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Experimental investigation of a supercritical airfoil boundary layer in pitching motion
Mehran Masdari,Mohsen Jahanmiri,Mohammad Reza Soltani,Arshia Tabrizian,Mohammad Gorji 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.1
In this study, the boundary layer velocity profile on the upper surface of a supercritical airfoil in a forced sinusoidal pitching motion was measured and experimentally investigated. Measurements were performed using a boundary layer rake, including total pressure tubes positioned at 25 % of the chord far from the leading edge on the upper surface. For static measurements, the effects of the angle ofattack between −3° and 14° and free-stream velocity between 40m sand 70m swere investigated; for dynamic measurements, theeffects of oscillation amplitude variation between ±3° and ±10°, reduced frequency from 0.007 to 0.0313, and mean angle of attack between −3° and 6° were studied during one oscillation cycle. Results indicated that the boundary layer thickness decreased in upstroke motion. Increasing the oscillation frequency led to the extension of hysteresis loops. Fast Fourier transform was used on pressure signals to study the amplitude of the dominant frequency in the velocity profile. Spectral analysis showed that the dominant forced frequency of oscillation in the boundary layer and the amplitude of this frequency were varied by increasing the reduced frequency and other parameters.
A Novel Fuzzy CMeans-Based Clustering Scheme for Wireless Sensor Networks
Smira Barzegari,Mohammad Masdari 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.2
WSNs consist of many low-cost autonomous sensors that are equipped with a small battery, data processing capabilities, and short-range wireless communication interfaces. They are often deployed for monitoring and surveillance of certain phenomena of interest. In this paper, we propose a fuzzy Cmeans-based clustering scheme which improves the network lifetime by creating symmetric clusters. It improves the random process of selecting the clusterhead nodes and by creating symmetric clusters reduces the total distances of intra-cluster communications. Thus, because, sensed data are transmitted to the closer clusterheads, our proposed clustering solution can prolong the network lifetime.