Naoyuki Okamura
(Tokyo University of Science, Japan)

Liquid hydrogen fueled hypersonic transport airplanes which can fly across the Pacific Ocean in 2 hours has been researched at JAXA. A multi-disciplinary optimization with aerodynamic, thermal structure, propulsion system and flight trajectory has been done. Design of shapes has been discussed on aerodynamic performance at Mach5. However, low-speed aerodynamic performance of the shapes has not been focused in the former research. In this paper, low-speed aerodynamic performance of a reference shape is studied numerically by FaSTAR, which is a CFD solver to simulate flow using unstructured grid by a cell centered finite volume method. Results of CFD analyses of the reference shape are compared with those of low-speed wind tunnel test. Moreover, some strakes in front of wings are added to the reference shape to improve the low-speed aerodynamic performance. Based on results, a guideline of improvement of low-speed aerodynamic shape is obtained.

Naoya Murakami
(Teikyo University, Japan)

The Space Shuttle is going to retire itself for the reason of the deterioration and the high maintenance cost. As a future space transportation system, a reusable space plane is expected. When a space plane is realized, it will fly at hyper- or supersonic speed over the land. Therefore, it is thought that the sonic boom becomes the big issue for a space plane. At first in this study, sonic boom intensity of the Space Shuttle is predicred from the wind tunnel test data conducted by NASA with Waveform Parameter Method. The result show that considering how to reduce sonic boom is also important for future space transportation system. Reduction of sonic boom intensity of a space plane with a hypersonic speed is attempted with Seebass-George-Darden-Sriram method. As a result, the optimized far-field pressure signatures for the space plane is estimated to be accepted by people of 65 percent on the basis of assessment with use of sonic boom simulator. For future works, demonstration of these results is necessary by CFD or wind tunnel testing.

Yuji Oshiro
(University of the Ryukyu, Japan)

In this paper, an unsteady supersonic jet using shock tube with small high pressure chamber with an elliptical cell is experimentally studied. In this experiment, the sudden discharged air jet is considered to be an ablated plume for the simplicity of the experiment. The working fluid is adapted as air. The experiments were performed with unsteady wall static pressure measurements of inside of the elliptical cell and with shlieren method for visualization of flow field through small windows. The position of the unsteady static pressure measurement was assumed to be theta=30, 45 and 60 from the center axis of the elliptical cell. The main parameter of the experiments is the pressure ratio of the high pressure chamber ph to the low pressure chamber pb, ph/pb=10.7~47.4. As a result, the unsteady wall pressure variations show that there are two peaks inside of the cell. According to the preliminary calculation, the first peak is expected to be caused by the traveling shock wave and the second one is considered to be the arrival of the plume to the pressure sensor. Moreover, the photographs of the incident traveling shock wave in the elliptical cell toward the exit hole of the cell were taken.

Akito Koda
(University of the Ryukyu, Japan)

In this study, an experiment was performed to clarify the flow field, in which the jets were normally inserted into a main supersonic flow surrounded by a porous cavity. Figure shows the concept of the schematic diagram of the mixing enhancement with porous cavity. The cavity is attached to the lower wall of the duct. The jet is normaly injected into the main flow, and a bow shock wave is generated slightly upstream of the jet. It causes a pressure difference between the upstream and the downstream of the bow shock wave resulting in the recirculation flow between the main flow and the cavity. As a result, it is found that the position of the starting shock wave is severely affected by the number and the alignments of the jets. The pressure distribution on the upper and lower wall showed that position of the starting shock wave is moved toward the downstream. Especially, the downward displacement the starting shock wave occurred notably in the case of the three jets aligned parallel to the main flow. The experimental results suggest that the jets behave as the variable second throat, causing swallowing of the starting shock wave.

Hitomi Iizuka
(Waseda University, Japan)

An optical method, namely high-speed photography analysis, for void fraction measurement of cryogenic two-phase flow is now under development. The pre-cooled turbojet engine, currently undevelopment by JAXA, uses liquid hydrogen as the fuel. To construct the engine start sequence, the flow characteristics such as heat transfer and pressure drop of the boiling hydrogen flowing must be investigated. The void fraction is a key parameter associated with these values. When the void fraction becomes high, bubbles may overlap one another in the image taken from one-direction, and therefore each one cannot be recognized separately. Hence, the stereo photographing method, shown in Figure 1, was instead adapted. Images seen from two directions are synchronously taken by one camera using 4 no-distortion mirrors and two LED lights. Two images seen from the horizontal and vertical directions are obtained at the same time. They are binarized such that liquid phase is colored white and gaseous phase black. The average luminance value is calculated by counting the white points on each image. The two average luminance values obtained by the horizontal and vertical directions are compared in a correlation model. The model, which is designed prior to the experiment, inversely predicts the void fraction.

Yuji Gima
(University of Ryukyus, Japan)

An experiment on the active control of a shock wave and main flow in a transonic diffuser were carried out. The bimorph type piezo ceramic actuator was set at a throat of the diffuser so that the cross section of the throat can be varied. Using this technique, the diffuser can be considered to be a variable cross sectional internal flow. The effect of the piezo actuator on the diffuser flow is evaluated mainly by wall static pressure measurements. The input control signal to piezo actuator was monitored downstream of the throat through a pressure sensor, which is processed with a digital signal processor. The digital signal processor changes the gain and the sign of its input signal. The root mean square of the wall static pressure is also calculated in order to check the shock position, in which the increase in the rms denotes the approaching shock wave toward the measuring position. As a result, the clear response from the piezo actuator to the shock wave behavior and the pressure fluctuation were confirmed, which suggests that the system has potentially promising applications to noise and vibration reductions of the jet engines and to high power speakers.