In this study, the nonequilibrium phenomena of the electronic excitation process behind hypersonic shock waves have been investigated through numerical analysis. In the analysis, the three-temperature model is employed and temperature profiles are computed along the distance from the shock front. In the three-temperature model, the translational–rotational, vibrational and electron-electronic excitation temperatures are separately described and the relaxation processes for each energy mode are considered. Numerical calculations are conducted under the conditions corresponding to the shock tube experiments conducted in our previous study and the results are compared with the experimental data. It is found that the calculated and measured vibrational temperature profiles are in good agreement. In contrast, the calculated electronic excitation temperature is much lower than the measured one, revealing the discrepancy in the modeling of the electronic excitation temperature. To investigate the effect of electron behavior, parametric studies are conducted using the three-temperature model. The calculated temperatures agree well with the measured temperatures by considering the electrons in the region ahead of the shock wave. This result suggests that the effect of electron behavior is significant for hypersonic shock waves and a detailed model to describe the nonequilibrium phenomena is needed.
Using the Abaqus® Computer-Aided Engineering (CAE) and Finite Element Analysis (FEA) software package, this study aims to numerically simulate the effect of the aerodynamic lift load experienced by a light all-metal aircraft in flight. The objective is to find how much stress and deflection is accumulated under the design ultimate load and also to identify the critical components in the wing structure. The load profile is idealized as a uniformly distributed load over the wing. The wing components such as spars, ribs, skin and struts are initially composed using SolidWorks® and then imported using Abaqus® CAE for stress and stiffness analysis. Various scenarios of load and geometry are analyzed and their results discussed. These scenarios include the choice of solid or shell elements of the components as well as the location of load concentration (pressure on the skin or direct load on the spar cap). Results show that for aircraft wing analysis purposes, the skin should be included in the analysis and the load should be applied on both the bottom and top surfaces. The meshing type is also found to have a greater effect on stress results than on deflection results.
A new method that combines an unscented information filtering (UIF) algorithm with an interacting multiple model (IMM) framework under a distributed multiple-sensor fusion architecture is proposed. The objective of the proposed scheme is to track a maneuverable target whose dynamics can be modeled with multiple nonlinear models, and whose measurements are obtained from and processed at distributed systems. An IMM is not suited for information fusion architectures because it does not use combined estimates and covariance from a previous step to predict values at the next time step, which is essential for information filtering. The proposed algorithm fuses data, such as the information state contribution and information matrix, of each UIF that is included in an IMM filter. Moreover, the proposed algorithm improves the tracking performance when the mode likelihood functions in the IMM, which are important in flight mode detection and change, are shared among the distributed systems. The tracking results from simulations indicate that the present filtering method can be a good solution to tracking of a maneuvering target in multiple-sensor environments.
Three-dimensional flow simulations through a turbine cascade are carried out for an exit isentropic Mach number of 0.79. The objective of the present study is to qualitatively and quantitatively clarify the effect of using an elliptic trailing edge (TE) instead of a circular one on the flow. Calculations are carried out using a parallel, turbulent, structured, single-block code and the delayed detached eddy simulation is employed for turbulence. We maintain the TE thickness (minor axis) and modify the other axis (major axis). Time-averaged pressure and heat transfer coefficient distributions along the blade are presented with more attention paid to the TE region. The results show that increasing the major-to-minor axis ratio decreases both the heat transfer coefficient and loss. Therefore, designers can adjust this ratio according to application needs.
In the standing swimming of dolphins, which is often seen in aquariums, the total weight of the body is supported by the caudal fin in the water. It is clear that the thrust generated by the fanning motion of the caudal fin is equal to the body weight. In the study reported in this paper, a numerical simulation of the flow around the caudal fin (of the bottlenose dolphin) using the three-dimensional Navier–Stokes (3D NS) code for the standing swimming condition is conducted and the necessary power is computed. The power thus determined is approximately three to four times larger than the power necessary for the cruising swimming condition, determined by the performances observed to date for trained dolphins in aquariums. With this necessary power, we estimate the maximum speed the dolphin can attain, using the 3D modified doublet lattice method coupled with an optimum design method and the 3D NS code, obtaining a value of approximately 13 m/s, which is considerably higher than values observed in aquariums.
The aim of this paper is to design a robust automatic flight control system for a small-scale UAV helicopter. A nonlinear search based on differential evolution (DE) algorithm is conducted for a six degrees-of-freedom linear state-space model that matches the frequency-response data set. The accuracy of the identified model is verified by comparing the model-predicted responses with the responses collected during flight experiments. Based on the identified model, the H∞ loop shaping method is used to design the inner-loop of the unmanned helicopter in order to satisfy the flight performance requirements specified in the military standard ADS-33E. The greatest common right divisor method is used to solve the difficulties in choosing a proper weighting matrix in the H∞ loop-shaping procedure, compared with the traditional method, the system using the new method have a larger robust stability margin, the decoupling and the bandwidth of the system are also greatly improved. The simulation results prove high standard of the control performance of the unmanned helicopter system in accordance with ADS-33E.
The three telescopes on Hinode, a highly sophisticated solar observational satellite, must be able to simultaneously observe the same point on the sun in order to ascertain data on the physical mechanisms for activity and heating in the solar atmosphere. To fulfill this mission requirement, the telescopes must remain co-aligned to within 2.0 arcsec under the temperature fluctuations the satellite experiences while orbiting the earth. Hinode consists of two modules and a connecting structure. Most of the structural elements are made of CFRP in order to suppress thermal deformations. In particular, the laminate configuration of the CFRP in the module holding the telescopes was carefully designed in terms of not only its stiffness and strength but also its coefficient of thermal expansion and thermal conductivity. A thermal deformation analysis was performed to estimate the co-alignment drift on-orbit and a thermal deformation test was conducted to verify the estimation. The results showed that the structural design would sufficiently suppress the drift on-orbit. Measurements on-orbit were conducted using the image of the sun, and the measured drift was in good agreement with the estimation.