HSVA 두 탱커 선형에 대한 점성유동 계산

곽영기(Young-ki Kwak) 한국해양공학회 1999 韓國海洋工學會誌 Vol.13 No.2

The viscous flow around a ship hull is calculated by the use of RANS (Reynolds-averaged Navier-Stokes) solver. Reynolds stresses are modelled by using the k-ε turbulence model and the law of wall is applied near the body. Body fitted coordinates are introduced for the treatment of the complex boundary of the ship hull form and the governing equations in the physical domain transformed into the ones in the computational domain. The transformed equations are numerically solved by an employment of FVM(Finite Volume Method). SIMPLE(Semi-Implicit Pressure Linked Equation) method is adopted in the calculation of pressure and the solution of the discretized equation is obtained by the line-by-line method with the use of TDMA(Tri-Diagonal Matrix Algorithme).<br/> To assure the propriety of this computing method, HSVA tanker and Dyne hull are calculated at both model and ship scale Reynolds number. Their results of pressure distributions on fore and aft body, axial velocity contours and transverse velocity vectors and viscous resistance coefficients are compared with other’s experiments and calculations.

수치해를 이용한 선박의 점성저항 해석

곽영기(Young-Ki Kwak) 한국해양공학회 1997 韓國海洋工學會誌 Vol.11 No.2

Viscous flow around an actual ship is calculated by an use of RANS(Reynolds-averaged Navier-Stokes) solver. Reynolds stress is modelled by using k-ε turbulence model and the law of wall is applied near the body. Body fitted coordinates are introduced for the treatment of the complex boundary of the ship hull form. The transformed equations in the computational domain are numerically solved by an employment of FVM(Finite Volume Method). SIMPLE(Semi-Implicit Pressure Linked Equation) method is adopted in the calculation of pressure and the solution of the discretized equation is obtained by the line-by-line method with the use of TDMA(Tri-Diagonal Matrix Algorithme).<br/> The subject ship model of actual calculation is 4,410 TEU class container carrier. For 4 geosim models the calculated viscous resistance values are compared with the model test results and analyzed on their components. The resistance performance of an actual ship is predicted very reasonably, so this method may be utilized as a design tool of hull form.

은나노 제품인 Pyto-patch의 제조공정 및 Pyto-patch의 고추 탄저병 방제효과

곽영기(Young-Ki Kwak),김성일(Seong-Il Kim),이종만(Jong-Man Lee),김일섭(Il-Seop Kim) (사)한국생물환경조절학회 2012 생물환경조절학회지 Vol.21 No.2

나노 크기인 5㎚ 이하로 제조한 은나노제품(파이투패치)은 주요 식물병원균인 탄저병원균(Collectotrichum gloeosporioides), 잿빛곰팡이병원균(Botrytis cinerea), 균핵병원균(Sclerotinia sclerotiorum)에 대해 포자발아 및 균사생장을 억제하는 항균력이 있었다. 파이투패치 살포에 의한 고추탄저병 방제효과를 실험하기 위해 파이투패치 희석액에 포자를 침지하여 포습시킨 후 발아율을 조사한 결과 5ppm까지 희석한 처리구에서 병원균의 포자발아억제효과를 보였으며, 균사는 10ppm에서 생장억제효과가 15일간 지속되었다. 특히 파이투패치를 10ppm으로 희석하여 배지표면에 도말한 후 탄저병원균 포자를 접종하면 3일간 발아가 억제되어 식물체 감염을 효과적으로 예방하였으며, 40% 이상 발병한 시험구에 4ppm 파이투패치를 살포한 결과 21일 후 7% 이하의 발병과율로 무처리 대비 70% 방제효과가 있었다. 장마철 탄저병 발생율이 94.6%인 시험포장에서 10ppm 농도로 파이투패치를 7일간격으로 엽면살포한 결과 발병과 발생율이 5.8%로 방제효과를 확인하였으며, 수확한 홍고추를 자연건조한후에도 발병과율이 24.2%로 건고추 수확량도 증가하였다. 장마철 고추역병(Phytophthora capsici)은 장마가 끝난 무피복시험구에서 8월 11일 15%이었으며 고온기를 지난 9월 7일에는 발병율이 74%로 수확을 포기하였으나, 파이투패치를 코팅처리한 피복재를 씌운 시험구에서는 발병주가 2.3%로 장마철 역병발생이 효과적으로 방제되었다. The commercial product “pyto-patch” prepared as nano sized silver particle less than 5 nm, has effective antifungal activity against Collectotrichum gloeosporioides, Botrytis cinerea, Sclerotinia sclerotiorum in vitro. As a fungal growth inhibiton mechanism, it can reduce spore germination rate and mycelial growth. As s promising fungicide, Phyto-patch can control anthracnose effectively. The spore of C. gloeosporioides dipped in 5 ppm phyto-patch dilute suppressed germination rate to 13.2%, and mycelial growth stopped for 15 days at 10 ppm. The spore postinoculated on 10 ppm phyto-path smeared PDA surface could not germinate for 3 days and prohibit pathogen infection effectively. In field test, the anthracnose development of 4 ppm phyto-patch treated plot was less than 7% after 21 days compaired to 40% of it in untreated plot. In heavy rainfall season, pepper anthracnose effectivly contrrolled by regular 10 ppm phytopatch spraying every 7 days. The diseased pepper fruit decreased to 5.8% compaired to 94.6% in untreated plot. During drying period, the diseased pepper fruit havested in phyto-patch treated plot was 24.2%, but pepper fruit havested in untreated plot destroyed to 100% within 3 days. The nano silver particle coated on multching textile prevented late blight of pepper effectively and disease occurance delayed about month.

