• 대기
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• 제20권3호
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• pp.343-353
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• 2010

A regional wind network with complex surface conditions must be designed with sufficient space and time resolution to resolve the local circulations. In this study, the spatial variations of the wind field observed in the Seoul and Jeju regional networks were evaluated in terms of annual, seasons, and months to assess the spatial homogeneity of wind fields within the regional networks. The coherency of the wind field as a function of separation distance between stations indicated that significant coherency was sometimes not captured by the network, as inferred by low correlations between adjacent stations. A meso-velocity scale was defined in terms of the spatial variability of the wind within the network. This problem is predictably most significant with weak winds, dull prevailing wind, clear skies and significant topography. The relatively small correlations between stations imply that the wind at a given point cannot be estimated by interpolating winds from the nearest stations. For the Seoul and Jeju regional network, the meso-velocity scale has typically a same order of magnitude as the speed of the network averaged wind, revealing the large spatial variability of the Jeju network station imply topography and weather. Significant scatter in the relationship between spatial variability of the wind field and the wind speed is thought to be related to thermally-generated flows. The magnitude of the mesovelocity scale was significantly different along separation distance between stations, wind speed, intensity of prevailing wind, clear and cloudy conditions, topography. Resultant wind vectors indicate much different flow patterns along condition of contributing factors. As a result, the careful considerations on contributing factors such as prevailing wind in season, weather, and complex surface conditions with topography and land/sea contrast are required to assess the spatial variations of wind field on a regional network. The results in the spatial variation from the mesovelocity scale are useful to represent the characteristics of regional wind speed including lower surface conditions over the grid scale of large scale atmospheric model.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.77-78
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• 2015

Laminar burning velocities have been predicted by constant volume combustion chamber, counter flow burner and others. In this study, the measured flame propagation velocities in an assembled annular stepwise diverging tube were plotted with respect to equivalence ratio, length scale, and velocity scale. Three dimensional approach to understand the flame propagation velocity including laminar burning velocity is investigated, and the surface provides the correlation among quenching distance, propagation velocity, and equivalence ratio.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
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• pp.159-162
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• 2012

Combustion in a narrow space has been interested as a model of meso-scale combustors (or micro-combustors). Premixed flames have been used to overcome flame quenching in a narrow space and non-premixed flames have been used to improve flame stabilization. In this study, overall characteristics of premixed flame and non-premixed flame in narrow combustion spaces were reviewed. Various effects such as the flow velocity distribution, thermal interaction, enhanced mass diffusion were discussed and an eventual structure of the flame at the extinction limit was introduced.

• 한국해양공학회지
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• 제20권5호
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• pp.23-29
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• 2006

A quasi depth-varying mathematical model for wind-generated circulation in coastal areas, expressed in terms of the depth-averaged horizontal velocity components and free surface elevation was validated and used to understand the diurnal circulation process. The wind velocity is considered as a dominant factor for driving the current. In this paper, three-dimensional numerical experiments that included the land topography were used to investigate the mesoscale air flaw over the coastal regions. The surface temperature of the inland area was determined through a surface heat budget consideration with the inclusion of a layer of vegetation.A series of numerical experiments were then carried out to investigate the diurnal response of the air flaw and wind-generated circulation to various types of surface inhomogeneities.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2013년도 제46회 KOSCO SYMPOSIUM 초록집
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• pp.41-43
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• 2013

In order to simulate and visually observe combustion phenomena in cylindrical radial-flow porous inert media, a radial multi-channel burner, made of transparent quartz plates, was fabricated. Flame stabilization characteristics and its pulsating instability in the burner were experimentally investigated with respect to various mixture flow rates and equivalence ratio. As a result, five different flame behaviors, such as stable flame, pulsating instability, sudden extinction, blowout and unstable extinction, were observed. Mean radial position of circularly arranged multi-flame and its averaged burning velocity were measured and then compared to the freely propagating flame. The multi-flame pulsation frequency is about several tens of Hz and it is supposed to be generated by the heat diffusion enhancement to cold pre-mixture by the intensive gas-solid interaction.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.1925-1930
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• 2006

흐름의 연직분포를 가정하여 수면에서 바닥까지 적분하여 평균화한 방정식에 기초한 준2차원 흐름모형을 연안해역에서의 취송류해석을 위해 적용되었다. 바람장의 변동에 따른 취송류장의 변동이 크게 나타나므로 본 연구에서는 육상지형의 영향을 고려할 수 있는 3차원 중규모 지역기상장 모형을 통해 연안해역에서의 시간에 따른 바람장변동을 수치해석 하였다. 육상에서의 지표면 열수지 변화를 위해 식생모델을 적용하였다. 기상장과 취송류 해석을 위한 수치모형실험결과 바람장의 변동에 따른 연안역에서의 흐름특성을 효과적으로 예측하고 있음을 확인하였다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.2161-2166
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• 2009

