• Proceedings of the KSME Conference
• /
• 2001.06e
• /
• pp.474-481
• /
• 2001

This paper addresses a numerical method for predicting transient temperature distributions in the wall of a curved pipe subjected to internally thermal stratification flow. A simple and convenient numerical method of treating the unsteady conjugate heat transfer in the non-orthogonal coordinate systems is presented. The proposed method is implemented in a finite volume thermal-hydraulic computer code based on a cell-centered, non-staggered grid arrangement, the SIMPLEC algorithm, a higher-order bounded convection scheme, and the modified version of momentum interpolation method. Calculations are performed for the transient evolution of thermal stratification in two curved pipes, where the one has thick wall and the other has so thin wall that its presence can be negligible in the heat transfer analysis. The predicted results show that the thermally stratified flow and transient conjugate heat transfer in a curved pipe with a finite wall thickness can be satisfactorily analyzed by the present numerical method, and that the neglect of wall thickness in the prediction of pipe wall temperature distributions can provide unacceptably distorted results.

• 한국전산유체공학회:학술대회논문집
• /
• 2009.04a
• /
• pp.368-376
• /
• 2009

Studies on the effect of the wall-ion, wall-water, water-ion and ion-ion interaction on properties of water and ions in nano-channels have been performed through the use of different kinds of ions or different models of potential energy between wall-ion or wall-water. On this paper, we address the effect of water-wall interaction potential on the properties of confined aqueous solution by using the molecular dynamics (MD) simulations. As the interaction potential energies between water and wall we employed the models of the Weeks-Chandler-Andersen (WCA) and Lennard-Jones (LJ). On the MD simulations, 680 water molecules and 20 ions are included between uniformly charged plates that are separated by 2.6 nm. The water molecules are modeled by using the rigid SPC/E model (simple point charge/Extended) and the ions by the charged Lennard-Jones particle model. We compared the results obtained by using WCA potential with those by LJ potential. We also compared the results (e.g. ion density and electro-static potential distributions) in each of the above cases with those provided by solving the Poisson-Boltzmann equation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.10 no.4
• /
• pp.440-448
• /
• 1998

This paper considers the influence of circumferential wall heat conduction for the case of forced convection around a circular cylinder in cross flow of air. Keeping uniform heat generation from the inner surface of the cylinder in radial direction, heat is transferred by wall conduction in the circumferential direction due to the asymmetric nature of the temperature distribution of the cylinder and by convection around the perimeter of the cylinder. The wall conduction depends on conductivity of the cylinder and size of the cylinder radius and thickness and affects the local convective heat transfer rate significantly for geometrically similar surfaces and flow conditions. A nondimensional conjugation parameter K. (=k$_t$R/k$_w$b) has been used to characterize the effect of the circumferntial wall heat conduction. The small values of conjugation parameter K are found to be associated with large effect of wall conduction on the local convective heat transfer rate.

• Journal of computational fluids engineering
• /
• v.7 no.3
• /
• pp.35-43
• /
• 2002

This paper addresses a numerical method for predicting transient temperature distributions in the wall of a curved pipe subjected to internal laminar thermally-stratified flow. A simple and convenient numerical method of treating the unsteady conjugate heat transfer in non-orthogonal coordinate systems is presented. Numerical calculations are performed for the transient evolution of thermal stratification in two curved pipes, where one has thick wall and the other has so thin wall that its presence can be negligible in the heat transfer analysis. The predicted results show that the thermally stratified flow and transient conjugate heat transfer in a curved pipe with a finite wall thickness can be satisfactorily analyzed by the present numerical method, and that the neglect of wall thickness in the prediction of pipe wall temperature distributions can provide unacceptably distorted results for the cases of pipes with thick wall such as safety related-piping systems of nuclear power plant.

• Journal of Mechanical Science and Technology
• /
• v.15 no.5
• /
• pp.671-680
• /
• 2001

Boundary condition is one of the major factors to influence the numerical stability and solution accuracy in numerical analysis. One of the most important physical boundary conditions in the flowfield analysis is the wall boundary condition imposed on the body surface. To solve a two-dimensional Euler equation, totally four numerical wall boundary conditions should be prescribed. Two of them are supplied by the flow tangency condition. The other two conditions, therefore, should be prepared additionally in a suitable way. In this paper, four different sets of wall boundary conditions are proposed and then applied to solve high-speed flowfields around a quarter circle geometry. A two-dimensional compressible Euler solver is prepared based on the finite volume method. This solver hires three different upwind schemes; Steger-Warmings flux vector splitting, Roes flux difference splitting, and Lious advection upstream splitting method. It is found that the way to specify the additional numerical wall boundary conditions strongly affects the overall stability and accuracy of the upwind schemes in high-speed flow calculation. The optimal wall boundary conditions should be also chosen very carefully depending on the numerical schemes used to solve the problem.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.27 no.1
• /
• pp.8-17
• /
• 2003

