• Title/Summary/Keyword: Shallow water effect

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Preliminary Analysis on Design Parameters and Application Effects of Surface Water Heat Exchanger (SWHE) (지표수 열교환기 설계 변수와 적용 효과에 대한 선행 분석)

  • Sohn, Byonghu
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
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    • v.12 no.3
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    • pp.24-32
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    • 2016
  • Commercial buildings and institutions are generally cooling-dominated and therefore reject more heat to a borehole ground heat exchanger (BHE) than they extract over the annual cycle. Shallow ponds can provide a cost-effective means to balance the thermal loads to the ground and to reduce the length of BHE. This paper presents the analysis results of the impact of design parameters on the length of SWHE pipe and its application effect on geothermal heat pump (GHP) system using BHE. In order to analysis, we applied ${\varepsilon}-NTU$ method on designing the length of SWHE pipe. Analysis results show that the required pipe length of SWHE was decreased with the increase of approach temperature difference and with the decrease of pipe wall thickness. In addition, when the SWHE was applied to the GHP system, the temperature of BHE was more stable than that of standalone BHE system.

Deformation of Non-linear Dispersive Wave over the Submerged Structure (해저구조물에 대한 비선형분산파의 변형)

  • Park, D.J.;Lee, J.W.
    • Journal of Korean Port Research
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    • v.12 no.1
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    • pp.75-86
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    • 1998
  • To design a coastal structure in the nearshore region, engineers must have means to estimate wave climate. Waves, approaching the surf zone from offshore, experience changes caused by combined effects of bathymetric variations, interference of man-made structure, and nonlinear interactions among wave trains. This paper has attempted to find out the effects of two of the more subtle phenomena involving nonlinear shallow water waves, amplitude dispersion and secondary wave generation. Boussinesq-type equations can be used to model the nonlinear transformation of surface waves in shallow water due to effect of shoaling, refraction, diffraction, and reflection. In this paper, generalized Boussinesq equations under the complex bottom condition is derived using the depth averaged velocity with the series expansion of the velocity potential as a product of powers of the depth of flow. A time stepping finite difference method is used to solve the derived equation. Numerical results are compared to hydraulic model results. The result with the non-linear dispersive wave equation can describe an interesting transformation a sinusoidal wave to one with a cnoidal aspect of a rapid degradation into modulated high frequency waves and transient secondary waves in an intermediate region. The amplitude dispersion of the primary wave crest results in a convex wave front after passing through the shoal and the secondary waves generated by the shoal diffracted in a radial manner into surrounding waters.

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Effect of Rainfall Patterns on the Response of Water Pressure and Slope Stability Within a Small Catchment: A Case Study in Jinbu-Myeon, South Korea

  • Viet, Tran The;Lee, Giha;Oh, Sewook;Kim, Minseok
    • Journal of the Korean GEO-environmental Society
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    • v.17 no.12
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    • pp.5-16
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    • 2016
  • This study aims to assess the influence of rainfall patterns on shallow landslides initiation. Doing so, five typical rainfall patterns with the same cumulative amount and intensity components comprising Advanced (A1 and A2), Centralized (C), and Delayed (D1 and D2) were designed based on a historical rainstorm event in Jinbu. Mt area. Those patterns were incorporated as the hydrological conditions into the Transient Rainfall Infiltration and Grid-based Regional Slope-stability Model (TRIGRS) to assess their influences on groundwater pressure and changes in the stability of the slope. The results revealed that not only the cumulative rainfall thresholds necessary to initiate landslides, but also the rate at which the factor of safety decreases and the time required to reach the critical state, are governed by rainfall patterns. The sooner the peak rainfall intensity, the smaller the cumulative rainfall threshold, and the shorter the time until landslide occurrence. Left-skewed patterns were found to have a greater effect on landslide initiation. Specifically, among five rainfalls, pattern (A1) produced the most critical state. The severity of response was followed by patterns A2, C, D1, and D2. Our conclusion is that rainfall patterns have a significant effect on the cumulative rainfall threshold, the build-up of groundwater pressure, and the occurrence of shallow landslides.

