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Investigation and Improvement of Pusher-Propeller Installation Effect for Flying Wing UAV
Wenbo Shi,Jie Li,Shuai Zhao,Zhao Yang 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.2
This paper presents a collaborative experimental and numerical research to investigate the influences of the installation of propeller on aircraft aerodynamic performance, and two approaches to mitigate the propeller installation effect are also analyzed. The configuration under investigation is based on a real flying wing unmanned aerial vehicle with a two-bladed pusher-propeller mounted on the aft part of its associated airframe. Reynolds-averaged Navier Stokes simulations coupled with a structured finite-volume cell-vertex based solver are applied to propeller uninstalled and installed configurations, and the numerical results are shown to be in good agreement with the experimental data. The comparative results obtained through prop-uninstalled and prop-installed cases show that the installation of the pusher-propeller leads to the decline of the maximum lift-drag ratio due to aerodynamic interactions between the propeller and airframe. Detailed analysis of the numerical results highlighted that the low pressure areas on the aft part of the airframe generated by the installation of the pusher-propeller will result in an increase of the base drag and hence a decline of the maximum lift-drag ratio. The feasibilities of center shaft extension and the modification of airframe geometry to mitigate the propeller installation effect are verified by numerical simulations, and results showed that proper propeller–airframe spacing and good designs of airframe geometry can effectively improve the flow characteristic and reduce the drag induced by propeller installation effect.
원보스(Wenbo Shi),장인주(InJoo Jang),유형선(Hyeong Seon Yoo) 한국전자거래학회 2007 한국전자거래학회지 Vol.12 No.4
Collins[1]등이 제안한 멀티 에이전트 테스트 베드는 발행/가입 시스템, 타임 릴리즈 암호법, 그리고 익명 통신 기법에 기반을 두고 있다. 최근 Jaiswal[2]등은 Collins의 멀티 에이전트 테스트 베드를 향상시키는 프로토콜을 제안하였다. 그러나 Jaiswal의 프로토콜 또한 데이터 재전송 공격, DOS 공격, 익명성 폭로 등과 사용자와 공급자 사이의 충돌 등의 문제에 대하여 취약함을 보인다. 본 논문에서는 DOS 공격의 가능성을 줄이고, 공급자에게 티켓 토큰과 처리 순번 제공함으로써 데이터 재전송 공격을 피할 수 있는 프로토콜을 제안한다. 또한 본 논문의 제안 프로토콜에서, 마켓은 공급자에게 난수 생성 방법과 결정과정의 데이터를 공유하기 위한 보간 다항식을 제공하여 사용자와 특정한 공급자 사이의 충돌을 피할 수 있게 한다. Recently, Jaiswal et al. proposed a protocol to improve the multi-agent negotiation test-bed which was proposed by Collins et al. Using publish/subscribe system, time-release cryptography and anonymous communication, their protocol gives an improvement on the old one. However, it is shown that the protocol also has some security weaknesses: such as replay data attack and DOS (denial-of-service) attack, anonymity disclosure, collusion between customers and a certain supplier. So proposed protocol reduces DOS attack and avoids replay data attack by providing ticket token and deal sequence number to the supplier. And it is proved that the way that market generates random number to the supplier is better than the supplier do by himself in guaranteeing anonymity. Market publishes interpolating polynomial for sharing the determination process data. It avoids collusion between customer and a certain supplie.
