• International Journal of Contents
• /
• 제4권2호
• /
• pp.7-12
• /
• 2008

In this paper, we present a real-time physical simulation model of water surfaces with a novel method to represent the water mass flow in full three dimensions. In a physical simulation model, the state of the water surfaces is represented by a set of physical values, including height, velocity, and the gradient. The evolution of the velocity field in previous works is handled by a velocity solver based on the Navier-Stokes equations, which occurs as a result of the unevenness of the velocity propagation. In this paper, we integrate the principle of the mass conservation in a fluid of equilateral density to upgrade the height field from the unevenness, which in mathematical terms can be represented by the divergence operator. Thus the model generates waves induced by horizontal velocity, offering a simulation that puts forces added in all direction into account when calculating the values for height and velocity for the next frame. Other effects such as reflection off the boundaries, and interactions with floating objects are involved in our method. The implementation of our method demonstrates to run with fast speed scalable to real-time rates even for large simulation domains. Therefore, our model is appropriate for a real-time and large scale water surface simulation into which the animator wishes to visualize the global fluid flow as a main emphasis.

• 지구물리와물리탐사
• /
• 제13권4호
• /
• pp.330-335
• /
• 2010

시추공 주시 토모그래피에 의하여 도출된 속도 영상의 신뢰도 평가를 위하여 파선-속도격자의 결합도와 시스템 행렬의 역산 특성 분석에 대한 연구를 실시하였다. 분석 대상은 SIRT법에 의하여 도출된 속도 모델과 이를 도출한 초동 주시와 파선 정보이다. 파선-속도격자 결합도는 파선 밀도 즉 격자 당 투사 파선 수와 파선 선분들의 합으로 산출하였고, 도출된 속도모델의 분해능 및 불확실성에 대한 정보는 데이터 공간(초동주시)과 모델 공간(속도모델)을 관련짓는 시스템 행렬의 특이 값 분해로부터 도출하였다.

• Computers and Concrete
• /
• 제20권6호
• /
• pp.711-718
• /
• 2017

Nanotechnology is a new filed in concrete structures which can improve the mechanical properties of them in confronting to impact and blast. However, in this paper, a mathematical model is introduced for the concrete models subjected to impact load for wave propagation analysis. The structure is simulated by the sinusoidal shear deformation theory (SSDT) and the governing equations of the concrete model are derived by energy method and Hamilton's principle. The silicon dioxide ($SiO_2$) nanoparticles are used as reinforcement for the concrete model where the characteristics of the equivalent composite are determined using Mori-Tanaka approach. An exact solution is applied for obtaining the maximum velocity of the model. In order to validate the theoretical results, three square models with different impact point and Geophone situations are tested experimentally. The effect of different parameters such as $SiO_2$ nanoparticles volume percent, situation of the impact, length, width and thickness of the model as well as velocity, diameter and height of impactor are shown on the maximum velocity of the model. Results indicate that the theoretical and experimental dates are in a close agreement with each other. In addition, using from $SiO_2$ nanoparticles leads to increase in the stiffness and consequently maximum velocity of the model.

• 한국방재학회:학술대회논문집
• /
• 한국방재학회 2007년도 정기총회 및 학술발표대회
• /
• pp.140-143
• /
• 2007

A continuing elevated bridge is replaced with mass-spring system model, and a part of the bridge is cut out as an analytical area. A viscous boundary is installed at both ends, and dynamic analyses are carried out changing the wave velocity of the viscous boundary, The result is compared with a result of a very long model corresponding to the solution with infinite length. A wave velocity is chosen so that the good performance of a viscous boundary is exhibited. The parametric analyses are carried out changing the model of various structural properties, and an approximation expression is suggested to obtain the wave velocity easily for setting a viscous boundary.

• 한국군사과학기술학회지
• /
• 제16권5호
• /
• pp.639-645
• /
• 2013

The aim of the study is to investigate the method to estimate a storage life of propelling charge on the decrease of muzzle velocity by stochastic gamma process model. It is required to establish criterion for state failure to estimate the storage life and it is defined in this paper as a muzzle velocity difference between reference value and maximum allowable standard deviation multiplied by 6. The relationship between storage time and muzzle velocity is investigated by nonlinear regression analysis. The stochastic gamma process model is used to estimated the state distribution and the life distribution for storage time for 155mm propelling charge KM4A2 because the regression analysis is a deterministic method and it can't describe the distribution of life for storage time.

• Journal of Advanced Marine Engineering and Technology
• /
• 제25권6호
• /
• pp.1308-1316
• /
• 2001

This paper described a numerical investigation performed to understand better the effects of flow parameters in an entrained flow combustor on the flow characteristics. The computational model was based on the gas phase Eulerian equations of mass, momentum and energy. The code was formulated with RNG $k-\varepsilon$ model for turbulent flow. The calculation parameters were the ratio of primary and secondary jet velocity and the height difference between primary and secondary jet As the secondary jet velocity increased, the upper recirculation 3one of the primary jet was strengthened. It was found that as the primary jet velocity increased, there was a critical jet Velocity at which the size of upper and lower recirculation zone was reversed.