Theoretical Analysis of Linear Maneuvering Coefficients with Water Depth Effect (수심의 영향을 고려한 선형(線形) 조종성 계수의 이론적 해석)

  • In-Young Gong
    • Journal of the Society of Naval Architects of Korea
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    • v.31 no.3
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    • pp.47-58
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    • 1994
  • Theoretical calculations are carried out for the estimation of linear maneuvering coefficients of a ship moving in shallow water region. Hydrodynamic forces and moments acting on a maneuvering ship are modelled based on a slender body theory, from which integro-differential equation for the unknown inner stream velocity is derived. Numerical algorithms fur solving this equation are described in detail. By considering water depth effects in the mathematical model, variations of maneuvering coefficients with water depth are studied. Programs are developed according to this method and calculations are done for Mariner, Series 60 and Wigley hull forms. For the verification of the programs, calculated results are compared with some analytic solutions and with published experimental results, which show good agreements in spite of many assumptions included in the mathematical model. It is expected that this method can be used as a preliminary tool for the estimation of maneuverability coefficients of a ship in shallow water region at its initial design stage.

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Effect of Hysteresis on Soil-Water Characteristic Curve in Weathered Granite and Gneiss Soil Slopes during Rainfall Infiltration (풍화계열 사면의 불포화 함수특성곡선 이력이 강우 침투에 미치는 영향)

  • Shin, Gil-Ho;Park, Seong-Wan
    • Proceedings of the Korean Geotechical Society Conference
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    • 2006.03a
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    • pp.28-33
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    • 2006
  • Shallow failures of slopes in weathered soils are caused by infiltration due to prolonged rainfall. These failures are mainly triggered by the deepening of the wetting band accompanied by a decrease in suction induced by the water infiltration. In this paper, hysteresis on soil-water characteristic curve(SWCC) of granite and gneiss weathered soils are investigated using transient flow analysis respectively. Each case was subjected to artificial rainfall intensities and time duration depending on the laboratory-based drying and wetting processes. The results show that the unsaturated seepage on weathered slopes are very much affected by the initial suction of soils and unsaturated permeability of the soils. In addition, a granite weathered soil has a lower air-entry value, residual matric suction, and wetting front suction and less hysteresis loop than a gneiss weathered soil.

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Interference of Acoustic Signals Due to Internal Waves in Shallow Water

  • Na Young-Nam
    • Proceedings of the Acoustical Society of Korea Conference
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    • spring
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    • pp.189-197
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    • 1999
  • To investigate internal waves (IW) effect on acoustic wave propagation, m analysis is conducted on mode travel time and model simulation. Based on the thermistor string data, it can be shown that the thermocline depth variation may cause travel time difference as much as 4-10 ms between mode 1 and 2 over range 10 km. This travel time difference causes interference among modes and thus fluctuation from range-independent stratified ocean structure. In real situations, however, there exist additionally spatial variation of IW. Model simulation with all modes and simple IW shows clear responses of acoustic signals to IW, amplitude and phase fluctuation.

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Dynamic Centrifuge Tests for Evaluating the Earthquake Load of the Structure on Various Foundation Types (다양한 기초 형식에 따른 단자유도 구조물 지진하중 평가를 위한 동적 원심모형실험)

  • Ha, Jeong Gon;Jo, Seong Bae;Park, Heon Joon;Kim, Dong Kwan;Kim, Dong Soo
    • Journal of the Earthquake Engineering Society of Korea
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    • v.20 no.5
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    • pp.285-293
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    • 2016
  • Soil-foundation-structure interaction (SFSI) is one of the important issues in the seismic design for evaluating the exact behavior of the system. A seismic design of a structure can be more precise and economical, provided that the effect of SFSI is properly taken into account. In this study, a series of the dynamic centrifuge tests were performed to compare the seismic response of the single degree of freedom(SDOF) structure on the various types of the foundation. The shallow and pile foundations were made up of diverse mass and different conjunctive condition, respectively. The test specimen consisted of dry sand deposit, foundation, and SDOF structure in a centrifuge box. Several types of earthquake motions were sequentially applied to the test specimen from weak to strong intensity of them, which is known as a stage test. Results from the centrifuge tests showed that the seismic responses of the SDOF structure on the shallow foundation and disconnected pile foundation decreased by the foundation rocking. On the other hand, those on the connected pile foundation gradually increased with intensity of input motion. The allowable displacement of the foundation under the strong earthquake, the shallow and the disconnected pile foundation, have an advantage in dissipating the earthquake energy for the seismic design.