친환경 유기농자재의 잿빛곰팡이병 병원균의 생장 억제 효과

곽영기(Young-Ki Kwak),김일섭(Il-Seop Kim),조명철(Myeong-Cheoul Cho),이성찬(Seong-Chan Lee),김수(Su Kim) (사)한국생물환경조절학회 2012 생물환경조절학회지 Vol.21 No.2

친환경 유기농자재를 이용하여 잿빛곰팡이병균의 포자 발아, 균사생장 억제효과를 기내에서 조사하였다. 그 결과 잿빛곰팡이병의 균사생장 억제 효과는 Bacillus subtilis를 주성분으로 하는 제제가 100%의 억제효과를 보였으며, 그 외의 제제는 20% 이하의 범위에서 억제효과를 나타내었다. 포자발아 억제효과는 유기황 수화제 2종(‘BTB’, ‘황스타’)이 각각 97.7%, 92.3%으로 나타났다. 균사생장 억제와 포자 발아억제에 모두 효과를 보이는 제제는 없었다. 따라서 잿빛곰팡이병 방제를 위해서는 포자발아 억제를 위한 방제와 균사생장억제를 위한 제제를 각각 처리하여야 할 것으로 사료되었다. 아울러 사물 기생성을 가진 잿빛곰팡이병의 방제를 위해서는 잔재물에서 생장을 막는 것이 중요하며 이를 위해 예방을 전제로 한 방제의 경우 유기황을 주성분으로 하는 제제가 적용 가능할 것으로 생각된다. Inhibition effects on spore germination and mycelia growth for gray mold (Botrytis cinerea) were investigated in vitro using environment-friendly agricultural materials as well as environment-friendly pesticides. The inhibition effect on mycelia growth of gray mold is the highest when the gray mold mycelia were treated with a pesticide (commercial name: Koreayeok, Jihabudea KM, Sootingtan, Sootingstar) that contains a mixture of Bacillus subtilis, resulting in 100% inhibition of the mycelia growth. Meanwhile, the range of less than 20% inhibition effects on the growth of gray mold mycelia was observed with other commercial agricultural materials. The significant inhibition effects on spore germination of gray mold fungus were shown in vitro with two water dispersible pesticides containing sulfur [BTB (97.7%) and SulfurStar (92.3%)], respectively. These in vitro results of inhibiting of the spore germination and mycelia growth together cannot found. It remains to be determined whether the selected environment-friendly agricultural materials in effective control of gray mold in vitro can be used to control gray mold in field.

