• 대한기계학회논문집
• /
• 제5권4호
• /
• pp.329-337
• /
• 1981

Natural convection within inclined high aspect-ratio rectangular cavity was analysed by using finite element method. For a cavity of sapect-ratio 20, the flow patterns of secondary vortices and the heat transfer characteristics on the wall were obtained with the variation of tilt angle as well as Ra and Pr. The observation on the governing equations shows that the increase of Ra/Pr and the existence of nonzero tilt angle make the flow pattern more complicated and so it becomes difficult to obtain converging solution. The max. value of Ra/Pr attained in this study was 3x10$\^$4/at 0$\^$0/ tilt angle and 1.1x10$\^$4/ at 45.deg. tilt angle for aspect ratio 20and Pr=0.7. Finally an empirical formula for Nusselt number which can accout for the effect of tilt angle is obtained for laminar flow regime.

• 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.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2005년도 춘계 학술대회논문집
• /
• pp.79-84
• /
• 2005

The numerical solutions are examined on the effect of a centered heat conducting body on natural convection in a 2-D square cavity. The influences of the Rayleigh number, the dimensionless conducting body size, and the ratio of the thermal diffusivity of the body to that of the fluid have been investigated on the natural convection heat transfer in overall concerned region. The analysis reveals that the fluid flow and heat transfer processes are governed by all of them. Results for isotherms, vector plots and wall Nusselt numbers are reported for Pr = 0.71 and relatively wide ranges of the other parameters. Heat transfer across the cavity, in comparison to that in the absence of a body, are enhanced (reduced) in general by a body with a thermal diffusivity ratio less (greater) than unity. The heat transfer are also found to attain a minimum as the body size is increased.

• Journal of applied mathematics & informatics
• /
• 제12권1_2호
• /
• pp.281-289
• /
• 2003

The convection of water is investigated in the vicinity of its density maximum temperature (277 K) in an inclined square cavity in the presence of heat sources. Numerical investigations are carried out by maintaining one of the vertical walls uniformly at 273 K and varying the other wall between temperatures 275 K and 285 K at different inclinations angles. The isotherms, streamlines and velocity profiles reveal the possible existence of multicellular fluid motions, and bidirectional velocity distributions. These fluid flow and heat transfer characteristics are significantly modified by the cavity inclination in the presence of heat sources.

• 한국전자파학회논문지
• /
• 제14권4호
• /
• pp.384-392
• /
• 2003

본 연구에서는 유전체 슬랩으로 덮힌 평행평판 도파관의 좁은 슬릿을 통한 유전체슬랩 위의 도체 스트립과의 전자기적인 결합을 고려하였다. 제안된 구조에서 관찰되는 두 가지의 대조적인 결합현상인 캐비티형 결합과 기생형 결합의 차이점을 도체 스트립의 길이 및 위치, 도체 스트립에 유기된 전류, 복사패턴, 대역폭, 결합슬릿 근처의 전자계분포 등을 비교하여 관찰하였다.

• Geomechanics and Engineering
• /
• 제20권2호
• /
• pp.147-154
• /
• 2020

A novel approach for predicting lateral displacement caused by pile installation in anisotropic clay is presented, on the basis of the cylindrical and spherical cavities expansion theory. The K₀-based modified Cam-clay (K₀-MCC) model is adopted for the K₀-consolidated clay and the process of pile installation is taken as the cavity expansion problem in undrained condition. The radial displacement of plastic region is obtained by combining the cavity wall boundary and the elastic-plastic (EP) boundary conditions. The predicted equations of lateral displacement during single pile and multi-pile installation are proposed, and the hydraulic fracture problem in the vicinity of the pile tip is investigated. The comparison between the lateral displacement obtained from the presented approach and the measured data from Chai et al. (2005) is carried out and shows a good agreement. It is suggested that the presented approach is a useful tool for the design of soft subsoil improvement resulting from the pile installation.

• 대한기계학회논문집A
• /
• 제20권8호
• /
• pp.2546-2554
• /
• 1996

In order to investigate the characteristics of sound-structure interaction problems, we modeled a rectangular cavity and the flexible wall of the cavity. Because the governing equations of motion are coupled through velocity terms, we could redefine them using the velocity potential. We calculated the natural frequencies of plate using orthogonal polynomial functions which satisfy the boundary conditions in the Rayleigh-Ritz Method. As the result, comparisons of theory and experiment show good agreement. and using orthogonal polynomial functions which satisfy the boundary conditions in the Rayleigh-Ritz method show useful method for sound-structure interaction problems too.

• 한국유체기계학회 논문집
• /
• 제2권3호
• /
• pp.52-58
• /
• 1999

The leakage and rotordynamic coefficients of see-through type gas labyrinth seals are determined using a two-control-volume-model analysis with Moody's wall-friction-factor formula which is defined with a large range of Reynolds number and relative roughness. Jet flow theory are used for the calculation of the recirculation velocity in the cavity. For the reaction force from the labyrinth seal, linearized zeroth-order and the first-order perturbation equations are developed for small motion about a centered position. The leakage and rotordynamic coefficient results of the present analysis are compared with Scharrer's theoretical analysis using Blasius' wall-friction-factor formula and Pelletti's experimental results. The comparison shows that the present analysis using Moody's wall-friction-factor formula and Scharrer's theoretical analysis using Blasius' wall-friction-factor formula give the same results for a smooth seal surface and the range of Reynolds number less than $10^5$.

• Earthquakes and Structures
• /
• 제10권4호
• /
• pp.811-828
• /
• 2016

This study aims to present nonlinear time history analysis results of double leaf cavity wall (DLCW) reinforced concrete structure exposed to shake table tests. Simulation of the model was done by a Finite Element (FE) program. Shake table experiment was performed at the National Civil Engineering Laboratory in Lisbon, Portugal. The results of the experiment were compared with numeric DLCW model and numeric model of reinforced concrete structure with unreinforced masonry wall (URM). Both DLCW and URM models have two bays and two stories. Dimensions of the tested structure and finite element models are 1:1.5 scaled according to Cauchy Froude similitude law. The URM model has no experimental results but the purpose is to compare their performance level with the DLCW model. Results of the analysis were compared with experimental response and were evaluated according to ASCE/SEI 41-06 code.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
• /
• pp.61-62
• /
• 2003

In this paper, the new higher order wall boundary conditions are proposed for solving the incompressible flows. The square driven cavity flows are simulated by using the variable order method of lines with the present wall boundary conditions. The variable order method of lines is constructed by the spatial discretization, i.e., the variable order proper convective scheme for convective terms and the modified differential quadrature method for diffusive terms, and time integration. The 2nd, 4th, and 6th order solutions are presented and these results show this higher order boundary conditions are very promising for the incompressible flow simulations.