• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.195-200
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• 2010

Numerical investigation was conducted to study the effects of after-body configurations and nozzle lip on the PIFS(Plume Induced Flow Separation) and eat flux to the base face. Two dimensional and axi-symmetric non-equilibrium Navier-Stoke's solver with $k-{\omega}$ SST turbulence model was used to solve the launching vehicle type configuration with propulsive jet. The experimental result of Robert J. McGhee was compared with our computational results for code validation. Three types of the after-body configurations (Straight, Boat-tail, Flare type) were simulated for this study. And the nozzle lip effect was studies using the three types of base configurations same simulation conditions. As a result of numerical investigations, higher pressure ratio condition and boat-tail after-body configuration caused severe PIFS phenomenon but the flare type after-body configuration and low pressure ratio suppressed PIFS. Flare type after-body configuration and low pressure ratio case reduced heat flux to base face. The nozzle lip dispersed the heat flux widely along the base face and the nozzle lip.

• Wind and Structures
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• 제11권4호
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• pp.257-273
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• 2008

A number of passive aerodynamic drag reduction methods were applied separately and then in different combinations on an intercity bus model, through wind tunnel studies on a 1:20 scale model of a Mercedes Benz Tourismo 15 RHD intercity bus. Computational fluid dynamics (CFD) modelling was also conducted in parallel to assist with flow visualisation. The commercial CFD package $CFX^{TM}$ was used. It has been found that dramatic reductions in coefficient of drag ($C_D$) of up to 70% can be achieved on the model using tapered and rounded top and side leading edges, and a truncated rear boat-tail. The curved front section allows the airflow to adhere to the bus surfaces for the full length of the vehicle, while the boat-tails reduce the size of the low pressure region at the base of the bus and more importantly, additional pressure recovery occurs and the base pressures rise, reducing drag. It is found that the CFD results show remarkable agreement with experimental results, both in the magnitude of the force coefficients as well as in their trends. An analysis shows that such a reduction in aerodynamic drag could lead to a significant 28% reduction in fuel consumption for a typical bus on intercity or interstate operation. This could translate to a massive dollar savings as well as significant emissions reductions across a fleet. On road tests are recommended.

• 한국식품영양과학회지
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• 제11권1호
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• pp.31-36
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• 1982

Alcohol 농도별(濃度別)로 추출(抽出)된 원료삼(原料蔘)(수삼(水蔘),건삼(乾蔘), 미삼(尾蔘)) 엑기스에 대하여 이화학적(理化學的) 특성(特性), 당질(糖質) 및 총질소(總窒素) 함량(含量)을 분석비교(分析比較)한 결과(結果)를 요약(要約)하면 다음과 같다. 1. 인삼(人蔘)엑기스는 약간의 점성(粘性)을 가진 끈끈한 차갈색(茶褐色)으로 투광도(透光度)는 인삼(水蔘)이 35.9%, 건삼(乾蔘)이 29.2%, 미삼(尾蔘)이 28.9%이며, 이들은 산성(酸性)(pH 4.8-6.2)을 띄는 액상(液相)이었다. 2. 총당(總糖), 자당(蔗糖), 전분(澱粉)은 알콜농도(濃度)가 증가(增加)함에 따라 감소(減少)하는 경향(傾向)이었으며, 원료삼별(原料蔘別)로는 총당함량(總糖含量)이 건삼(乾蔘), 미삼(尾蔘), 수삼(水蔘)의 순(順)이고, 자당함량(蔗糖含量)은 수삼(水蔘), 건삼(乾蔘), 미삼(尾蔘)의 순(順)이며, starch함량(含量)은 미삼(尾蔘), 건삼(乾蔘), 수삼(水蔘)의 순(順)으로 많았다. 3. 원원당(遠元糖) 함량(含量)은 수삼(水蔘) 4.9-7.8%, 건삼(乾蔘) 8.6-12.8%, 미삼(尾蔘) 7.6-9.1%의 분포이고, 알콜농도가 증가(增加)함에 따라 수삼(水蔘), 미삼(尾蔘)은 감소(減少)하나 건삼(乾蔘)에서는 증가(增加)하는 경향(傾向)이었으며 건삼(乾蔘), 미삼(尾蔘), 수삼(水蔘)의 순(順)으로 높은 함량(含量)을 보였다. 4. 총질소(總窒素) 함량(含量)은 수삼(水蔘), 건삼(乾蔘), 미삼(尾蔘)등에서 2.3$\sim$4.6% 내외로서 알콜함량(含量)이 증가(增加)함에 따라 수삼(水蔘)과 건삼(乾蔘)은 증가(增加)하였으나 건삼(尾蔘)은 감소(減少)하는 경향(傾向)이었고, 원삼별로(原料蔘別)로는 건삼(乾蔘), 수삼(水蔘), 미삼(尾蔘)의 순(順)으로 많은 함량(含量)을 보였다.ast and present culture of the area. Colored tiles and plant boxes attached to benches are introduced. The Dangsan park is a sacred space where modem people can feel the sacredness of nature arid of being in a refuge. Dangjib, Dangnamu, multi-purpose plaza, athletic facilities, and playground for infants are introduced. The Nature Street is a space for feeling and teaming nature which has disappeared from the area leading to the river and a space for community participation. The elementary school walls were demolished and nature education spaces, such as butterfly and dragonfly garden, ecological pond, wildflower garden, etc., which are related to school education, are introduced. The Ferry Space is a space symbolizing a old ferry crossing and an entrance plaza to a bridge for "Sunyu-do\" . A boat-shaped deck, an elevator for handicap people, and parking space are introduced. In conclusion, sustainable management

