Shinji Nagai

Uncertainty Identification of Supersonic Wind-Tunnel Testing

In this study, a methodology for the identification of uncertainty of supersonic wind tunnel testing is developed. Instead of conventional multi-tunnel testing, multi-position testing is performed across the characteristic net of supersonic flow. From the variations in aerodynamic coefficients in body axes, the uncertainty caused by flow quality is identified about models of interest. Then, after the consideration of practically independent parameters, uncertainties of aerodynamic coefficients in stability axes are combined. Their validities are confirmed by correlation results of tunnel-to-tunnel comparison tests.

Dynamic Stability Analysis of a Reentry Lifting Capsule with Detached Eddy Simulation

The dynamic instability at transonic speeds is one of the big problems for development of re-entry vehicles. We need an accurate CFD tool that can predict the dynamic stability. To validate the CFD, damping coefficients are computed in a force oscillation manner and then compared with those by free rotation experiments. The three turbulence models are used: URANS with SA model, SA-DES, and SA-IDDES. Numerical simulations are carried out at M=0.4 and 1.1 where large limit cycle oscillations (LCO) were observed in the wind tunnel test. For the both Mach numbers, the results of the SA-DES and the SA-IDDES show better agreement with those by the experiments than those of the URANS. The characteristics of LCO are simulated well by CFD.

Flow Visualization by a Simplified BOS Technique

This paper proposes a simplified background oriented schlieren (S-BOS) technique for flow visualization. Our new method does not require a cross-correlation algorithm, which results in a more straightforward and automated technique. The difficulty in optimizing parameters and removing incorrect vectors, which is typical in the conventional BOS technique, is eliminated. It allows us to output images easily in real time. In the proposed BOS method, the image displacement associated with density gradient is algebraically calculated from the image intensities using a periodic background pattern. Because the proposed optical setup is simpler than the conventional schlieren technique, it could be used in various situations including field tests. A wind tunnel test was conducted using the proposed and conventional methods in a 1 m × 1 m supersonic wind tunnel and the images displayed the value of the new, simplified technique. Nomenclature A = resolution [mm] c = circle of confusion [mm] d = image dimension [mm] f = focal length [mm] f# = aperture value G = sensor size of 1 pixel [m] I = intensity K = Gladstone-Dale constant M = Mach number m = magnification factor n = refractive index P0 = tunnel stagnation pressure [Pa] X = displacement in the image along the x-direction [pixel] Y = displacement in the image along the y-direction [pixel] Zbo = distance between background and object [mm] Zoc = distance between object and camera lens [mm] Zbc = distance between background and camera lens [mm] Zs = depth of view [mm]  = angle of view [rad]  = deflection angle [rad]  = wavelength of light [m] i = incident angle [rad] r = refractive angle [rad]

The Effect of Diffuser Geometry on the Starting Pressure Ratio of a Supersonic Wind Tunnel

To reduce the starting and stopping loads at intermittent blow-down supersonic wind tunnels, diffuser performance is important to keep the starting pressure ratio as low as possible. A parametric study on diffuser performance for the JAXA 1m x 1m supersonic wind tunnel (JSWT) was conducted by numerical simulation. It was found that it is difficult to estimate performance by using only quasi-1D non-viscous theory because of shock waveboundary layer interactions. To improve the diffuser performance, a modified diffuser configuration was designed with a viewpoint of shock train phenomena. The modified JSWT diffuser is more slender than the original and its higher performance was confirmed by numerical simulation. This design concept was also validated experimentally with a 10% scale model tunnel at a Mach number of 3.0.

Key components development progress of high-power LPP-EUV light source with unique debris mitigation system using a magnetic field

Gigaphoton Inc. has been developing a CO2-Sn-LPP (LPP: Laser Produced Plasma) extreme ultraviolet (EUV) light source system for high-volume manufacturing (HVM) semiconductor lithography. Original technologies and key components of this source include a high-power carbon dioxide (CO2) laser with 15 ns pulse duration, a short wavelength solid-state pre-pulse laser with 10 ps pulse duration, a highly stabilized small droplet (DL) target, a precise DL-laser shooting control system and unique debris mitigation technology with a magnetic field. In this paper, an update of the development progress of the total system and of the key components is presented.

Aerodynamic Oscillation and Attitude Control Analysis for Reentry Capsule using OREX Flight Data and Wind Tunnel Data

Stable attitude control is essential for accurate reentry capsule guidance, and aerodynamic instability of a transonic region has been recognized as a key issue. To address this issue, we have been studying stable attitude control for lifting reentry capsule during reentry flights. As the first step of the study, we evaluated the aerodynamic stability and controllability of the Japanese ballistic reentry capsule named OREX (Orbital Re-entry EXperiment). The study compares reentry flight results with simulation results base on aerodynamic coefficients obtained from wind tunnel tests and aerodynamic damping coefficients modeled from wind tunnel tests and existing aerodynamic data-bases. We have also been analyzing the aerodynamic stability and controllability of a lifting reentry capsule by conducting attitude control simulations using aerodynamic damping coefficients estimated from the wind tunnel tests for dynamic stability characteristics. This paper describes the OREX system configuration, aerodynamic damping coefficients, reentry flight results, and a comparison of results obtained from flight data and simulations. Moreover we present the lifting reentry capsule model, aerodynamic damping coefficients estimated from wind tunnel tests, and comparison of results from wind tunnel test data and simulations.