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정서윤(Seo Yoon Jung),정용만(Yongmann M. Chung) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.9
Time delay effects on near-wall turbulent structures are investigated by performing a large-eddy simulation of a transient turbulent flow in a pipe. To elucidate the time delay effects on the near-wall turbulence, we selected the dimensionless acceleration parameter which was used in the previous study. Various turbulent statistics revealed the distinctive features of the delay. It was shown that the dynamic Smagorinsky model is valid to capture the alterations of the turbulence physics well. A dimensionless time for the responses of the flow quantities was introduced to give the detailed information on the delay of the nearwall turbulence. The conditionally-averaged flow fields associated with Reynolds shear stress producing events show that sweep and ejections are closely related to the delays of the turbulence production and the turbulence propagation toward the pipe center. The present study suggested that the enhanced anisotropy of the turbulence in the initial and transient stages would be a challenging problem to standard turbulence models.
레이놀즈 수의 시간 증가율에 따른 난류 채널 유동의 변화
정서윤(Seo Yoon Jung),김경연(Kyoungyoun Kim) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
Effects of the increase rate of Reynold number on near-wall turbulent structures are investigated by performing direct numerical simulations of transient turbulent flows in a channel. The simulations were started with the fully-developed turbulent channel flow at Re<SUB>τ</SUB>= 180, and then temporal accelerations were applied. During the acceleration, the Reynolds number, based on the channel width and the bulk mean velocity, increased almost linearly from 5600 to13600. To elucidate the effects of flow acceleration rates on the near-wall turbulence, we selected the wide range of the duration of acceleration. Various turbulent statistics and instantaneous flow fields revealed that the rapid increase of flow rate invokes the bypass-transition like phenomena in the transient flow. By contrast, the flow evolves progressively and the bypass transition does not occur clearly during the mild flow acceleration. The present study suggested that the transition to the new turbulence in transient channel flow is mainly due to the flow acceleration rate not because of the ratio of the final Reynolds number to the initial Reynolds number.
레이놀즈 수의 시간 증가율에 따른 난류 채널유동의 변화
정서윤(Seo Yoon Jung),김경연(Kyoungyoun Kim) 대한기계학회 2016 大韓機械學會論文集B Vol.40 No.7
레이놀즈 수의 시간 증가율이 벽면난류 구조에 미치는 영향을 난류 채널유동에 대한 직접수치모사를 수행하여 조사하였다. 완전 발달된 Reτ = 180의 난류 채널유동이 가속을 받게 되어 평균속도로 무차원화된 레이놀즈 수가 5600에서 13600까지 선형적으로 변화하게 된다. 다양한 가속 시간에 대한 계산을 수행하여 벽면난류에 대한 가속율의 효과를 파악하였다. 유량의 증가율이 큰 경우에는 우회 천이와 유사한 현상이 발견되었으며, 유량의 증가율이 낮은 경우에는 우회 천이 현상이 거의 나타나지 않았다. 본 연구 결과는 초기 레이놀즈 수와 최종 레이놀즈 수의 비 보다는 레이놀즈 수의 시간 증가율이 채널내 과도유동에서의 우회 천이 현상 발생에 주요인자 임을 제시한다. Effects of the increase rate of Reynold number on near-wall turbulent structures are investigated by performing direct numerical simulations of transient turbulent channel flows. The simulations were started with the fully-developed turbulent channel flow at Reτ = 180, then temporal accelerations were applied. During the acceleration, the Reynolds number, based on the channel width and the bulk mean velocity, increased almost linearly from 5600 to 13600. To elucidate the effects of flow acceleration rates on near-wall turbulence, a wide range of durations for acceleration were selected. Various turbulent statistics and instantaneous flow fields revealed that the rapid increase of flow rate invoked bypass-transition like phenomena in the transient flow. By contrast, the flow evolved progressively and the bypass transition did not clearly occur during mild flow acceleration. The present study suggests that the transition to the new turbulent regime in transient channel flow is mainly affected by the flow acceleration rate, not by the ratio of the final and initial Reynolds numbers.
