Masatomi Nishio

New method for visualizing three-dimensional shock shapes around hypersonic vehicles using an electrical discharge

This paper describes a new method for visualizing three-dimensional shock shapes around hypersonic vehicles using an electrical discharge. The method is based on the following ideas. When an electrical discharge is generated across a shock wave, the shock wave can be seen as a dark portion in the electrical discharge. The three-dimensional shock shape can be visualized by taking a discharge photograph in the rear direction of the flow. The method was developed to make it possible to visualize wide field shock shapes around vehicles using a single electrical discharge. First, a lateral shock shape over a wedge was visualized to investigate the accuracy of the shock shape obtained by the new method. The visualized result was compared with a schlieren photograph, and it was found that the results of both agreed sufficiently. This proved that the new method is a viable method for visualizing shock shapes. Next, a detached cross-sectional shock shape over a delta wing was successfully visualized. Cross-sectional shock shapes cannot be visualized by such optical systems as the schlieren method. Therefore, it can be concluded that the new method is superior for visualizing three-dimensional shock shapes.

Methods for visualizing hypersonic shock-wave/boundary-layer interaction using electrical discharges

Two methods for visualizing the spatial flowfield of hypersonic shock-wave/boundary-layer interaction were developed by utilizing the radiation of electrical discharges. One method visualizes boundary layers in hypersonic flow, and the other visualizes streamlines near wall surfaces in hypersonic flow. These two methods were applied to the visualization of hypersonic shock-wave/boundary-layer interaction, and the results confirmed that the two methods are useful for visualizing the spatial flowfield of hypersonic shock-wave/boundary-layer interaction. The experiments were carried out using a hypersonic shock tunnel, with Mach number of 10 and duration of 10 m.s.

Visualization of Shock Wave by Electric Discharge

Theme O PTICAL systems such as schlieren systems, MachZehnder interferometers, and shadowgraphs have been used as typical methods to observe shock waves around models. However, any shock shape cannot necessarily be observed by these optical systems. For instance, it is difficult to measure a cross-section of a shock wave around a model, especially that around a winged body as shown in Fig. 1. In this case the shock shape in the shaded region (dotted line) cannot be observed by any optical method, because a part of the optical axes is intercepted by the body. In this paper, an observing method of shock waves by using an electric discharge has been tried. The principle of the method is based on the fact that a radiation intensity of an electric discharge depends on gas densities. When an electric discharge is generated across a shock wave, the radiation intensity in the shock layer is different from that in the freestream according to the difference of each density, consequently the location of the shock wave can be easily found by taking a photograph of this discharge column. Since the location of the electrodes may be chosen arbitrarily and the discharge column can be observed from any direction, it will be expected to be able to observe cross-sectional shock shapes or the shock wave in a shaded region as stated above. W I N G E D BODY

New method for measurement of surface pressure using magnetic tape

A new method of surface pressure measurement has been developed using magnetic tape as a sensor—instead of the usual strain gage, piezogage or semiconductor —within a diaphragm-type pressure transducer. The method is based on the idea that a pressure value applied to the diaphragm is related to the deflection of the diaphragm, and the deflection can be related to the value of magnetization strength sensed in the tape. The merit of the new method is that it can be easily applied for measurement of pressure distributions on model surfaces because many pressure transducers are contained in a single sheet only about 1-mm thickness. The proposed method can be used in the high-temperature, short-duration measurement conditions, and so it is well suited to hypersonic wind-tunnel use. The sheet can be bonded onto a model surface. In this study, experiments using the new pressure sensor were performed in a hypersonic gun tunnel at a Mach number of 10 for a duration time of 10 ~2 s. Pressure distributions around two models in hypersonic flow were measured successfully.

Visualization of Shock Wave around Hypersonic Diamond Cone by the First Electric discharge Method

The shock shape around a slender diamond cone traveling at hypersonic speed was visualized by using the first electric discharge method. The visualized shock shape was compaired with the result obtained theoretically. Both the results agreed comparatively well. From this comparison, it was comformed that the first electric discharge method is useful for visualizing three dimensional shock shapes around hypersonic vehicles.

A Qualitative Theory on the First Electric Discharge Method for Visualizing Three-Dimensional Shock Shapes

A qualitative theory of the first electric discharge method for visualizing shock shapes was established by considering the relation among the radiation intensity from the electric discharge, excitation function vs. electron energies, and gas molecular number density. By establishing the theory, it was found there exists the most suitable experimental condition for visualizing shock shapes. A three dimensional shock shape around a delta wing with a body in a hypersonic flow has been visualized successfully by utilizing the knowledge.

A New Visualizing Method of Streamlines Around Hypersonic Vehicles by Using Electrical Discharge

This paper describes a new visualizing method of streamlines around models in hypersonic flows by using an electrical discharge. First, the visualization of a streamline around a wedge is carried out. The result shows that the visualized streamline in the shock layer is approximately parallel to the wedge surface. The theoretical streamline is considered to be parallel to the wedge surface. From this, it is proved that the new method is available for the visualization of streamlines around hypersonic vehicles. Moreover, the visualization of a streamline around a more complicated model shape is carried out, successfully.

A New Visualizing Method for Three-Dimensional Shock Shapes by Using Electrical Discharge

This paper describes a new method for visualizing three-dimensional shock shapes around hypersonic vehicles by using an electrical discharge. The method is based on the following ideas : When an electrical discharge is generated across a shock wave, the shock wave can be seen as a dark portion in the electrical discharge. The three-dimensional shock shape can be visualized by taking a discharge photograph in the rear direction of the flow. In this paper, the reasons the dark portion occurs are mentioned theoretically by considering the ionization efficiency and the excitation function versus electron energies in the electric fields generated between a pair of electrodes.

Inviscid hypersonic flow around a conical flat-top wing-body combination.

The steady hypersonic flow around a slender conical flat-top wing-body has been solved by applying the equivalence principle, which is the theory that the problem of steady hypersonic flow past a slender body is equivalent to the problem of unsteady flow in a plane. Then, the problem of this conical flat-top wing-body becomes into the problem of an expanding motion of a hemi-cylinder with a plane wing. The flowfield of this expanding body has successfully been solved by means of a conformal transformation and a superposition technique. Moreover, the other problems of small angles of attack, vortices, shock shape etc. have been also solved. As for the experimental investigation, the flow around the expanding body has been visualized. The experimental results agree well with the theoretical ones.