• 한국해양공학회지
• /
• 제23권6호
• /
• pp.12-16
• /
• 2009

In this study, the wave profiles and kinematics of highly nonlinear waves at various water depths were calculated using a 2D fully nonlinear Numerical Wave Tank (NWT). The NWT was developed based on the Boundary Element Method (BEM) with the potential theory and the mixed Eulerian-Lagrangian (MEL) time marching scheme by 4th-order Runge-Kutta time integration. The spatial variation of intermediate-depth waves along the direction of wave propagation was caused by the unintended generation of 2nd-order free waves, which were originally investigated both theoretically and experimentally by Goda (1998). These free waves were induced by the mismatch between the linear motion of wave maker and nonlinear displacement of water particles adjacent to the maker. When the 2nd-order wave maker motion was applied, the spatial modulation of the waves caused by the free waves was not observed. The respective magnitudes of the nonlinear wave components for various water depths were compared. It was found that the high-order wave components greatly increase as the water depth decreases. The wave kinematics at various locations were calculated and compared with the linear and the Stokes 2nd-order theories.

• Membrane and Water Treatment
• /
• 제10권1호
• /
• pp.57-65
• /
• 2019

This study assessed the contribution of emergent vegetation (Phragmites australis, Typha latifolia, and Nelumbo nucifera) to the submerged surface area, the amount of biofilms attached to the submerged portions of the plants, and the treatment performance of a free water surface (FWS) constructed wetland. Results showed that a 1% increase ($31m^2$) in the vegetative area resulted in an increase of $220m^2$ of submerged surface area, and 0.48 kg Volatile Suspended Solids (VSS) of attached biofilm. As the vegetation coverage increased, effluent organic matter and total Kjeldahl nitrogen decreased. Conversely, a higher nitrate concentration was found in the effluent as a result of increased nitrification and incomplete denitrification, which was limited by the availability of a carbon source. In addition, a larger vegetation coverage resulted in a higher phosphorus in the effluent, most likely released from senescent biofilms and sediments, which resulted from the partial suppression of algal growth. Based on the results, it was recommended that constructed wetlands should be operated with a vegetation coverage of just under 50% to maximize pollutant removal.

• 한국컴퓨터그래픽스학회논문지
• /
• 제23권1호
• /
• pp.17-24
• /
• 2017

미시적인 관점에서 물표면 주위에 위치한 물 입자와 공기 입자는 끊임없이 서로 상호작용을 한다. 이러한 상호작용은 대량의 작은 물 입자들이 엷게 흩날리는 상황이 표현되는 폭포나 바다에서 명확하게 나타난다. 즉, 엷게 퍼진 작은 물 입자들로 인해 물과 공기사이의 표면경계가 불분명해지며 이 부분에서 공기와 물 입자간의 상호작용으로 인해 급격한 와류현상이 나타나게 된다. 그러나 기존 입자 기반 물 시뮬레이션에서는 유동에 의해 나타나는 자기와류 (self-trubulent)에만 집중하였고, 자유표면 근처에서 공기에 의해 표현되는 부차적인 와류 현상에 대해서는 고려하지 못했다. 유체표면의 움직임에 집중된 모델링으로 인해 대량의 작은 물 입자들이 엷게 흩날리는 장면을 사실적으로 연출하기에는 한계가 있다. 우리는 1) 물 표면에서 공기의 역할을 담당하는 공기 입자 층을 적응적으로 생성하고, 2) 물과 공기를 서로 다른 상 (phase)으로 모델링하여 자유표면 근처에서 발생하는 와류를 사실적으로 표현하는 기법을 제안한다. 결과적으로, 우리는 공기에 의해 표현되는 와류를 입자기반 프레임워크에서 효율적으로 다루어 계산속도 및 결과측면에서 기존기법보다 개선된 결과를 얻었다.

• 한국농림기상학회지
• /
• 제7권1호
• /
• pp.91-97
• /
• 2005

BYL-EV250 증발기록계를 이용하여 해남 농경지역의 자유 수면 증발량을 관측하였고, 그 자료를 분석하여, 기상 요소와 증발량과의 관계를 분석하였다. 자연상태에서 증발량을 결정하는 기상요소의 관계를 살펴보고, 그 결과를 바람과 포차의 경험식으로 나타내었다. 이 식을 이용하여 자유 수면으로부터의 시간당 증발량을 구할 수 있었으며 수온, 기온, 습도, 풍속 같은 기상요소만으로 증발량 추정이 가능했다. 증발량 산출에 대한 신뢰성을 높이기 위해 지속적으로 수면에서의 물수지에 대한 연구가 수행되어야 할 것으로 사료된다. 증발량 관측도 다른 기상요소와 같이 매시간 관측 자료 생산 가능성을 시사했다. 부력을 이용한 측정방법은 미소 수위 변화(0.1mm 이하)를 측정 할 수 있어 대형증발계를 활용한 자동관측에 대한 신뢰성을 확보할 수 있었다. 이 결과를 바탕으로 장기간 관측된 자유수면 증발자료와 플럭스 타워에서 동시에 관측된 실제 증발산 자료의 비교분석이 현재진행 중에 있다.

