• 대한조선학회논문집
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• 제54권3호
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• pp.215-226
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• 2017

This paper presents numerical results of the performance of a marin propeller in cavitating and non-cavitating flow conditions. The geometry and experimental validation data of the propeller are provided in Potsdam Propeller Test Case(PPTC) in the framework of the second International Symposium on Marine Propulsors 2011(SMP'11) workshop. The PPTC includes open water tests, velocity field measurements and cavitation tests. The present numerical analysis was carried out by using the Reynolds averaged Navier-Stokes(RANS) method on a wall-resolved grid ensuring a y+=1, where the SST k-${\omega}$ model was mainly used for turbulence closure. The influence of the turbulence model was investigated in the prediction of the wake field under a non-cavitating flow condition. The propeller tip vortex flows in both cavitating and non-cavitating conditions were captured through adaptation of additional grids. For the cavitation flows at three operation points, Schnerr-Sauer's cavitation model was used with a Volume-Of Fluid(VOF) approach to capture the two-phase flows. The present numerical results for the propeller wake and cavitation predictions including the open water performance showed a qualitatively reasonable agreement with the model test results.

• 대한조선학회논문집
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• 제53권4호
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• pp.266-274
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• 2016

Many researchers have been trying to improve the propulsion efficiency of a propeller. In this study, the numerical analysis is carried out for the POW(Propeller Open Water test) performance of a propeller equipped with an energy saving device called PHVC(Propeller Hub Vortex Control). PHVC is aimed to control the propeller hub vortex behind the propeller so that the rotational kinetic energy loss can be reduced. The unsteady Reynolds Averaged Navier-Stokes(URANS) equations are assumed as the governing flow equations and are solved by using a commercial CFD(Computational Fluid Dynamics) software, where SST k-ω model is selected for turbulence closure. The computed characteristic values, thrust, torque and propulsion efficiency coefficients for the target propeller with and without PHVC and the local flows in the propeller wake region are validated by the model test results of KRISO LCT(Large Cavitation Tunnel). It is concluded from the present numerical results that CFD can be a good promising method in the assessment of the hydrodynamic performance of PHVC in the design stage.

• 한국해양공학회지
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• 제23권4호
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• pp.47-51
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• 2009

Thrust is one of the important performance characteristics of an AUV. At the design stage, the resistance of an AUV at its maximum speed is estimated and then the thrust system is designed, including the propeller diameter, propeller rpm, driving system, and required power. However, it is not possible to be certain that the thrust system has been correctly designed until the AUV is launched and its speed is measured. If data from a propeller open-water test is available, the thrust and torque of the propeller at a certain speed can be estimated. In addition, if the motor's torque characteristics are available, the maximum speed saturated by the induced propeller torque can be estimated. In this paper, an easy technique for estimating the maximum speed of an AUV will be shown, even in a case where additional resistance is gained from appendages not considered at the design stage. Furthermore, the thrust performance changes by adjusting the diameter of the propeller can be easily investigated.

• 대한조선학회논문집
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• 제48권2호
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• pp.141-146
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• 2011

This study numerically carried out the propeller open water test(POW) by solving Navier-Stokes equations governing the three-dimensional unsteady incompressible viscous flow with the turbulence closure model of the ${\kappa}-{\omega}$ SST model. Numerical simulations are performed at various range of advance ratios. Corresponding to Reynolds numbers of $5.89{\times}105{\sim}6.47{\times}105$ based on free stream velocity and the chord length at 0.7 propeller radius. The present results give a good agreement with those of the experiment. The propeller induced vortical structures have been analyzed by visualizing the resultant vorticity. As the advance ratio increases, the magnitude and length of the resultant vorticity decrease significantly. As the main focus of present study, the numerical model to present the ($r-{\theta}$) plane-averaged resultant vorticity along the streamwise direction for various advance ratios has been suggested.

• 한국산학기술학회논문지
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• 제20권9호
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• pp.150-155
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• 2019

공동현상은 유체의 속도 변화에 의한 압력변화로 인해 유체 내에 빈 곳이 생기는 현상을 말한다. 고속의 액체유동에서 액체의 압력이 포화증기압 이하로 낮아져서 액체 내에 증기 기포가 발생하는 현상이다. 본 연구에서는 선박 및 해양플랜트 분야에서 사용되어지는 유체기기에 대해 CFD 유동해석을 이용하여 선박용 프로펠러의 단독성능 해석기법의 타당성 확보 및 공동에 따른 유동양상을 파악하기 위해 FLUENT를 이용하여 전진비를 증가시키며 3차원 해석을 수행하고 MOERI의 실험 데이터와 비교분석하였다. 대형 컨테이너선용 KP505프로펠러의 사양을 기준으로 전진비에 따른 해석의 결과 전진비 0.7~0.8 구간에서 효율은 60% 수준으로 가장 높게 확인되었다. 압력면과 흡입면의 차이로 추력이 발생되는 것을 확인하였고 프로펠러 표면보다는 이면부근에서 Bubble이 많이 생성될 것으로 추정되며 공동현상이 더 많이 발생할 것이라 추정되었다. 또한 전진비가 증가함에 따라 공동현상은 급격히 감소함을 알 수 있었다. 추력계수와 토크계수는 MOERI 실험값과 비교했을 때 비교적 유사한 결과를 나타내었으며 전진비 1을 제외하고 모두 5%이내의 차이를 나타내었다. 따라서, CFD로 프로펠러 단독 성능에 대한 평가가 가능함을 확인하였다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제9권5호
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• pp.369-373
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• 2004

In order to elucidate the possibility of artificial production of p. ferulae by solid-state culture, the optimization of culture conditions was carried out. When $NH_4H_2PO_4$ and $CaCO_3$ were used in the cultures using test tube with 30 g of Populus sawdust at $25^{\circ}C{\pm}1$ in the dark, the favored mycelial growth was observed with $1\%$ of $NH_4H_2PO_4$ and the production of polysaccharide was 7.85 mg/100 mg of mycelium with $1\%$ of $CaCO_3$. The mixtures of $80\%$ of Populus Sawdust and $20\%$ of rice bran at $60\%$ of water content were determined to be optimal for the production of fruiting bodies in the sawdust culture. When three treatments containing various ratios of garlic powder were conducted, yields of fruiting bodies were drasti[ally higher than those of Synthetic mixture without garlic powder The highest yield (143 g/bag) was obtained with $7\%$ garlic powder. The yield of synthetic mixture containing $7\%$ of garlic powder was $83\%$ higher than that of Sawdust culture. The reason why garlic powder did support growth was not clear but it is possible that garlic powder might contain effective components for the formation of fruiting body. The optimal synthetic mixture composition consisted of cotton seed $77\%$, lime $6.4\%,\;K_2HPO_4\;0.2\%,\;KH_2PO_4\;0.2\%,\;CaHPO_4\;0.2\%$, corn flour $4\%$, wheat flour $5\%$, and garlic pow-der $7\%$.