This study focuses on the aerodynamic performance of the supersonic biplane at the low-speed region. The performance was evaluated and discussed through Computational Fluid Dynamics (CFD) and Experimental Fluid Dynamics (EFD). The result of the CFD simulation was compared with the experimental result to validate the simulation and confirmed to be reliable. Therefore, the CFD results were employed to derive the aerodynamic performance coupled with the theoretical equations. In the wind tunnel experiment, the three-component force measurement was conducted to obtain lift, drag and pitching moment coefficients. The wake survey was conducted to measure the drag in detail. The results proved the low-speed aerodynamic performance of the supersonic biplane can be described by the classical ``general biplane theory'' reasonably well.
Space robots will be needed in the future space missions. So far, many types of space robots have been developed, but in particular, Intra-Vehicular Activity (IVA) space robots that support human activities should be developed to reduce human-risks in space. In this paper, we study the motion learning method of an IVA space robot with the multi-link mechanism. The advantage point is that this space robot moves using reaction force of the multi-link mechanism and contact forces from the wall as space walking of an astronaut, not to use a propulsion. The control approach is determined based on a reinforcement learning with the actor-critic algorithm. We demonstrate to clear effectiveness of this approach using a 5-link space robot model by simulation. First, we simulate that a space robot learn the motion control including contact phase in two dimensional case. Next, we simulate that a space robot learn the motion control changing base attitude in three dimensional case.
This paper investigates wing aerodynamic characteristics used for bi-plane micro-air vehicles. Surface pressure distributions of two-dimensional biplane airfoils (4% cambered-plate airfoil) were measured at a chord Reynolds number of 6.4 × 104. Lift characteristics of three-dimensional biplane rectangular wings (aspect ratio of 3) were also measured at the same Reynolds number. It was indicated that the behaviors of laminar separation bubble formed both on the upper and lower airfoils/wings affects their lift characteristics. Bi-plane wings with positive stagger, i.e. protruded upper wing indicated higher maximum lift coefficient. This is caused by different behaviors of laminar separation bubble formed on the wing.
Temporal plasma-fluid behavior and performance of a pulsed MPD thruster are numerically examined for respective propellants of Ar and He under some current waveforms, each of which has a finite rise time and approaches asymptotically to a maximum current value. The current rise time and the mass flow rate are varied in the range of 1--20μs and 0.4--1.2g/s respectively. The maximum discharge current is set to the critical current. After an ignition, a shock wave is produced and propagates toward the downstream region. Under the condition of a constant discharge time, the specific impulse and the thrust efficiency are improved with shortening a current rise time mainly due to the increase in the impulse bit with regard to electromagnetic thrust. Using He propellant, the ratio of the magnetic thrust to the total thrust is increased from 50% (Ar) to 89% (He), which results in the higher specific impulse of He (≈2,500s) than that of Ar (≈800s).
It is well known that landing-gear noise is one of the dominant noise sources during the approach phase of a civil airplane. Therefore, it is important to understand the noise generation mechanism and reduce the noise from a landing gear. In this study, steady-state flow analysis around a landing gear model is reported using unstructured-mesh method. To predict the landing gear noise directly, unsteady flow analysis is necessary. However, even from the steady-state analysis, information related with the noise generation could be gained by focusing on the accelerated region or wake interference. From these preliminary results, basic flow field information is obtained to understand the flow physics around the complicated landing gear geometry.