• Title/Summary/Keyword: Propellers

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Unsteady Analysis of 3-Dimensional Hydrofoils Using a B-Spline Based High Order Panel Method

  • Jang, Hyun-Gil;Ahn, Byoung-Kwon;Lee, Chang-Sup
    • Journal of Ship and Ocean Technology
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    • v.12 no.2
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    • pp.16-31
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    • 2008
  • The lifting-surface programs have been used successfully in practice for the design and global performance prediction of the marine propellers. To predict the pressures on the blade for the strength analysis, the constant panel method has been a good alternative. To meet the need for more accurate information on the pressure near the tip region and the trailing edge of the blade, the higher order panel method (HiPan, hereinafter) based on a B-spline is developed and now available. However, there is an increasing demand to get the highly reliable unsteady behavior of the pressure near the tip region by the HiPan. The ultimate goal of our efforts is to develop the fully unsteady higher order panel code for the propeller. In the present paper, we will show the numerical procedure applicable to unsteady problems of the three dimensional hydrofoil in a sinusoidal gust and heave motions.

Control of Seesaw balancing using decision boundary based on classification method

  • Uurtsaikh, Luvsansambuu;Tengis, Tserendondog;Batmunkh, Amar
    • International Journal of Internet, Broadcasting and Communication
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    • v.11 no.2
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    • pp.11-18
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    • 2019
  • One of the key objectives of control systems is to maintain a system in a specific stable state. To achieve this goal, a variety of control techniques can be used and it is often uses a feedback control method. As known this kind of control methods requires mathematical model of the system. This article presents seesaw unstable system with two propellers which are controlled without use of a mathematical model instead. The goal was to control it using training data. For system control we use a logistic regression technique which is one of machine learning method. We tested our controller on the real model created in our laboratory and the experimental results show that instability of the seesaw system can be fixed at a given angle using the decision boundary estimated from the classification method. The results show that this control method for structural equilibrium can be used with relatively more accuracy of the decision boundary.

An investigation on the effect of the wall treatments in RANS simulations of model and full-scale marine propeller flows

  • Choi, Jung-Kyu;Kim, Hyoung-Tae
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.12 no.1
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    • pp.967-987
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    • 2020
  • A numerical analysis is carried out for the marine propellers in open water conditions to investigate the effect of the wall treatments in model and full scale. The standard wall function to apply the low of the wall and the two layer zonal model to calculate the whole boundary layer for a transition phenomenon are used with one turbulence model. To determine an appropriate distance of the first grid point from the wall when using the wall function, a formula based on Reynolds number is suggested, which can estimate the maximum y+ satisfying the logarithmic law. In the model scale, it is confirmed that a transition calculation is required for a model scale propeller with low Reynolds number that the transient region appears widely. While in the full scale, the wall function calculation is recommended for efficient calculations due to the turbulence dominant flow for large Reynolds number.

Development of Underwater ROV for Crack Inspection of River Facilities (하천 시설물 균열 검사를 위한 수중 ROV 개발)

  • Seong, Ho-Hwan;Lee, Jang-Myung
    • IEMEK Journal of Embedded Systems and Applications
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    • v.16 no.4
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    • pp.129-136
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    • 2021
  • River facilities and port structures require a regular inspection and diagnosis due to obsolescence. Currently, most river facilities are undergoing indirect inspection and diagnosis by divers. The underwater inspections are not feasible due to safety issues of divers and restrictions on working hours and environment. To overcome these issues, it is intended to conduct inspections of river facilities using underwater drones. In this research, an underwater ROV (Remote Operated Vehicle) has been developed, which is a kind of drone with propellers. As a key device of this research, an injection device has been attached to the underwater drone to conduct an operation test, a stable operation test of an underwater drone, and a test of attached sensors. The river facility inspection can be carried out optimally using the hovering control of the drone and injection systems. With the developed ROV system, hovering test and injection test have been performed to verify the feasibility of this development.