• 대한가정학회지
• /
• 제19권1호
• /
• pp.25-31
• /
• 1981

The changes of various nitrogenfractions and free amino acid composition were investigated at various growing stages. The results are summarized as follows 1) Total nitrogen, water soluble protein nitrogen, and true protein nitrogen were decreased with growth. 2) Free amino acid increased with sprout-growth. the content of free amino acid were about 74.4%(combined Ser, Asp, Arg, Val) after 4 day sprout. It is belived that serine, aspartic acid, arginine and valine play an important role as taste compounds in mungbean sprout. 3) 16kinds of amino acid, including essential amino acids in human nutrition except tryptophan and cystin were quantified.

• 대한추나의학회지
• /
• 제1권1호
• /
• pp.83-90
• /
• 2000

Oryeong-San, Pangpungtongseong-San, Rangkyeoksanwha-Tang, Sipeemikwanjoong -Tang and Taeumjoui-Tang are not only examined using the code which are related to overweight in the QRIS but are also investigated the level of Free Radical using the Free Radical Measurement after steeping those 5 prescriptions in water. The results are as follows: 1. We indicated in the study of QRIS that 5 kinds of medicines which used most frequently In the treatment of the obesity appeared to affect the Immune system, spleen, kidneys, pancreas, the fatigue toxicity, TSH, and the metabolic disability but did not influence high on the contents of overweight and those of fatty cell, as well. in addition, there were no significant differences between the prescriptions as regards testosterone and progesterone. 2. In the Free Radical Measurement, Rangkyeoksanwha-Tang evaluated significantly high level of Free Radical, whereas others appear to have the similar level of Free Radical. These findings suggest that the treatment of the obesity affects particular body parts with respect to the control of overweight, although those medicines are not related directly to the areas(such as fatty cell Code), it is possible that they influence on the cure for the obesity. Furthermore, they indicate that with soaking prescription, Free Radical is not produced as much as we expected.

• Journal of Hydrospace Technology
• /
• 제2권1호
• /
• pp.10-17
• /
• 1996

If a point impulse travels over free surface of water of finite depth, surface waves consist of divergent waves. The crestlines of those divergent waves are short and end on the cusp line if the impulse travels at a subcritical speed. But the crestlines become infinitely long and there are no cusps if the impulse travels at a supercritical speed.

• 한국전산유체공학회지
• /
• 제7권3호
• /
• pp.44-52
• /
• 2002

An analytic methodology was developed for free surface motions between liquid metal coolant and cover gas in order to calculate the phenomena of gas entrainment in hot pool surface through IHX EMP and reactor core. The methodology was setup by applying the first order VOF convection model to CFX4 general purpose fluid dynamics analysis code. The methodology was validated by applying it to an experimental apparatus designed for free surface motions of KALIMER reactor. The distributions of free surface calculated by the present methodology were almost coincident with the experimental data. The developed methodology was applied to the KALIMER reactor of full power operating condition. The shapes of the free surface were nearly uniform. From the results, it was found that the altitude of the free surface from the IHX inlet nozzle of KALIMER reactor is high enough not to affect to free surface motions of generating gas bubbles from the turbulent shear flows such as hydraulic jump and water falls.

• Journal of applied mathematics & informatics
• /
• 제18권1_2호
• /
• pp.171-182
• /
• 2005

An analysis of the non-homogeneous term involved in the free surface condition for second order wave diffraction on a pair of cylinders is presented. In the computations of the nonlinear loads on offshore structures, the most challenging task is the computation of the free surface integral. The main contribution to this integrand is due to the non-homogeneous term present in the free surface condition for second order scattered potential. In this paper, the free surface condition for the second order scattered potential is derived. Under the assumption of large spacing between the two cylinders, waves scattered by one cylinder may be replaced in the vicinity of the other cylinder by equivalent plane waves together with non-planner correction terms. Then solving a complex matrix equation, the first order scattered potential is derived and since the free surface term for second order scattered potential can be expressed in terms of the first order potentials, the free surface term can be obtained using the knowledge of first order potentials only.

• 한국가시화정보학회지
• /
• 제20권2호
• /
• pp.55-62
• /
• 2022

We experimentally investigate a rising toroidal bubble impacting a free surface. The toroidal bubble is created by releasing pulsed air. By adjusting the volume and circulation of the toroidal bubble, the characteristics of interactions between the toroidal bubble and the free surface are identified. Because of the impact by the toroidal bubble, the free surface is convexly deformed upwards above the center point of the toroidal bubble, while the edge of the deformed free surface is pulled down. When the circulation of the bubble becomes stronger, the surface which was pulled down breaks eventually, and air above the free surface is entrained into water, forming an unstable toroidal bubble. The deformations at the center and edge of the free surface are in a linear relationship with the Froude number and the Weber number, respectively.