It is important for 0-6 hour nowcasting to provide for a high-quality initial condition in a meso-scale atmospheric model by a data assimilation of several observation data. The polarimetric radar data is expected to be assimilated into the forecast model, because the radar has a possibility of measurements of the types, the shapes, and the size distributions of hydrometeors. In this paper, an impact on rainfall prediction of the data assimilation of hydrometeor types (i.e. raindrop, graupel, snowflake, etc.) is evaluated. The observed information of hydrometeor types is estimated using the fuzzy logic algorism. As an implementation, the cloud-resolving nonhydrostatic atmospheric model, CReSS, which has detail microphysical processes, is employed as a forecast model. The local ensemble transform Kalman filter, LETKF, is used as a data assimilation method, which uses an ensemble of short-term forecasts to estimate the flowdependent background error covariance required in data assimilation. A heavy rainfall event occurred in Okinawa in 2008 is chosen as an application. As a result, the rainfall prediction accuracy in the assimilation case of both hydrometeor types and the Doppler velocity and the radar echo is improved by a comparison of the no assimilation case. The effects on rainfall prediction of the assimilation of hydrometeor types appear in longer prediction lead time compared with the effects of the assimilation of radar echo only.

• 한국연소학회지
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• 제18권3호
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• pp.24-30
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• 2013

Flame stabilization characteristics of premixed flames in an annular coaxial 5-tubes burner (AC5TB) were investigated experimentally. The AC5TB was made of five quartz tubes, and the flame stabilization conditions in that burner were investigated with the variation of equivalence ratio and the flow velocities. Flame behaviors inside of narrow annular tubes could be observed directly. Overall flame stabilization conditions were similar to that of the previous study, while the flame behaviors and structures were different mainly due to the controlled uniform distribution of the velocities in channels. Flame flashback conditions were thought to be governed by the competition between heat release rate, heat loss and heat recirculation in each channel. Stationary flames at a fixed location were compared in its velocity distribution and burned gas temperature across the channel. This AC5TB can be a basic configuration for the development of flame stabilization model of porous media combustors, and it will help understand about the real behavior of flames in meso-scale combustion spaces.

• 한국지구과학회지
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• 제38권1호
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• pp.24-34
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• 2017

등학교에서 사용되는 고급지구과학 교과서에서는 서풍이 대규모 산맥을 넘어갈 때 풍하측에 파동이 발생하는 현상을 개략적인 그림으로 제시하여 간략히 이론적으로만 설명하고 있다. 이 현상은 편서풍 파동 현상으로 산을 넘어가는 공기 기둥의 소용돌이도(잠재와도) 보존 이론으로 설명될 수 있다. 그러나 우리나라와 같이 소규모 산맥이 존재하는 지역에서 관측자료를 바탕으로 중규모 편서풍 파동 현상에 대한 사례 연구는 부재하였다. 또한 서풍에 의한 파동이 형성되는 조건인 산맥의 폭과 길이에 따라 서풍의 풍속, 지속시간을 명확히 규정한 선행연구는 미미하다. 따라서 본 연구에서는 우선적으로 소백산맥을 대상으로 근처의 지표 관측소에서 관측한 지역별 상세관측자료를 이용하여 파동이 실제로 형성되는 지 확인하였다. 또한 소백산맥에 의하여 지표 근처에서 서풍 파동이 생성되기 위한 서풍의 최저속도인 임계 속도를 이론적으로 유도하여, 대략 $0.6m\;s^{-1}$의 값을 구하였다. 더 나아가 기상청 2014년 지역예보모델의 4-차원 자료동화 자료를 추가하여 소백산맥 풍하측 서풍 파동 발생의 연중 빈도와 서풍 파동의 진행 발달과정을 고도별로 분석하였다. 발생한 서풍 파동은 meso-${\beta}$ 또는 -${\gamma}$ 규모였다. 파동의 생성 및 소멸은 풍속 또는 풍향과 밀접한 관계가 있으며, 풍속이 감소함에 따라 산맥에 의한 서풍 파동은 점차 소멸되었다. 서풍이 강할수록 상층에 meso-${\beta}$ 규모의 파장을 갖는 와도 생성 비율이 높았다. 분석 범위를 동아시아 권역으로 넓혔을 때 중국 동북부 옌산 산맥에서도 서풍 파동 현상을 확인할 수 있었다. 본 연구의 결과는 유체지구에 대한 이론과 현상의 이해, 특히 우리나라 산맥에 의해 발생하는 대기의 파동 현상을 실제 관측 자료를 바탕으로 이해를 돕는 교육 자료로 활용될 수 있다.