친환경 유기 농자재의 고추 탄저병(Colletotrichum acutatum) 병원균의 생장 억제 효과

곽영기(Young-Ki Kwak),김일섭(Il-Seop Kim),조명철(Myeong-Cheoul Cho),이성찬(Seong-Chan Lee),김수(Su Kim) (사)한국생물환경조절학회 2012 생물환경조절학회지 Vol.21 No.2

친환경 유기농자재를 이용하여 고추 탄저병균의 포자 발아, 균사생장 억제효과를 기내에서 조사하였다. 그 결과 균사생장 억제효과 기내검정. 탄저병의 균사생장 억제 효과는 Bacillus subtilis를 주성분으로 하는 제제가 100%의 억제효과를 보였으며, 그 외의 제제는 20~40%의 범위에서 억제효과를 나타내었다. 포자발아억제효과는 유황 수화제 2종(‘BTB’, ‘황스타’)이 각각 100%, 95.1%, ‘고려역’(95.0%), ‘보르스타’(99.0%), ‘지하부대 KM’(96.1%) 순으로 나타났다. 균사생장 억제와 포자 발아억제, 부착기 형성억제 결과를 고려하여 고추 탄저병 방제에 적용 가능한 친환경 방제제는 Bacillus subtilis, Panibacillus polymyxa 혼용제(‘고려역’)가 가장 효과적인 것으로 판단되었으며, 예방을 전제로 한 방제의 경우 유황 수화제, 보르도액을 주성분으로 하는 제제가 적용 가능할 것으로 생각된다. 본 연구에서 선택된 제제는 고추 포장에서 탄저병 방제효과가 최종적으로 인정되면 차후 고추 탄저병 방제에 이용될 것으로 사료된다. Inhibition effects on spore germination and mycelia growth for pepper anthracnose fungi (Collectricum acutatum) were investigated in vitro using eco-friendly agricultural materials as well as ecofriendly pesticides. The inhibition effect on mycelia growth of anthracnose fungi is the highest when the anthracnose mycelia were treated with a pesticide (commercial name: Koreayeok) that contains a mixture of Bacillus subtilis and Panibacillus polymyxa, resulting in 100% inhibition of the mycelia growth. Meanwhile, the range of 20~40% inhibition effects on the growth of anthracnose mycelia was observed with other commercial agricultural materials. The significant inhibition effects on spore formation of anthracnose fungus were shown in vitro with two water dispersible pesticides containing sulfur [BTB (100%) and SulfurStar (95.1%)], Koreayeok (95.0%), Borstar (99.0%) containing Bordeaux mixture, and Jihabudea-KM containing Psedomonas spp. (96.1%), respectively. Taken from these in vitro results of inhibiting of the spore germination and mycelia growth together, Koreayeok is the most effective on control of pepper anthracnose disease in vitro. In addition, two water dispersible pesticides containing sulfur (BTB and SulfurStar) and Borstar (99.0%) containing Bordeaux mixture are also significantly applicable to prevent pepper plants from anthracnose disease in vitro. It remains to be determined whether the selected eco-friendly agricultural materials in effective control of anthracnose in vitro can be used to control pepper anthracnose in field.

등온적출곡선(等溫摘出曲線)에 의한 염산용액(鹽酸溶液)에서 TBP와 Alamine336의 철 추출(抽出) 비교(比較)