원보스(Wenbo Shi),장인주(InJoo Jang),유형선(Hyeong Seon Yoo) 한국전자거래학회 2007 한국전자거래학회지 Vol.12 No.4
본 논문에서는 사용자, 서비스 제공자, 그리고 키 분배센터인 KDC 사이의 인증 프로토콜과 키 분배기법에 관해 연구하였다. 본 논문에서 제안한 프로토콜은 대칭키 암호시스템과 시도-응답기법, Diffie-Hellman 기법, 해시 함수 등을 기반으로 하고 있으며, 사용자와 서버는 토큰 업데이트 과정에서 세션키를 업데이트한다. 업데이트된 세션키의 사용은 사용자에게 보다 보안성이 높은 인증과정을 수행 할 수 있도록 한다. 만일 KDC의 자료가 공격자에게 노출되었다 하더라도, 공격자가 세션키를 계산해 낼 수 없도록 설계되어 보안을 유지하게 된다. 본 논문에서는 제안된 프로토콜의 효율성과 진보된 보안성은 다른 프로토콜과의 비교와 분석을 통하여 우수함을 증명하였다. This paper proposes a key distribution and authentication protocol between user, service provider and key distribution center (KDC). This protocol is based on symmetric cryptosystem, challenge-response, Diffie-Hellman component and hash function. In the proposed protocol, user and server update the session key under token-update operation, and user can process repeated efficient authentications by using updated session keys. And another merit is that KDC needs not to totally control the session key between user and server in proposed protocol. Even an attacker steals the parameters from the KDC, the attacker still can not calculate session key. According to the comparison and analysis with other protocols, our proposed protocol provides good efficiency and forward secure session key.
Wenbo Huai,Yaoyao Shi,Hong Tang,Xiaojun Lin 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.2
High-speed rotating abrasive cloth wheel is a highly flexible material that can be used to polish aviation engine blades. In this study, sensitivity and relative sensitivity to processing parameters were described on the basis of an empirical model of surface roughness to control the polishing of rough surfaces with abrasive cloth wheels. A mathematical model of the sensitivity and relative sensitivity of surface roughness to processing parameters was also established on the basis of an orthogonal test of polishing TC4 blade workpieces by utilizing abrasive cloth wheels. The sensitivity of the analytical method for processing parameter interval was examined, and the division principle and approach for the stable and unstable ranges of processing parameters were proposed. The influence curve of polishing parameters on surface roughness was obtained by combining the analyzed ranges in the orthogonal test. The optimization of processing parameter interval was also presented to identify the optimal intervals of surface-roughness-oriented polishing parameters of abrasive cloth wheels. The polishing test based on an aviation engine blade confirmed that the optimal intervals of the parameters were reliable. This research provides a basis for theoretical studies and tests to evaluate blade polishing technique with abrasive cloth wheels and surface roughness control.
Aero-optical effects in the hypersonic flow field
Shi, Ketian,Miao, Wenbo,Li, Pengfei,Chen, Xiaoli The Society for Aerospace System Engineering 2015 International Journal of Aerospace System Engineer Vol.2 No.1
Aero-optical effects induced by the flow around the optical window degrade the performance of the IR seeker, especially for the hypersonic flow. For the thermochemical non-equilibrium flow, index of refraction model and optical transmission calculation method are developed to predict the aero-optical effects. The optical distortion is discussed for the typical optical widow shape and flow condition. The influence on aero-optical effects is analyzed.
Wenbo Huai,Yaoyao Shi,Hong Tang,Xiaojun Lin 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.7
As for blisk blade profile polishing, the “five-axis numerical control + flexible grinding head + elastic grinding tool” polishing process equipment has advantages of high precision, little interference, good adaptivity, etc.; in order that the elastic grinding tool (abrasive cloth wheel) can effectively fit in with the blade profile in the polishing process and polishing quality and efficiency can be improved, a polishing path programming method of the elastic grinding tool was studied, feed mode of the elastic grinding tool and parametric method of the blade profile were proposed, and calculation methods of offset surface, polishing spacing, polishing step size and cutter-axis vector were given; this polishing path programming method makes it possible for the flexible spindle mechanism keeps a reasonable pose during the polishing process so that the elastic grinding tool can not only effectively fit in with the blade profile but also the polishing force direction of the elastic grinding tool is basically identical with normal vector direction of the polishing point; the polishing test results indicate that: After polishing, blade surface roughness is smaller than 0.4 µm and blade profile tolerance is within the tolerance zone, thus satisfying technical requirements and indicating that the technology proposed in this paper can satisfy blisk blade profile polishing requirements.