丸 祐介

研究紹介 : 試験設備関連

研究紹介 : 共同研究報告

研究紹介 : 共同研究報告

研究紹介 : 機体関連

研究紹介 : 機体関連

This paper proposes a new aerodynamic device, which was designated multi-row-disk (MRD). This device has a cone and stabilizer disks being arranged in the axial direction. This device can arbitrarily change its aerodynamic characteristics by translating stabilizer disks. In the first part of this paper, the effect of several nose shape configurations including the MRD device on the aerodynamic characteristics is reported. By increasing the number of stabilizer disks, zero-lift drag and induced drag can be reduced. It was also found that putting cavities on the conical surface is effective for improving longitudinal static stability. In the second part, the effect of cavity flow instability on pressure and strain oscillation is reported. We drew the design criterion that the configuration of stabilizer disks should be determined not to couple the 1st mode with pressure oscillation frequency, which can be predicted with Rossiter's formula. (c) 2007 Elsevier Ltd. All rights reserved.

This paper reports an experimental study on flow oscillation characteristics of an aerodynamic control device that we have proposed. The device can achieve an enhancement of the aerodynamic control ability and a reduction of the flow instability by adding multiple stabilizer disks to a conventional aerospike so as to divide the flow separation region into multiple cavities. In this device, several axisymmetric cavities are formed. It is well known that pressure oscillation is induced around cavities. In this study, the characteristics of the pressure oscillation of several cavities on a cone surface were investigated experimentally by unsteady pressure measurements in a wind tunnel testing. The conical-cavity pressure oscillation had a feature that the oscillation level is large in case that a length-to-depth ratio of the cavity is large; the oscillation frequency can be predicted by the famous Rossiter formula, which is reported in many previous researches on a single rectangular cavity. It was also found that adding thin disks into the large cavity is effective in the reduction of the pressure oscillation level downstream of the cavities. In addition, disk structural vibration measurements were conducted simultaneously with the unsteady pressure measurements, revealing that a flutterlike vibration could occur when the pressure oscillation frequency agrees with the disk eigenfrequency.

This paper reports experimental studies on telescopic aerospikes with multiple disks. The telescopic aerospike is useful as an aerodynamic control device; however, changing its length causes a buzz phenomenon, which many researchers have reported. The occurrence of buzzing might be critical to the vehicle because it brings about severe pressure oscillations on the surface. Disks on the shaft produce stable recirculation regions by dividing the single separation flow into several conical cavity flows. The telescopic aerospikes with stabilizer disks are useful without any length constraints. Aerodynamic characteristics of the telescopic aerospikes were investigated through a series of wind tunnel tests. Transition of recirculation/reattachment flow modes of a plain spike causes a large change in the drag coefficient. Because of this hysteresis phenomenon and the buzzing, the plain spike is unsuitable for fine aerodynamic control devices. Adding stabilizer disks is effective for the improved control of aerospikes.

In this paper, a concept of a new variable-geometry aerodynamics device, which is designated “Multiple-Row-Disk (MRD) device,” is introduced. The MRD device divides large separation region around the shaft of an aerospike into several small cavity flows with multiple disks arranged on the shaft. Experimental studies on aerodynamic characteristics of conical nose with axisymmetric cavities were conducted in order to evaluate a feasibility and a fundamental characteristics of the MRD device. It was found that the MRD device could improve not only drag characteristics compared to the conventional aerospikes, but also static longitudinal stability characteristics compared to the conical nose.

In this paper, experimental studies on telescopic aerospikes with multiple disks are reported. The telescopic aerosoike is useful as an aerodynamic control device; however, changing its length causes a buzz phenomenon, which many researchers have reported. The occurrence of buzzing might be critical to, the vehicle because it brings about severe pressure-oscillations on the surface. Disks on the shaft produce stable recirculation regions by dividing the single separation flow into several conical cavity flows. Therefore, the telescopic aerospikes with stabilizer disks are useful without being any length constraints. Aerodynamic characteristics of the telescopic aerospikes were investigated using wind tunnel tests. Transition of recirculation/reattachment flow modes of a plain spike causes a large change in the drag coefficient. Because of this hysteresis phenomenon, the plain spike is unsuitable for fine aerodynamic control devices. Adding stabilizer disks is effective for the improved control of aerospikes.