A Research for Computation of Bearing Capacity and Settlement of Foundation Considering Scale Effect in Weathered-granite Layer (화강풍화토에서 Scale Effect를 고려한 기초의 지지력 및 침하량 산정에 관한 연구)

  • 박용부;정형식
    • Journal of the Korean Geotechnical Society
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    • v.20 no.1
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    • pp.131-139
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    • 2004
  • When calculating bearing capacity and settlement of actual foundation from plate test result fur design and construction of shallow foundation, scale effect should be considered. But, adequate guide and test result of scale effect were not prepared yet in Korea. So, to analyze the relations of bearing capacity and settlement as the difference of loading plate sizes, model test and field loading test were performed with different loading plate on weathered-granite layer. Model tests were conducted with water content, compaction number, saturated unit weight and plate size(Dl5, 25cm) in soil-box$(2,000\times 2,000\times 1,000mm)$ formed soil layer. Field loading tests were carried out with diameters of loading plate$(D15, 25, 30, 40, 75\times 75, 140\times 210cm)$ on the same soil condition. Finally, we presented the prediction formula of bearing and settlement for computating scale offset in design of shallow foundation through result analysis of load test and numerical simulation on weathered soil and rock.

The Comparison of Grid Resolutions using EFDC in Saemangeum Reservoir (격자 해상도에 따른 EFDC의 새만금호 모의)

  • Shin, Yu-Ri;Jang, Jeongryeil;Choi, Jung-Hoon;Cho, Young Kweon
    • Journal of Korean Society on Water Environment
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    • v.28 no.5
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    • pp.646-656
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    • 2012
  • This study area was Saemangeum Reservoir in Korea and the applied model was Environmental Fluid Dynamics Code(EFDC). It was the same as the scenarios to the boundary and initial conditions except the resolutions of the model grids. The resolutions were about 800 and 2,000 cells. It was considered scenario 1 and 2. The model was performed to simulate the water temperature, salinity, water quality parameters such as dissolved oxygen(DO), chemical oxygen demand(COD), total nitrogen(T-N), and total phosphorus(T-P) at 2008. The simulation results of the two scenarios were reflected in the trend of observed data tolerably. However, water flow, water temperature, and salinity showed high confidence level at the scenario 1. The water quality items did not present high confidence level at the scenario 1 because which concept was considered to biochemical and physical processes. This result shows that grid resolution has an influence on the water transport and the effect is reflected directly shallow and narrow water area. But, the selection of grid resolution should be considered the purpose of model simulation and the process of target items.

Significance of Ground Water Movements in the Numerical Modelling of Tunnelling (터널해석에 있어 지하수 거동의 중요성)

  • 신종호
    • Proceedings of the Korean Geotechical Society Conference
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    • 2003.03a
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    • pp.257-264
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    • 2003
  • Tunnelling in water bearing soils influences the ground water regime. It has been indicated in the literature that the existence of ground water above a tunnel influences tunnel stability and the settlement profile. Only limited research, however, has been done on ground water movements around tunnels and their influence on tunnel performance. Time dependent soil behaviour can be caused by the changes of pore water pressure and/or the viscous properties of soil(creep) under the stress change resulting from the advance of the tunnel face. De Moor(1989) demonstrated that the time dependent deformations due to tunnelling are mainly the results of pore pressure dissipation and should be interpreted in terms of effective stress changes. Drainage into tunnels is governed by the permeability of the soil, the length of the drainage path and the hydraulic boundary conditions. The potential effect of lime dependent settlement in a shallow tunnel is likely to occur rapidly due to the short drainage path and possibly high coefficient of consolidation. Existing 2D modelling methods are not applicable to these tunnelling problems, as it is difficult to define empirical parameters. In this paper the time-based 2D modelling method is adopted to account for the three dimensional effect and time dependent behaviour during tunnel construction. The effect of coupling between the unloading procedure and consolidation during excavation is profoundly investigated with the method. It is pointed out that realistic modelling can be achieved by defining a proper permeability at the excavation boundary and prescribing appropriate time for excavation Some guidelines for the numerical modelling of drained and undrained excavation has been suggested using characteristic time factor. It is highlighted that certain range of the factor shows combined effect between the unloading procedure due to excavation and consolidation during construction.

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