Prediction of Broadband Noise for Non-cavitation Hydrofoils using Wall-Pressure Spectrum Models (벽면변동압력을 이용한 비공동 수중익의 광대역소음 예측 연구)

  • Choi, Woen-Sug;Jeong, Seung-Jin;Hong, Suk-Yoon;Song, Jee-Hun;Kwon, Hyun-Wung;Kim, Min-Jae
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.25 no.6
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    • pp.765-771
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    • 2019
  • With the increase in the speed of ships and the size of ocean structures, the importance of flow noise has become increasingly critical in meeting regulatory standards. However, unlike active investigations in aeroacoustics fields for airplanes and trains, which are based on acoustic analogy methods for tonal and broadband frequency noise, only the discrete blade passing frequency noise from propellers is considered in marine fields. In this study, prediction methods for broadband noise in marine propellers and underwater appendages are investigated using FW-H Formulation1B, which can consider the mechanism of primary noise generation of trailing edge noise. The original FW-H Formulation 1B is based on the pressure correlation function tolackitsgeneralityandaccuracy. To overcome these limitations, wall-pressure spectrum models are adopted to improve the generality in fluid mediums. The comparison of the experimental results obtained in air reveals that the proposed model exhibits a higher accuracy within 5 dB. Furthermore, the prediction procedures for broadband noise for hydrofoils are established, and the estimation of broadband noise is conducted based on the results of the computational fluid dynamics.

Development of Panel-Based Rapid Aerodynamic Analysis Method Considering Propeller Effect (프로펠러 효과를 반영 가능한 패널 기반 신속 공력 해석 기법 개발)

  • Tai, Myungsik;Lee, Yebin;Oh, Sejong;Shin, Jeongwoo;Lim, Joosup;Park, Donghun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.49 no.2
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    • pp.107-120
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    • 2021
  • Electric-powered distributed propulsion aircraft possess a complex wake flow and mutual interference with the airframe, due to the use of many propellers. Accordingly, in the early design stage, rapid aerodynamic and load analysis considering the effect of propellers for various configurations and flight conditions are required. In this study, an efficient panel-based aerodynamic analysis method that can take into account the propeller effects is developed and validated. The induced velocity field in the region of propeller wake is calculated based on Actuator Disk Theory (ADT) and is considered as the boundary condition at the vehicle's surface in the three-dimensional steady source-doublet panel method. Analyses are carried out by selecting an isolated propeller of the Korea Aerospace Research Institute (KARI)'s Quad Tilt Propeller (QTP) aircraft and the propeller-wing configuration of the former experimental study as benchmark problems. Through comparisons with the results of computational fluid dynamics (CFD) based on actuator methods, the wake velocity of propeller and the changes in the aerodynamic load distribution of the wing due to the propeller operation are validated. The method is applied to the analysis of the Optional Piloted Personal Aerial Vehicle (OPPAV) and QTP, and the practicality and validity of the method are confirmed through comparison and analysis of the computational time and results with CFD.

Computational Simulation of Coaxial eVTOL Aircraft in Ground Effect (동축 반전 전기동력 수직이착륙기의 지면 효과에 대한 전산해석)

  • Yang, Jin-Yong;Lee, Hyeok-Jin;Myong, Rho-Shin;Lee, Hakjin
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.50 no.9
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    • pp.599-608
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    • 2022
  • Urban air mobility (UAM) equipped with rotor system is subject to ground effect at vertiport during takeoff and landing. The aerodynamic performance of the aircraft in ground effect should be analyzed for the safe operation. In this study, The ground effects on the aerodynamic performance and wake structure of the quadcopter electric vertical takeoff and landing (eVTOL) configuration equipped with coaxial counter-rotating propellers were investigated by using the lattice Boltzmann method (LBM). The influence of the ground effect was observed differently in the upper and lower propellers of the coaxial counter-rotating propeller system. There was no significant change in the aerodynamic performance of the upper propeller even if the propeller height above the ground was changed, whereas the averaged thrust and torque of the lower propeller increased significantly as propeller height decreased. In addition, the amplitude of the thrust fluctuation tended to increase as the propeller height decreased. The propeller wake was not sufficiently propagated downstream and was diffused along the ground due to the outwash flow developed by the ground effect. The impingement of the rotor wakes on the ground and a fountain vortex structure were observed.