손유진,정서윤,강기완,정민정,장인수,Sohn, Yu-jin,Jung, Seo-yoon,Kang, Ki-wan,Jeong, Min-jeong,Jang, In-soo 대한한방내과학회 2017 大韓韓方內科學會誌 Vol.38 No.4
Objectives: This study provides an evaluation of the effectiveness of acupuncture for the treatment of essential tremors (ETs) using randomized controlled trials (RCTs). Methods: Nine databases (PubMed, CINAHL, EMBASE, OASIS, NDSL, CNKI, Wanfang, J-STAGE, and CiNii) and the keywords "Essential tremor", "Benign tremor", "Familial tremor", and "Acupuncture" were used to compile RCTs that used acupuncture to treat ETs. Studies that were not RCTs, such as case studies, reviews, and essays, were excluded. The methodological quality of each RCT was assessed using the Cochrane risk-of-bias tool, and where appropriate, meta-analyses were performed. Results: Initially, 819 studies were found, but 773 were excluded after title and abstract screening. After further screening of the resulting 46 papers, eight RCTs were selected that had been published between 2003 and 2016, and the total effective rate (TER) was used as the primary evaluation method for all eight studies. It was found that the TER was significantly higher in treatment groups (83.33-96.7%) than in control groups (56.5-80.0%), and seven studies included in the meta-analysis showed positive results for acupuncture for ETs (Risk Ratio: 1.43, 95% Confidence Interval: 1.21-1.69, P<0.0001) Confidence Interval. Conclusions: This meta-analysis of clinical trials suggests that acupuncture is effective for treating ET patients; however, further studies are needed or larger populations to prove its effectiveness.
이진(Jin Lee),정서윤(Seo Yoon Jung),성형진(Hyung Jin Sung),Tamer A. Zaki 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
Direct numerical simulations (DNS) of turbulent boundary layer in a water flow over a heated wall were performed. By taking temperature-dependent viscosity of atmospheric water, the influence of viscosity stratification on the turbulent structure was scrutinized. In the heated flow, both turbulence intensities and the Reynolds shear stress were decreased significantly. The reduction of the Reynolds shear stress resulted from weakened turbulent vortical structures in the outer region. Conditionally averaged velocity fields around the ejection and the head of the hairpin vortex showed that spatial extent and population of the outer vortical structures were decreased for the heated flow.
김평화 ( Pyung-wha Kim ),정서윤 ( Seo-yoon Jung ),이은희 ( Eun-hee Lee ) 대한한방부인과학회 2018 大韓韓方婦人科學會誌 Vol.31 No.4
Objectives: This study was performed to analyze the prescriptions of Korean herbal medicine which had been commonly used during postpartum period. Methods: We searched literature on postpartum cares with Korean Herbal medicine in 4 domestic search engines. After that, we conducted eligibility screening based on inclusion and exclusion criteria. Results: 1. We selected total 48 studies. There were 40 clinical studies (25 case reports and 15 case series) and 8 animal experimental studies. 2. Of the 40 clinical studies, other treatments were used together with herbal medicine : acupuncture (28), chuna manipulation (3), and pharmacopuncture (5). 3. Of the 25 case reports, the most common symptoms were musculoskeletal symptoms (8), followed by mental disorders including postpartum depression (5). Various prescriptions of herbal medicine were used depending on the diseases or symptoms. 4. In 15 case series, 665 subjects in 11 case series had taken Saenghwa-tang-gagam within 1~2 weeks after childbirth, and the average duration of Saenghwa-tang-gagam administration were 9±4.97 days. 498 subjects in 9 studies were breast-feeding, and there were no side effects reported. 5. All experimental studies were about the recovery, the immunity and the breast-feeding associated puerperal characteristics. Also, 3 studies used Saenghwa-tang as an intervention. Conclusions: Saenghwa-tang can be commonly used for the purpose of prevention and care of the postpartum symptoms within the first 1~2 weeks after childbirth for 10 days. Also, various prescriptions of herbal medicine may be used depending on the diseases or symptoms, and can be conducted with other treatments like acupuncture, cupping, moxibustion, pharmacopuncture and chuna manipulation.