The aerodynamic coefficients are essential parameters to determine the flight performance of aircraft. They are estimated by wind tunnel tests and CFD analyses, and it is important to assess the validation by comparing those estimated from actual flight test data. In this comparison, uncertainties of estimated parameters are of strong interest, therefore the analysis of these uncertainties is a very important issue. In this paper, aerodynamic coefficients with their uncertainties are estimated from flight data, and their validation is implemented by the inverse simulation method. Then the causes of uncertainties are investigated and dominant causes are quantitatively identified. The aircraft weight has a dominant effect on C_L, while the angle of attack and the thrust have a large effect on C_D.

Transient characteristics of entire engine system affect control method of the engine system. A quasi-transient simulator called Hypersonic Engine Dynamic Simulator (HEDS) was developed for the purpose of analyzing the transient behavior of a scramjet engine system. The simulator was constructed using the volume junction method, which is a type of finite volume method, and was introduced with a parallel computing function using the MPI library. In this study, the transient characteristics at the starting sequence of a scramjet engine equipped with an expander cycle was analyzed. In the startup transient analysis, two factors (the time from high-speed airflow inflow to the main valve opening and the time from the main valve opening to ignition) that affect the system startup were focused. In addition, constraints on the system were set to evaluate results of the analysis. As a result, there existed cases in which the maximum rotational speed of the turbo pump was much higher than expected when the interval between the inflow of high-speed airflow and the opening of the main valve was increased. In addition, there was also a delay time between ignition and fuel temperature rise. Therefore, the time from the main valve opening to ignition should be as short as possible. In the control phase, it was necessary to manipulate those two factors appropriately in order to bring the system to a steady state in a short time. HEDS was found to be a very effective tool for understanding the behavior of the system at the operating point and constructing a control method.

To improve short takeoff and landing performance and stall characteristics of fixed-wing unmanned aerial vehicles, a Multi-Slotted Variable-Camber Morphing Wing was proposed. This airfoil is composed of five components connected, and the aerodynamic characteristics can be adjusted by changing the configuration of each airfoil. In this study, the arrangement of components of the morphing airfoil is optimized aerodynamically by defining 12 design variables, and the obtained Pareto solutions are analyzed to identify essential design variables and components to improve the aerodynamic performance of the entire airfoil. As a result, it was shown that the position of the fourth and fifth components is essential for the lift coefficient, the distance between components is essential for the drag coefficient. Moreover, the position of the second component is essential for the pitching moment coefficient.

Burgers' equation is a fundamental equation for describing several flow phenomena such as traffic, shock waves, turbulence. The optimal feedback control method, so-called model predictive control, has been proposed for Burgers' equation. However, the model predictive control method is inapplicable to systems whose all state variables are not exactly known. In the previous studies, a state estimation method based on the Unscented Kalman Filter has been proposed for the system described by Burgers' equation under the assumption that the flow velocities are known only in a limited part of the spatial domain. In this study, we propose a method combining the model predictive control and the state estimation method based on unscented Kalman filter for the system described by Burgers' equation. The effectiveness of the proposed method is verified by numerical simulation.

The body shape of a snake is generally not suitable for gliding flight. However, the flying snake Chrysopelea paradisi deforms its round body into a semi-cylindrical shape, and glides in the air without stalling in the same wriggling motion as when moving on the land or water surface. Moreover, the flying snake is not damaged when landing after gliding flight. In this investigation, we discuss the gliding flight and landing mechanism of the flying snake from aerodynamics perspective. We made a two-dimensional body model of the flying snake. Using this model, we carried out the wind tunnel experiments and two dimensional numerical simulations. When the flying snake body lies normal to the flow, the gliding ratio is about 2.4 and it lands safely. In particular, we found that the pitching moment can be reduced to zero by slightly moving the center of gravity.