이만승,곽영기,Lee, Man-Seung,Kwak, Young-Ki 한국자원리싸이클링학회 2008 資源 리싸이클링 Vol.17 No.3

이온강도가 센 염산용액에서 Alamine336과 TBP에 의한 염화 제 2철의 용매추출거동을 MaCabe-Thiele도를 이용하여 비교하였다. 초기 추출조건으로부터 수상과 유기상에서 철의 평형농도를 계산하여 두 추출제에 의한 철 추출의 등온추출곡선을 구했다. 평형농도 계산시 수상에서 착물형성반응과 물질수지 및 추출반응을 고려하였다. 1M의 Aalmine336으로 0.5M의 철을 3M의 염산용액에서 수상과 유기상의 부피비가 6/5인 조건에서 추출시 2단에 철의 대부분이 유기상으로 추출되는 것을 MaCabe-Thiele도에서 알 수 있었다. 1M의 Alamine336은 염산용액에서 철의 추출능력면에서 TBP 2-3M과 비슷하였다. MaCabe-Thiele도와 두 추출제의 물리적 특성으로부터 Alamine336이 TBP보다 염산용액에서 철의 추출특성이 우수한 것을 알 수 있었다. Solvent extraction behaviors of iron(III) from chloride solution at high ionic strength condition between Alamine336 and TBP were compared by using MaCabe-Thiele diagram. Extraction isotherms of iron by the two extractants were obtained by calculating the equilibrium concentrations of iron in both phases from the initial extraction conditions. In calculating the equilibrium concentration of iron, chemical equilibria in the aqueous phase and mass balance together with the solvent extraction reaction were considered. MaCabe-Thiele diagram of iron by 1M Alamine336 indicated that two extraction stages could lead to complete extraction of 0.5M iron from 3M HCl solution at an A/O ratio of 6/5. The extraction power of 1M Alamine336 was found to be the same as 2-3M TBP. MaCabe-Thiele diagram together with the physical properties of the two extractants indicated that Alamine336 is superior to TBP in extracting ferric iron from chloride solution.

횡파 중 수중함 단면에 대한 운동 특성

이호영(HO-YOUNG LEE),곽영기(YOUNG-KI KWAK) 한국해양공학회 2005 韓國海洋工學會誌 Vol.19 No.5

The motion response results of a submerged submarine section in waves are presented. The numerical method is based on Cauchy's integral and 3 degrees-of-freedom motions of submarine sections are calculated in two dimensions, in regular waves. The fully nonlinear free surface and body boundary conditions are applied to the present problem, and the viscous effects on the submarine are modeled by Morison's formulas The motions of submarine sections in beam sea are directly simulated and the effects of wave frequency, snorkel depth, and bridge are discussed.

파랑중에서 전진하는 선박의 부가저항 해석

이호영(Ho-Young Lee),곽영기(Young-Ki Kwak) 한국해양공학회 1997 韓國海洋工學會誌 Vol.11 No.2

This paper presents theoretical formulations and numerical computations for predicting first-and second-order hydrodynamic forces on a ship advancing in waves. The theoretical formulation leads to linearized radiation and diffraction problems solving the three-dimensional Green function integral equations over the mean wetted body surface. Green function representing a translating and pulsating source potential for infinite water depth is used. In order to solve integral equations for three dimensional flows using Green function efficiently, the Hoff’s method is adopted for numerical calculation of the Green function. Based on the first-order solution, the mean seconder-order forces and moments are obtained by directly integrating second-order pressure. over the mean wetted body surface. The calculations are carried out for analyzing the seakeeping characteristics of Series 60. The calculated items are hydrodynamic coefficients, wave exciting forces, frequency response functions and added resistance in waves.

선박의 충돌로 인한 해양구조물의 거동 해석

이호영(HO-YOUNG LEE),박종환(JONG-HWAN PARK),곽영기(YOUNG-KI KWAK) 한국해양공학회 2001 韓國海洋工學會誌 Vol.15 No.4

The simulation of motion responses of a dolphin-moored ocean structure in shallow water when it cllides with a ship, has been carried out. The equation of motion in the time domain according to Cummin's theory is employed, and solved by making use of the Newmark-β method. The added mass and damping coefficients involved in the equations are obtained from a three-dimensional panel method in the frequency domain. The impact forces due to ship collision are calculated using both the elastic and non-elastic modelings. The mooring forces for dolphin systems of ocean structure are regarded as linear spring forces.

파랑에 의한 항만 내 부유체의 운동

이호영(HO-YOUNG LEE),곽영기(YOUNG-KI KWAK),박종환(JONG-HWAN PARK) 한국해양공학회 2006 韓國海洋工學會誌 Vol.20 No.2

As large waves enter a harbor, during their propagation, the motions of a floating body are large and it may even be damaged by waves.This phenomenon may be caused by harbor resonance, resulting from large motions at low wave frequency, which is close to the natural frequency of a vessel.In order to calculate the motions of a floating body in a harbor, it is necessary to use the wave forces containing the body-harbor interference.The simulation program to predict the motions of a floating body by waves in a harbor is developed, and this program is based on the method of velocity potential continuation method proposed by Ijima and Yoshida The calculated results are shown by the variation of wave frequency, wave angle, and the position of a floating body.