Analysis of Characteristics of the Cancelled Districts of Housing Redevelopment Project - Focusing on Decision Tree Analysis - (재정비사업 해제구역 의사결정 특성 연구 - 의사결정나무기법 중심으로 -)

  • Lee, Do-Ghil
    • Journal of the Korean Regional Science Association
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    • v.37 no.4
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    • pp.49-59
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    • 2021
  • This study aims to identify the characteristics of the cancelled districts of housing redevelopment and housing reconstruction project. The subject of this study is 189 project districts(121 promoted districts, 68 cancelled districts). Both 121 promoted districts and 68 cancelled districts were analyzed by Decision Tree Analysis. The first separation of the release zone influencing factors was made by the Development Actors. In other words, the most important independent variable for determining the release zone influence factor was shown to be the presence or absence of propulsion actors. Of the 89 districts without propellers, 41 were lifted and 48 were promoted, and 9 out of 100 districts with propellers were lifted and 91 were promoted. The second separation of the impact factors on the zone was then made by Land Owners, and the probability of cancellation increased if the number of landowners was less than 468 and 37 out of 62 were removed. On the other hand, four out of 27 districts with more than 468 landowners were lifted and 23 districts were promoted. The third separation was made by the Average Land Assessment, and 35 zones were lifted below the standard of KRW 269.64 million/m2 approximately KRW 8.91 million per pyeong, and two zones were lifted at higher official prices. In the second division, the number of landowners was 468 or more, and in node4, four areas were removed from areas with a public land area ratio of 29.43% or more, and no areas less were released. This study used SPSS Statistics 26 S/W for analysis.

Preliminary study on the application of active noise control for reducing underwater radiated noise from naval vessel propellers (함정 프로펠러 수중 방사 소음 저감을 위한 능동 소음 제어 적용에 관한 기초 연구)

  • Dongwook Kim;Hanshin Seol
    • The Journal of the Acoustical Society of Korea
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    • v.43 no.6
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    • pp.615-623
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    • 2024
  • This study is a preliminary study about applying Active Noise Control (ANC) to reduce underwater radiated noise from ship propellers. In this research, simulations of active noise control using a virtual controller were performed to predict the noise reduction effects and changes in the sound field due to ANC on underwater propeller noise. The simulation results showed that while the Blade Passing Frequency (BPF) component of underwater propeller noise has a low frequency, the noise generated by the propeller has an impact waveform, necessitating a controller with a high sampling rate of over 40 kHz in the Filtered-X Lesat Mean Square (FxLMS) algorithm. Additionally, it was observed that in the case of Single-Input Single-Output (SISO) active noise control, noise reduction is achieved in the direction of the error microphone, but noise increases in the direction opposite to the error microphone. The findings of this study provide guidelines on the conditions and performance of noise reduction for active noise control of underwater propeller noise. Based on these results, the preliminary conditions and validation steps for active noise control of propeller noise in naval vessels are proposed.

A Study on Parts Manufacturer Approval in Civil Aviation Law (항공기 부품제작자증명에 관한 연구)

  • Lee, Kang-Yi;Jin, Young-Kwon;Lee, Jong-Hee;Lee, Kwang-Hee
    • The Korean Journal of Air & Space Law and Policy
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    • v.17
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    • pp.133-152
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    • 2003
  • Certification by Civil Aviation Law is necessary for aircraft parts and appliances as well as aircraft, engines, and propellers to ensure safety and reliability in operation. Advanced countries in aerospace industry as like U.S.A require Parts Manufacturer Approval for aircraft parts and Technical Standard Order Authorization for designated appliances. However, there are no legal requirements for certification of aircraft parts and appliances in Korea until now. This study presents the draft to revise Civil Aviation Law, which is applicable to set up domestic certification system and maintain it equivalent to U.S. Federal Aviation Regulation.

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