A numerical analysis with sensitivity analysis on diurnal cycle of NOx and O3 was investigated to specify prime reactions with high impact on O3 deplations by emissions of exhaust gases. NOx concentration was measured in a vaccum chamber with emission of low-pressure mercury lamp, and numerical analysis of reactions in the chamber was conducted. Fifth-order BDF method was employed to calculate ordinary differential equations of concentrations and sensitivities. Reactions with high sensitivity for O3 concentration were limited, and chemical kinetics used in this calculation express history of NOx concentrations correctly in the chamber. This chemical kinetics was applied to the calculations of diurnal cycle of O3 concentration in stratosphere. As a result of this study, prime reactions with high sensitivities on O3 concentration is specified and history of concentrations of NOx, HOx and Ox was derived. Characteristics of NOx, HOx and Ox chemistry in the stratosphere was specified.
We have studied about the method for estimating control surfaces deflections δe, δa and δr from flight data. We called the newly developed algorithm as the “Modified Output Error Method.” Until now, we have succeeded in estimating lift coefficient CL, drag coefficient CD and three aerodynamic moment coefficients Cl,t, Cm,t, Cn,t, however, the estimation of control surface deflections were not implemented. In this paper, we introduced the “Yanagihara model” into our method, and by employing statistical procedures, we could estimate three control surface deflections δe, δa, δr fairly good.
The aerodynamic characteristics of water rockets are analyzed experimentally by wind tunnel testing. Aerodynamic devices such as vortex generators and dimples are tested and their effectiveness to the flight performance of water rocket is discussed. Attaching vortex generators suppresses the unsteady body fluttering. Dimpling the nose reduces the drag coefficient in high angles of attack. Robust design approach is applied to water rocket design for flight stability and optimum water rocket configuration is determined. Semi-sphere nose is found to be effective for flight stability and it is desirable for the safety of landing point. Stiffed fin attachment is required for fins to work properly as aerodynamic device and it enhances the flight stability of water rockets.
Flow visualization study was conducted to investigate the quasi-periodical behavior of the laminar separation bubble formed on a NACA0012 airfoil at the angles of attack α=11–12º. The Reynolds number based on the airfoil chord was Re=1.3×105. At α=11.5º, the flow over the airfoil quasi-periodically switches between a large separated flow and an attached flow with small separation near the leading edge at a frequency of about 2Hz. This attached flow resembles the flow pattern with a short bubble formed near the leading edge such as at α=10º. Ejection of large vortices downstream was observed during the quasi-periodical switching. The flow stays attached to the airfoil surface at α=11º. As the angle of attack is increased, the large separated flow becomes dominant. At α=12º, the flow is completely separated largely.
To predict the short bubble burst which is the cause of an airfoil leading-edge stall, it is necessary to establish an analytical method that can estimate the velocity distributions inside the short bubble when the airfoil angle of attack is increased. Viscous-inviscid interaction analysis has been conducted here to estimate the velocity distributions inside the short bubble. The eN method is applied to predict the point of transition onset inside the bubble. The eddy viscosity turbulence model is used whose constant is set to a uniform value inside the turbulent part of the bubble. The PIV measurements have been made for the short bubbles formed on NACA0012 airfoil at the chord Reynolds number of 1.3×105 at the angles of attack α of 6º, 8º and 10º to determine the values of constants used in the transition and turbulence models. Short bubbles formed on the same airfoil at the same flow conditions but at α=4º, 7º and 9º are analyzed by the present method. The results indicate that the present method predicts the formations of short bubbles fairly well at the angles of attack whose velocity profiles inside the bubble were not measured.
In the future, LEO spacecraft will be larger and higher powered. Because of the balance of currents through ambient space plasma, their main conductive body will have a higher negative potential without plasma contactor operation. When spacecraft operate with a higher voltage, more intensive arcing is suspected to occur on their surface. In this study, ground-based experiment was carried out to understand the arcing phenomenon and to examine influences of ambient space plasma on the arcing process. Simulating plasmas were generated by electron cyclotron resonance discharge. When arcing occurred on anodized aluminum sample (AAS) plates negatively biased by a capacitor in the plasma environment, the time variations in arc current and bias voltage were measured. Arc spot diameter was also measured. The experimental results showed that both the peak arc current and the total charge emitted by arcing increased with initial charging voltage and neutral particle number density. The diameter of arc spots increased with initial charging voltage although it was almost constant regardless of neutral particle density. Accordingly, high voltage operation of LEO spacecraft might bring drastic degradation of AAS by arcing depending on ambient plasma conditions.
The variable matrices method is proposed for self-identification of adaptive structures with variable physical parameters. The method applies the relation between the variation of vibration characteristics of the structures and variable physical parameters instead of their input-output relation. Numerical examples for self-identification with one-dimensional models indicate that the self-identification by variable stiffness and requested mode eigenvectors is realized within 1% errors. Also, the condition number of coefficient matrices of linear equations is introduced to examine the identification errors. Moreover, the numerical results show that the identification errors depend on the combination between the number of modes and the location of the variable stiffness devices. Finally, the results point out the significance of the changing range of the variable stiffness to realize accurate identification.