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RISS 인기검색어
- 검색키워드
- 저자 : 하콩투(Cong Tu Ha) (검색결과 8 건)
- 무료
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이선엽(Sun Youb Lee),하콩투(Cong-Tu Ha),이재화(Jae Hwa Lee) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
In a cooling system for thermal management of miniaturized and high-integrated electronic devices, the bubble with a phase change transports under the influence of the wall. However, although it is important to consider the influence of the wall due to the difference in flow patterns caused by the influence of the wall, most previous studies have not been studied the effect of the wall on a condensing bubble. In the present study, we perform numerical simulations for tube diameters (D<SUB>tube</SUB>) of 1.2≤D<SUB>tube</SUB>/D<SUB>0</SUB>≤3.0 based on the initial bubble diameter (D<SUB>0</SUB>) to investigate the effect of tube diameter on single bubble condensation in the subcooled flow. It is shown that as Dtube decreases, the condensation rate decreases due to the influence of the wall and the bubble moves to a higher position. Moreover, it has been found that at a small D<SUB>tube</SUB>, the reduction of heat and mass transfer is caused by the recirculation flow that occurs in the narrow gap between the bubble side and the tube wall.
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김동현(Dong-Hyun Kim),하콩투(Cong-Tu Ha),박원규(Warn-Gyu Park),정철민(Chul-Min Jung) 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6
Supercavitating torpedo uses the supercavitation technology that can reduce dramatically the skin friction drag. The present work focuses on the numerical analysis of the non-condensable cavitating flow around the supercavitating torpedo. The governing equations are the Navier-Stokes equations based on the homogeneous mixture model. The cavitation model uses a new cavitation model which was developed by Merkle(2006). The multiphase flow solver uses an implicit preconditioning scheme in curvilinear coordinates. The ventilated cavitation is implemented by non-condensable gas injection on backward of cavitator cone and the base of the torpedo. The comparison between the without and with ventilated cavitation numerical results, with ventilated cavitation using non-condensable gas injection is more efficient method. Also, this injection is attributed to be the instability of cavity.
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반구형 실린더 주위의 자연공동 및 환기공동 전산유동해석
김호윤(Ho-yoon Kim),하콩투(Cong-Tu Ha),박원규(Warn-Gyu Park),정철민(Chul-Min Jung) 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6
Cavitating flow is widely shown in many engineering systems, such as marine propellers, pump impellers, nozzles, injectors, torpedoes, etc. The present work focuses on the numerical analysis of the cavitating flow around the underwater vehicle. The governing equations are the Navier-Stokes equation based on homogeneous mixture model. The multiphase flow solver uses an implicit preconditioning scheme in curvilinear coordinates. The cavitation model uses a new cavitation model which was developed by Merkle(2006). Computations are carried out for two cavitating flows : natural cavitation and ventilated cavitation. The effect of ventilated cavitation is implemented by non-condensble gas injection on backward and forward of the body.
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Clark-Y 수중익형 주변 캐비테이션 유동장에 대한 수치적 고찰
구가람(Garam Ku),정철웅(Cheolung Cheong),하콩투(Cong Tu Ha),박원규(Warn-Gyu Park) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
Cavitation can be produced by localized pressure drop around a device which runs at a high speed in the water and generate stronger noise than non-cavitation flow. In this study, as a prior task to predict flow noise due to cavitation, basic numerical methods are developed to simulate cavitation flow and are applied to predict cavitation flow around a Clark-Y hydrofoil for the validation purpose. The prediction results are compared with the experiment and the simulation result obtained from the references available in terms of surface pressure distribution and the variation of periodic cavitation pattern. There are good agreements beween these results.
