Bleed Slot을 사용한 응축충격파의 피동제어

백승철,권순범,김희동,Baek, Seung-Cheol,Kwon, Soon-Bum,Kim, Heuy-Dong 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.7

The current study describes experimental and computational works on the passive control of the steady and unsteady condensation shock waves, which are generated in a transonic nozzle. The bleed slots are installed on the contoured wall of the transonic nozzle in order 10 control the magnitude of the condensation shock wave and its oscillations. For computations, a droplet growth equation is copuled with two-dimensional Navier-Stokes equation systems. Computations are carried out using a third-order MUSCL type TVD finite-difference scheme with a second-order fractional time step. Baldwin-Lomax turbulence model is employed to close the governing equations. An experiment using an indrafi transonic wind tunnel is made to validate the computational results. The current computations represented well the experimental flows. From both the experimental and computational results it is found that the magnitude of the condensation shock wave in the bleed slotted nozzle is signi ficantly reduced, compared with no passive control of solid wall. The oscillations of the condensation shock wave are successfully suppressed by a bleed slot system.

초음속 노즐에서 발생하는 응축충격파 진동의 피동제어

백승철,권순범,김희동,Baek, Seung-Cheol,Kwon, Soon-Bum,Kim, Heuy-Dong 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.7

Rapid expansion of a moist air or a stream through a supersonic nozzle often leads to non-equilibrium condensation shock wave, causing a considerable energy loss in flow field. Depending on amount of latent heat released due to non-equilibrium condensation, the flow is highly unstable or a periodical oscillation accompanying the condensation shock wave in the nozzle. The unsteadiness of the condensation shock wave is always associated with several kinds of instabilities as well as noise and vibration of flow devices. In the current study, a passive control technique using a porous wall with a plenum cavity underneath is applied for the purpose of alleviation of the condensation shock oscillations in a transonic nozzle. A droplet growth equation is coupled with two-dimensional Navier-Stokes equation system. Computations are carried out using a third-order MUSCL type TVD finite-difference scheme with a second-order fractional time step. An experiment using an indraft wind tunnel is made to validate the present computational results. The results show that the oscillations of the condensation shock wave are completely suppressed by the current passive control method.

출판저널 칼럼

백승철,Baek, Seung-Cheol 대한출판문화협회 1989 출판저널 Vol.37 No.-

부족팽창 습공기 제트의 마하디스크 거동에 관한 수치적 연구

백승철(Seung-Cheol Baek),권순범(Soon-Bum Kwon),김희동(Heuy-Dong Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11

A computational study is performed to clarify the characteristics of supersonic moist air jet issuing from a simple sonic nozzle. The effects of the initial supersaturation on the Mach disk diameter and location. the barrel shock wave and jet bondary structures are investigated in details. The axisymmetric, compressible, Navier-Stokes equations, coupled with growth equation, are solved using a third-roder MUSCL type TVD finite-difference scheme. It os found that the Mach disk diameter increases with an increase in relative humidity of moist air. while its location is not significantly dependent on the relative humidity. As the relatibe hamidity increases, the barrel shock wave and jet boundary are more expandsd 엳 to the local static pressure rise of nonequilibrium condensation.

地籍學의 硏究動向과 當面課題에 關한 硏究 - 碩ㆍ博士學位 論文을 中心으로

백승철(Baek Seung Cheol),이범관(Lee Beom Gwan) 한국지적학회 2006 한국지적학회지 Vol.22 No.1

  본 연구의 목적은 국내에 발표된 지적학 관련 석ㆍ박사학위 논문의 동향을 조사ㆍ분석하고, 이를 토대로 지적학의 연구동향과 당면과제를 제시하는데 있다. 이를 위해 1972년부터 2004년 12월까지 연구된 학위논문 301편을 연구대상으로 하였다. 연구방법으로는 역사적 접근방법을 사용하였고, 문헌조사법과 인터넷조사법을 병행하였으며, 기술적(記述的)분석법을 사용하였다.<BR>  분석 결과, 지적학의 연구동향으로는 첫째, 우리나라 지적학 관련 최초의 학위논문은 1972년 이종환의 “한국 지적행정에 관한 연구”로 나타났다. 둘째, 지적학 연구는 기초이론분야보다는 응용분야에 치중한 것으로 나타났다. 셋째, 연구주제의 중복성과 유사성으로 인해 논문의 질이 낮게 평가되었다. 넷째, 1980년대는 지적행정분야, 1990년대는 지적기술분야, 2000년대는 기타분야의 연구가 상대적으로 증가한 시기였다. 다섯째, 대부분의 학위논문은 지적관련 대학원이 설치되지 않은 대학에서 더 많이 발표된 것으로 나타났다.<BR>  이상을 토대로 지적학의 발전을 위한 당면과제를 제시하면 첫째, 기초이론분야의 활성화방안이 모색되어야 하고 둘째, 지적관련 대학원의 활성화방안이 필요하며 셋째, 지적학의 대중화를 위한 대국민 홍보활동이 강화되어야 할 것이다. 넷째, 학위논문의 질적 향상을 위해 대학간 논문심사위원의 교류가 강화되어야 할 것이다.   The objective of this study was to present the research trends and the immediate problems on cadastre, based on the survey and the analysis in accordance with the trend of masters" and doctoral theses being submitted so far in Korea. For the purpose of achieving the study, the 301 theses were subjected to deal with these researches, which have been submitted between 1972 and December 2004.<BR>  In the process of the procedure, historical, philological approach and computerized investment have been used in concurrently descriptive analysis.<BR>  The consequences of analysis are as follows.<BR>  First, the thesis entitled “A Study on Korea’s Cadastral Administration” was submitted for the first time in Korea in 1972, by Lee Jong-hwan. Secondly, cadastral research has been focused on application of fields rather than basic theories. Thirdly, the quality of theses was evaluated to be inferior due to repetitive and similar theses. Fourthly, the central subjects of cadastral research have been in transition as to respective decades on the contrary, i.e., cadastral administration in the 1980s, cadastral technology in the 1990s and other scopes in the 2000s. Fifthly, the theses were a lot more submitted in the university in which the relevant graduate school is not established up until now.<BR>  Hereupon, some immediate problems were analyzed in order so that cadastral science can be developed in the near future.<BR>  Based on these data, urgent immediate affairs were presented as follows, in order that Cadastre can be developed sooner or later.<BR>  The bottom line is that all of us should consider those four categories on activation just like these, Secondly the relevant graduate school could be publicized to people nationwide, Fourthly, inter-university interchanges should be strengthened and associated with examiner committee in campus for improvement qualitatively.

