Yasunori Nagata

平成24年度宇宙航行の力学シンポジウム（2012年12月13日-14日. 宇宙航空研究開発機構宇宙科学研究所）, 相模原市, 神奈川県資料番号: SA6000010033

43rd Fluid Dynamics Conference / Aerospace Numerical Simulation Symposium 2011 (July 7-8, 2011. Waseda University, International Conference Center), Tokyo JapanIn the electrodynamic flow control, a weakly-ionized plasma flow behind the strong shock wave is controlled by the applied magnetic field around are entry vehicle. According to the experimental measurement with an arc-jet wind tunnel, the electrodynamic effect is influenced by the magnetic configuration. In this study, the numerical MHD simulation was performed to investigate the influence of the inclination angle and the intensity of the magnetic field. The present results show that the circulation region is generated around a body when the magnetic field intensity exceeds a threshold value. The manner of the variation of the aerodynamic force associated with the magnetic field inclination strongly depends on the magnetic field intensity because the circulation region causes the drastic change of the flow field and electromagnetic field.Physical characteristics: Original contains color illustrations

43rd Fluid Dynamics Conference / Aerospace Numerical Simulation Symposium 2011 (July 7-8, 2011. Waseda University, International Conference Center), Tokyo JapanFor a high-enthalpy flow, it has been suggested that shock layer formed by the body in a weakly-ionized flow is enhanced as a result of the interaction between a magnetic field applied to the body and the flow. According to the theory, the scale effect of the interaction is organized by the interaction parameter defined by the ratio of the magnetic force to inertial force of the flow, which includes not only the intensity of the applied magnetic field but also the flow parameters such as density. In this study, the scale effect of the interaction is investigated experimentally, by varying not only the intensity of the applied magnetic field but also other parameters. For this purpose, the high-enthalpy flow generated in the expansion tube is employed. It was confirmed that the influence on the shock layer by the interaction is almost proportional to the interaction parameter as the theory suggests.Physical characteristics: Original contains color illustrations

43rd Fluid Dynamics Conference / Aerospace Numerical Simulation Symposium 2011 (July 7-8, 2011. Waseda University, International Conference Center), Tokyo JapanThe effect of the boundary layer development associated with the shock wave propagating through the low pressure tube part of the expansion tube was investigated. For this purpose, the low pressure tube flow was simulated by the time-dependent axisymmetric Navier-Stokes equation with ideal gas assumption and coefficient of viscocity of given by Sutherland's formula. It is found that because of the finite formulation process of the shockwave, the initial resultant shock speed exceeds the theoretical prediction but, afterwards, the shock speed keeps decreasing because of the boundary layer development initiated from the intersection of the shock wave and the tube wall. Simultaneously, the contact surface is accelerated. As a result, the region between the shock wave and the contact surface becomes narrow and the test flow arrival becomes faster than the theoretical estimations. The present simulation results agree with the experimental results at least qualitatively. However, numerical calculation models must be improved, such as real gas effects or three dimensional calculation.Physical characteristics: Original contains color illustrations

A flexible aeroshell for the atmospheric entry vehicle has attracted attention as an innovative space transportation system because the aerodynamic heating during atmospheric entry can be reduced dramatically due to its low ballistic coefficient. Our group has researched and developed a capsule-type vehicle with a flare-type membrane aeroshell supported by an inflatable torus frame. The characteristics of inflatable aeroshell are not well understood particularly under the environment where the ambient pressure varies significantly. Therefore, the flight experiment using a scientific balloon is conducted in order to acquire basic techniques and knowledge for constructing the system of a vehicle with the inflatable membrane aeroshell. The diameter, mass, and ballistic coefficient of the experimental vehicle are 1.264 m, 3.375 kg, and 2.69 kg/m^2, respectively and its aeroshell consists of a torus which can be inflated by gas pressure and a thin membrane flare made of nylon. The inflatable aeroshell was deployed and the experimental vehicle was separated from the balloon at an altitude of 25 km. After the separation, the vehicle flied 30 minutes without problems. All the sequences are properly executed, and following results were achieved. 1) Remote deployment system of the inflatable aeroshell by sending a command from a ground station was successfully conducted. 2) Data of aerodynamic characteristics, for example drag coefficient, were obtained after analyzing a flight data. 3) As for a structural strength of inflatable aeroshell, valuable data was obtained which can be compared with preliminary structural test using low-speed wind tunnel.

ADCS (Aero-Dynamic Computational System), which is a CFD (Computational Fluid Dynamics) solver to simulate flow using Multi-block technique, was developed. Parallel programming with MPI library was utilized to achieve high performance and obtain applicability for large-scale aerospace problems. The ADCS solves the time-dependent conservation law form for the Reynolds-Averaged Navier-Stokes (RANS) equations on structured grids. The finite difference method is used for spatial discretization. Several turbulence models are available. The reduction of memory usage was achieved by modified data structure with a new feature of Fortran 90 language. The parallelized code was verified and its performance was tested. It shows that the code is efficient to conduct large-scale computations by using MPI parallelization. Several test cases were conducted to validate the numerical accuracy and test performance for parallel computational system.

The expansion tube is known as a simple facility realizing a high enthalpy flow and has been employed in a variety of applications ranging from a super-orbital reentry capsule to an electrodynamic heat shield technique. In this study, the flow generated in the expansion tube was experimentally and theoretically investigated to evaluate the test time period and the test flow condition realized in the expansion tube about several flow conditions. The pitot pressure was measured at the test section and the secondary pitot pressure jump which indicates the contact surface arrival was observed. This fact is also confirmed through observations of the flow field around the pitot pressure probe. For the highest flow velocity case, the simple theoretical method assuming equilibrium flow gives a good estimation about flow conditions and test time. However, for the other cases, this estimation method must be improved.

An automatic grid tool for a supersonic transport configuration with leading- and trailing-edge flaps was developed. It employed the commercial software Gridgen to modify the shape and grid for different combination of flap deflection angles. With the automatic tool, time cost for shape modification and grid generation is dramatically reduced. In this paper, the automatic process of shape modification and grid generation are described, and examples of the generated grid and computational result are presented.

A multi-block CFD solver developed by JAXA was modified for parallel computation. Parallel programming MPI library was utilized to improve the performance and the applicability for large-scale problems. The parallelized code was verified and its performance was tested. It shows that the code is efficient to conduct large-scale computations by using MPI parallelization.

A magneto plasma sail (MPS) is a new propulsion system for a deep space mission such as the Voyager. A thrust of MPS is considered to be generated by utilizing the interaction between the solar wind and the magnetic field inflated by plasma injection from the spacecraft. In order to estimate the thrust, we performed magnetohydrodynamic (MHD) simulations including plasma injection. Our results indicate that the thrust of MPS increases with the beta value of the injected plasma. Additionally, from a viewpoint of the thrust performance, the thrust of a MPS is larger than the reaction force generated by the plasma injection under the condition where the beta value is less than 10-4.5.