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Clark-Y 수중익형 캐비테이션 유동 소음 특성 분석
구가람(Garam Ku),김상현(Sanghyoen Kim),정철웅(Cheolung Cheong),하콩투(Cong Tu Ha),박원규(Warn-Gyu Park) 한국소음진동공학회 2016 한국소음진동공학회 학술대회논문집 Vol.2016 No.4
In this study, computational fluid dynamics techniques are applied to simulate cavitation flow and the noise caused by cavitation is predicted by applying the acoustic analogy to the predicted flow. The predicted results of cavitation flows are compared with the measurement and other prediction obtained from references available in terms of surface pressure distribution and the variation of periodic cavitation pattern. There are good agreements between these results. The noise sources are modeled as monopole and dipole sources. Then, the predicted noise results are analyzed in terms of directivity and SPL spectrum. Since the lift of the hydrofoil is higher than the drag, dipole source is dominant in the direction normal to the mean flow while monopole source is dominant in the direction parallel to the mean flow.
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Clark-Y 수중익형 주변 공동 현상에 의한 유동장과 소음 예측에 대한 수치적 연구
구가람(Garam Ku),정철웅(Cheolung Cheong),김상현(Sanghyeon Kim),하콩투(Cong-Tu Ha),박원규(Warn-Gyu Park) 대한기계학회 2017 大韓機械學會論文集A Vol.41 No.2
프로펠러와 같은 수중운동체 주변에서 발생하는 공동 현상은 물체를 부식시키고 소음을 발생시키므로, 공학적 측면에서 중요한 문제로 다루어지고 있다. 따라서 본 연구에서는 Clark-Y 수중익형에서 발생하는 공동 현상과 이로 인한 유동 소음을 예측하였다. 공동 예측 결과를 정량적으로는 수중익형 표면의 압력 분포, 정성적으로는 수중익형 주변 공동의 체적분율 변화 양상을 이용하여 비교하였으며, 실험결과 및 선행 연구와 비슷한 경향을 가짐을 확인하였다. 이러한 공동에 의한 유동 소음을 예측하기 위하여 음향상사법을 이용하였으며, 시간에 따른 체적분율 변화를 단극자 소음원으로, 수중 익형 표면에서의 비정상 압력섭동을 이극자 소음원으로 모델링하였다. 소음 예측 결과는 SPL과 방향성을 통해 분석하였고, 계산된 전체 주파수 영역에서 비정상 압력섭동에 의한 소음원이 지배적임을 확인하였다. Because the cavitation flow driven by an underwater propeller corrodes the materials around it and generates a high level of noise, it has become an important topic in engineering research. In this study, computational fluid dynamics techniques are applied to simulate cavitation flow, and the noise in the flow is predicted by applying the acoustic analogy to the predicted flow. The predicted results are compared with measurement results and other predictions in terms of surface pressure distribution and the temporal variation in liquid volume fraction. The predicted results are found to be in good agreement with the measured results. The source of the noise attributed to the time rate of change in the liquid volume fraction around the hydrofoil is modeled as a monopole source, and the source of the noise due to unsteady pressure perturbations on the hydrofoil surface is modeled as a dipole source. Then the predicted noise results are analyzed in terms of directivity and SPL spectrum. The noise caused by unsteady pressure perturbations was dominant in the entire frequency range considered in the study.
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비응축 가스에 의한 환기 공동이 포함된 수중 운동체 다상 유동장 해석
김동현(Dong-Hyun Kim),김호윤(Ho-Yoon Kim),하콩투(Cong-Tu Ha),박원규(Warn-Gyu Park),정철민(Chul-Min Jung) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.11
Supercaviatation torpedo uses the supercaviation technique that can reduce dramatically the skin friction drag. The present work fouses on the numerical analysis of the multiphase flow around the cavitator and tail of supercavitating torpedo. The governing equations are the Navier-Stokes equations for a homogeneous mixgture of liquid, vapor and non-condensable gas. The cavitation model uses a new cavitation model which is developed by Merkel. The multiphase flow solver uses an implicit preconditioning scheme in curvilinear coordinate. The effect of ventilated cavitation is implemented by using non-condensable gas injection on backward of cavitator and the base of the torpedo. This paper also considers the effect of different cavitator shapes. This work will be used for to develop a suitable cavitator shape for spuercavitating torpedo.
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