Problems and accuracy of a wind tunnel test on a model helicopter are discussed from educational points of view. The rotor blade flapping motions and its aerodynamic characteristics were measured in forward flight, and their results are compared with well established data. The measurements confirm the coupling between longitudinal and lateral flap angles, and the effects of lock number and thrust levels on blade flapping motions. It is ascertained that the radio controlled model helicopter with suitable modifications is an effective instruction apparatus useful for understanding the basic aerodynamic and dynamic properties of a helicopter rotor.
For the sonic boom prediction and its minimization, it is very important to investigate the pressure signatures in the near field. In this paper, the near flow fields of a supersonic airplane are numerically simulated by solving the Euler equations using a space marching scheme. A solution-adaptive-grid method is incorporated in the computational procedure, where the grid in each marching plane is rearranged by monitoring the computed flow fields. The results show that this scheme gives the good prediction of the pressure signatures in the near field, and that the solution-adaptive-grid method improves the sharpness of the computed shock waves and the accuracy of the pressure signatures in the near field.
A self-balancing type axial-thrust balancing system referred to as “balance piston” was applied to the LE-7 LOX turbopump, the discharge pressure of which exceeds 30MPa. A research model turbopump showed that pressure distribution in the balancing chamber deviated greatly from the predicted distribution and that the axial clearance of the balancing-chamber inlet orifice became too small to maintain safety. Consequently, we attempted to determine the cause of these phenomena and to find methods of ensuring sufficient axial clearance of the inlet orifice. Two methods were attempted. In the first method, balancing holes directly connecting the balancing chamber and the main impeller inlet were made. In the second method, grooves were made on the casing wall facing the main impeller front shroud.
A combination of wave-polarization directions between transmitting and receiving antennas is discussed with a paricular interest in an improvement of the isolation on the basis of measurement of the diffractive wave, and the result is compared with theoretical values. The levels of the diffractive wave differes each other depending on a combination of the polarization direction, and the maximum amount of 15dB obtained as a difference between the maximum and the minimum levels of receiving shows that this method is significantly effective to undergo the improvement. It is also confirmed that the theoretical level of the wave calculated from an approximate equation agrees with the measurement. An extensive discussion of the improvement on the more practical condition remains as our future study.