비정상 팽창파에 의해 발생하는 비평형 응축현상에 관한 연구

백승철(Seung-Cheol Baek),권순범(Soon-Bum Kwon),김희동(Heuy-Dong Kim) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5

A numerical simulation of the unsteady flow in standard shock tube, where the nonequilibrium condensation occurs due to the upstream propagation of the unsteady expansion waves, is presented. The two dimensional unsteady Navier-Stokes equations fully coupled with droplet growth equation are solved by third-order MUSCL type TVD finite difference scheme, and compared with previous experimental results. It is found that the major characteristics of the nonequilibrium condensation of moist air in a shock tube are very different from those in supersonic wind tunnels. There is a significant discrepancy between the point of lowest local static pressure and the one which condensate mass fraction starts to increase. Therefore It is likely that the definition of the onset of nonequilibrium condensation is not the lowest local pressure point but the one condensate mass fraction starts to increase.

부족팽창된 습공기 초음속 제트에 관한 연구

백승철(Baek Seung-Cheol),김희동(Kim Heuy-Dong),권순범(Kwon Soon-Bum) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4

Supersonic free jets discharging from an orifice or a nozzle have long been research subject with a number<br/> of engineering applications and have mainly been investigated using dry air or other gas without any<br/> condensation effects. The major characteristics of those supersonic jets are now well known in terms of jet<br/> pressure ratio and ratio of specific heats of gas. Recently, the supersonic jets of superheated steam or moist air<br/> are being used in many industrial applications, in which case is expected that the condensation effects might<br/> alter the fundamental structure of the dry air jet. The present study aims to investigate the supersonic moist air<br/> jet and to clarify the condensation effects on the jet structure. An experiment is carried out using an indraft<br/> wind tunnel facility. The relative humidity of moist air is controlled at the nozzle supply, and the jet pressure<br/> ratio is varied to obtain the moderately under expanded flows at the exit of the nozzle. It is found that the<br/> relative humidity of moist air can change the diameter and location of Mach Disk.

Prandtl-Meyer 유동에서 발생하는 응축충격파의 피동제어

백승철(Seung-Cheol Baek),권순범(Soon-Bum Kwon),김희동(Heuy-Dong Kim) 한국항공우주학회 2004 韓國航空宇宙學會誌 Vol.32 No.1

Prandtl-Meyer 유동에서 발생하는 웅축충격파를 제어하기 위한 피동제어법의 유효성을 조사하기 위해 계산과 실험을 수행하였다. 본 연구에서 사용된 제어법은 균질 응축을 수반하는 다공벽과 공동을 사용한 피동제어법이다. 실험결과와 비교하기 위해 액적성장방정식과 완전히 결합된 2차원 압축성 Navier-Stokes 방정식은 3차 오더 MUSCL 타입 TVD 유한차분법을 사용하여 풀었다. 본 연구의 피동제어법은 응축충격파의 강도감소에 유효하며, 또 응축충격파의 비정상 운동이 다공벽/공동 시스템을 이용한 제어법으로 완전히 억제되었다. Both computational and experimental works are performed to clarify the effectiveness of a passive control method applied to the condensation in Prandtl-Meyer flow. The present study makes use of the passive control strategy employing a porous wall and cavity system with homogeneous condensation. Two-dimensional compressible Navier-Stokes equations, fully coupled with a droplet growth equation, are solved to reproduce the experimental results using a third-order MUSCL type TVD finite-difference scheme. It was found that the strength of condensation shock wave in Prandtl-Meyer flow were weakened. Furthermore, the unsteady motion of condensation shock wave was effectively suppressed using the passive cavity/porous system.

초음속 습공기 제트에서 발생하는 마하디스크의 거동

백승철(Baek Seung-Cheol),김희동(Kim Heuy-Dong),권순범(Kwon Soon-Bum) 한국추진공학회 2003 한국추진공학회 학술대회논문집 Vol.2003 No.5

건설VE에 대하여

백승철(Seung Cheol Baek) 대한토목학회 2020 대한토목학회지 Vol.68 No.2