Fracture behaviors of pipes with local wall thinning are very important for the integrity of nuclear Power Plant. In Pipes of energy Plants, sometimes, the local wall thinning may result from severe erosion-corrosion (E/C) damage. However, the effects of local wall thinning on strength and fracture behaviors of piping system were not well studied. In this paper, the monotonic bending tests were performed of full-scale carbon steel pipes with local wall thinning. A monotonic bending load was applied to straight pipe specimens by four-point loading at ambient temperature without internal pressure. From the tests, fracture behaviors and fracture strength of locally thinned pipe were manifested systematically. The observed failure modes were divided into four types; ovalization. crack initiation/growth after ovalization, local buckling and crack initiation/growth after local buckling. Also, the strength and the allowable limit of piping system with local wall thinning were evaluated.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.120-125
• /
• 2007

Put Abstract text here The strain distribution measurement for wall thinned pipe bends by ESPI is presented. Defect types observed in the steel piping in the nuclear power plants (NPP) are the crack at the weld part and the wall thinning defect in the pipe bends. Especially, the wall thinning defects in the pipe bends due to the flow-accelerated corrosion (FAC) is a main type of defects observed in the carbon steel piping system. ESPI is one of the optical non-destructive testing methods and can measure the stress and the strain distribution of the object subjected by the tensile loading or the internal pressure. In this paper, the strain distribution of the wall thinned pipe bends due to the internal pressure will be measured by ESPI technique and the results are discussed. From the results, the size of the wall thinning defect can also be measured approximately.

• Earthquakes and Structures
• /
• v.8 no.5
• /
• pp.1147-1170
• /
• 2015

In this paper, the behavior of underground strutted retaining structure under seismic condition in non-liquefiable dry cohesionless soil is analyzed numerically. The numerical model is validated against the published results obtained from a study on embedded cantilever retaining wall under seismic condition. The validated model is used to investigate the difference between the static and seismic response of the structure in terms of four design parameters, e.g., support member or strut force, wall moment, lateral wall deflection and ground surface displacement. It is found that among the different design parameters, the one which is mostly affected by the earthquake force is wall deflection and the least affected is the strut force. To get the best possible results under seismic condition, the embedment depth of the wall and thickness of the wall can be chosen as around 100% and 6% of the depth of final excavation level, respectively. The stiffness of the strut may also be chosen as $5{\times}105kN/m/m$ to achieve best possible performance under seismic condition.

• Journal of the Korea Institute of Building Construction
• /
• v.9 no.1
• /
• pp.57-64
• /
• 2009

CWS I method developed to overcome the problems of frequent occurrence in the application of existing downward construction methods has demonstrated excellent efficiency. However, in the case of using slurry wall instead of SCW or CIP as a retaining wall, the improvements in connecting steel beams with the wall were demanded. Therefore, the study of CWS II method was carried out in order to accomplish the CWS I method reflecting its strong points and to ensure the settlement of a steel beam and to induce the diaphragm effect of a slab while reducing the degree of difficulty and the term of works and the cost of construction. In this paper, the concept and features of CWS II method as well as the progress of execution was discussed by comparing with existing methods.

• Journal of Construction Engineering and Project Management
• /
• v.7 no.1
• /
• pp.37-49
• /
• 2017

The Jinshanling section of the Great Wall of China is a series of fortifications in northern China that was constructed for strategic military defenses. This section was first built in the beginning of the Ming Dynasty in AD 1368 and then underwent major construction, reconstruction and renovation during the late Ming Dynasty, approximately in AD 1569. The Jinshanling section is 10.5 km long, a very short section compared with the entire 21,200 km wall. The wall section is located in Luanping County, Hebei province, China. This research paper focuses on the construction methods and materials of the wall and the towers in the area. The research methodology includes site visits, knowledge acquisition of experts and 3D graphic modeling. This study reveals that the materials selected for the structure include rubbles and rammed earth, bricks, stones, timber, and mortar. The erection sequence of the wall and the towers was a bottom-up fashion using various ancient construction techniques, such as the fire-setting rock blasting techniques and the surveying techniques from the Sea Island Mathematical Manual.