• 한국전산유체공학회지
• /
• 제7권4호
• /
• pp.8-18
• /
• 2002

The primary objective of the present study is evaluation of the k-ε-vv-f turbulence model for prediction of natural convection in a rectangular cavity. As a comparative study, the two-layer k-ε model is also considered. Both models, with and without algebraic heat flux model, are applied to the analysis of natural convection in a rectangular cavity. The performances of turbulence models are investigated through comparison with available experimental data. The predicted results of vertical velocity component, turbulent heat fluxes, turbulent shear stress, local Nusselt number and wall shear stress are compared with experimental data. It is shown that, among the turbulence models considered in the present study, the k-ε-vv-f model with an algebraic heat flux model predicts best the vertical mean velocity and velocity fluctuation, and the inclusion of algebraic heat flux model slightly improves the accuracy of results.

• 자원환경지질
• /
• 제35권5호
• /
• pp.445-454
• /
• 2002

본 연구에서는 지진 데이터를 이용한 지진 토모그래피 방법을 통해 남한 지역의 3차원 P파 속도모델을 구하였다. 구해진 3차원 속도모델은 정확한 진앙의 위치 결정과 한반도의 지하구조 연구에 이용될 수 있다. 3차원 속도모델을 구하기 위한 지진토모그래피 방법에서 보다 나은 역산 결과를 얻기 위해 초기모델로서 동시역산방법을 이용한 최소 1차원모델을 사용하였다. 최소 1차원모델의 속도는 0~l9 km사이는 6.04 km/s, 19~32 km차이는 6.45 km/s, 그리고 32~55 km사이는 7.78 km/s 였다. 최소 1차원모델을 초기값으로 하여 3차원 속도모델을 구해본 결과 1층(0~3 km) 에서는 경상분지, 영남육괴, 옥천습곡대에서 높은 속도값을 보이고, 경기육괴에서는 낮은 속도값을 보인다. 2층(3~19 km)에서 경상분지와 연일분지를 제외한 영남육괴 지역에서 높은 속도값이 분포한 반면, 경기육괴와 옥천습곡대에서 낮은 속도값이 분포한다. 3층(19~32 km)에서는 한반도 남부의 속도값은 높은 반면, 경기육괴 내의 SNU, YIN관측소를 제외한 대부분의 중부지역은 낮은 속도분포를 보인다. 4층(32 km)에서는 최대 속도값이 한반도의 중부와 남서부에, 최소 속도값이 남동부와 해안선에서 나타난다. 각 층의 깊이 분포는 중력자료에 의한 지각구조의 양상과 비교한 결과 서로 일치한다.

• Korean Chemical Engineering Research
• /
• 제55권5호
• /
• pp.698-703
• /
• 2017

Bubble flow characteristics in fluidized beds were analyzed by CPFD simulation. A fluidized bed, which had the size of $0.3m-ID{\times}2.4m-high$, was modeled by commercial CPFD $Barracuda^{(R)}$. Properties of bed material were $d_p=150{\mu}m$, ${\rho}_p=2,330kg/m^3$, and $U_{mf}=0.02m/s$. Gas was uniformly distributed and the range of superficial gas velocity was 0.07 to 0.16 m/s. Two other geometries were modeled. The first was a three-dimensional model, and the other was a two-dimensional model of $0.01m{\times}0.3m{\times}2.4m$. Bubble size and rising velocity were simulated by axial and radial position according to superficial gas velocity. In the case of three-dimensional model, simulated bubble rising velocity was different from correlations, because there was zigzag motion in bubble flow, and bubble detection was duplicated. To exclude zigzag motion of bubble flow, bubble rising velocity was simulated in the two-dimensional model and compared to the result from three-dimensional model.

• Nuclear Engineering and Technology
• /
• 제13권1호
• /
• pp.12-21
• /
• 1981

지난번 이미 다른곳에 발표한 재침수속도공식(rewetting velocity model)에 관한 논문을 더 확충하였다. 앞서 발표한 재침수속도 공식을 사용하려면 ø의 값을 미리 알고 있어야한다. ø값을 모를 때에는 film boiling 열전달계수 ( $h_{df}$ )와 fog-film길이 (ι)의 자료가 있어야 한다. 이러한 자료를 제공하기 위해서, 먼저 브롬리(Bromley)의 공식을 수정하여 보다 높은 압력조건하에서의 $h_{df}$ 값을 구하였다. 그리고, 지난번 사용한 자료보다 훨씬 더 충실한 PWR-FLECHT 자료를 사용하여 ø와 ι과 같은 precooling 계수들의 합을 더 확충하여 놓았다. 이리하여, 재침수속도공식의 응용 가능한 영역을 더 확대하였다.