• Advances in aircraft and spacecraft science
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• 제7권4호
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• pp.371-385
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• 2020

A forward-facing aerospike attached to a payload fairing of a satellite launch vehicle significantly alters its flowfield and decreases the aerodynamic drag in transonic and low supersonic speeds. The present payload fairing is an axisymmetric configuration and consists of a blunt-nosed body along with a conical section, payload shroud, boat tail and followed by a booster. The main purpose of the present numerical simulations is to evaluate flowfield and assess the performance of aerodynamic drag coefficient with and without aerospike attached to a payload fairing of a typical satellite launch vehicle in freestream Mach number range 0.8 ≤ M_∞ ≤ 3.0 and freestream Reynolds number range 33.35 × 10⁶/m ≤ Re_∞ ≤ 46.75 × 10⁶/m whichincludes the maximum aerodynamic drag and maximum dynamic conditions during ascent flight trajectory of the satellite launch vehicle. A numerical simulation has been carried out to solve time-dependent compressible turbulent axisymmetric Reynolds-averaged Navier-Stokes equations. The closure of the system of equations is achieved using the Baldwin-Lomax turbulence model. The aerodynamic drag reduction mechanism is analysed employing numerical results such as velocity vector plots, density and Mach contours in conjunction with the experimental flow visualization pictures. The variations of wall pressure coefficient over the payload fairing with and without aerospike are exhibiting different kind of flowfield characteristics in the transonic and low supersonic speeds. The numerically computed results are compared with schlieren pictures, oil flow patterns and measured wall pressure distributions and exhibit good agreement between them.

• 한국자동차공학회논문집
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• 제25권2호
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• pp.207-218
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• 2017

Improving fuel consumption, particularly that of commercial vehicles, has become a global concern. The reduction in logistics cost has been a key issue in efforts to improve fuel economy and efficiency of transportation equipment. Typical technologies for reducing reduce fuel usage include air resistance reduction technologies, tire rolling resistance technologies, and idle technologies among others. Air resistance technology is a highly effective method that can be easily applied in a short period. As with air resistance technology, several devices involving side skirt, boat tail and gap fairing have been developed based on an analytical 3-D modeling technique for reducing air resistance attributed to the vehicle configuration. The devices were on a 45 feet tractor-trailer and the emission test was done using PEMS equipment. Fuel economy was evaluated by introducing several devices to reduce outer air resistance. The test was conducted by changing the experimental method of SAE J1321 Joint TMC/SAE Fuel Consumption Test Procedure - Type II test. As a result, air resistance decreased by at least 15 % and fuel economy improved by at least 13 %. This study sought to reduce greenhouse gas and improve fuel economy by applying several devices to a test vehicle to lower air resistance.

• 한국항공우주학회지
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• 제49권1호
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• pp.41-52
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• 2021

발사체가 대기 중에서 상승 비행 시 공기역학적 현상에 기인한 음향하중을 받는데 천음속 영역에서 그 영향이 커진다. 본 연구에서는 천음속 조건에서 해머헤드 발사체 외부에 작용하는 음향하중을 ��-ω SST 난류모델 기반 IDDES 법으로 해석하여 시간 평균 압력계수, 표면 압력섭동, 압력섭동 파워 스펙트럼을 분석하고 가용한 풍동실험 데이터와 비교하였다. IDDES 결과의 격자 의존성을 검토하였으며, 난류 스케일 분해가 가능한 적절한 계산격자를 사용한 경우 천음속 헤머헤드 발사체의 특징적인 유동 현상인 페어링 어깨에서의 유동 박리와 박리 유동의 후방 동체 재 부착, 보트 테일 후방에서의 높은 압력섭동을 공학적으로 유의미한 정확도로 예측 가능함을 확인하였다.

• 한국수산과학회지
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• 제20권2호
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• pp.157-165
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• 1987

1960년 1월 16일 강원도 명주군 옥계면 금진삼리 앞 500m 해상에서 삼중자망으로 채포한 쪽지를 사용하여 선상에서 인공수정시킨 후 실험실로 운반 사육하면서 난발생과정 및 자치어의 형태에 대하여 관찰한 결과를 요약하면 다음과 같다. 수정란은 난경이 $2.28\~2.36\;mm$로서 담유백색을 띤 구형의 침성점착란이다. 수체내의 사육수온은 $7.5\~21.4^{\circ}C$ 범위였으며 수정후 725시간만에 부화하였다. 부화직후의 자어는 전장이 $6.0\~6.9mm$로서 머리와 몸통이 크며, 배지느러미가 변형된 흡반이 형성되어 있고 수많은 흑색소포가 머리와 몸통부분에 발달한다. 부화후 17일째의 자어를 전장이 9.1 mm이며 아가미구멍은 가슴지느러미 기저 윗부분을 제외하고는 융합되어 있고, 꼬리위에도 흑색소포가 나타난다. 부화후 31일째의 자어는 전장이 10.6mm로서 각 지느러미 기조수가 정수에 달하여 치어로 되며, 제1등지느러미 가시는 소실된다. 부화후 103일째의 치어는 전장이 $15.4\~17.5mm$ 이다.