A stabilization time of a wake structure behind hypersonic vehicles is very important in experiments on the flow structure by using pulsed facilities of high enthalpy or of high Mach number. However, observations themselves of such wake structure have been very difficult, and therefore, the experimental discussion about the stabilization time itself has also been very difficult. In this study the stabilization time of the wake structure was formulated by using the dimensional analysis and the present experimental results. The experiment was carried out by observing separation points and free shear layers just after three re-entry capsule models. To visualize the wake structure, one of techniques called the electrical discharge method was utilized. From these investigations it was found that the stablization time of the wake structure was related to the Reynolds number, the model scale, and the freestream velocity. A hypersonic gun tunnel of Mach 10 was used in this experiment.

Study on Flow Structure around Hypersonic TSTO Launch Vehicle

Flow structures around hypersonic TSTO launch vehicle were investigated by utilizing the electrical discharge method. First, boundary layers near the orbiter surface were observed by a visualization technique of boundary layers. Subsequently, lateral and cross-sectional shock shapes around TSTO launch vehicle were observed by a visualization technique of shock waves. From these results, it was confirmed that a separation shock wave was generated near the orbiter surface. In this study, the visualizations were carried out at Mach 10.

Experimental Study on Flowfield Around Hypersonic Space Plane Utilizing the Electric Discharge Method

This paper described the flowfield around a space plane traveling at the speed of Mach 10. The visualization of the flowfield were carried out utilizing the electric discharge method. The electric discharge method has been invented and developed by the author and others for visualizing three-dimensional hypersonic flowfield phenomena. In this paper the lateral and cross-sectional shock shapes around the space plane were demonstrated.

STUDY ON FLOWFIELD AROUND SPACE PLANE TRAVELING AT MACH 10

The flowfield analysis around a space plane traveling at the speed of Mach 10 was carried out by numerical and experimental methods. Numerical simulation program of hypersonic flow is developed based on FEM (Finite Element Method). Pressure term is partially integrated in an element by applying the weighted residual method, and the hypersonic flowfield around a space plane model including shock wave can be calculated. The simulation results are compared with experimental results obtained by the electric discharge method, which has been invented and developed by the author and others, and good correlation between them was found.