Investigation of Flow Over Spillway Modeling and Comparison between Experimental Data and CFD Analysis

Serife Yurdagul Kumcu 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.3

As a part of design process for hydro-electric generating stations, hydraulic engineers typically conduct some form of model testing. The desired outcome from the testing can vary considerably depending on the specific situation, but often characteristics such as velocity patterns, discharge rating curves, water surface profiles, and pressures at various locations are measured. Due to recent advances in computational power and numerical techniques, it is now also possible to obtain much of this information through numerical modeling. In this paper, hydraulic characteristics of Kavsak Dam and Hydroelectric Power Plant (HEPP), which are under construction and built for producing energy in Turkey, were investigated experimentally by physical model studies. The 1/50-scaled physical model was used in conducting experiments. Flow depth, discharge and pressure data were recorded for different flow conditions. Serious modification was made on the original project with the experimental study. In order to evaluate the capability of the computational fluid dynamics on modeling spillway flow a comparative study was made by using results obtained from physical modeling and Computational Fluid Dynamics (CFD) simulation. A commercially available CFD program, which solves the Reynolds-averaged Navier-Stokes (RANS) equations, was used to model the numerical model setup by defining cells where the flow is partially or completely restricted in the computational space. Discharge rating curves, velocity patterns and pressures were used to compare the results of the physical model and the numerical model. It was shown that there is reasonably good agreement between the physical and numerical models in flow characteristics.

An Accurate Numerical Model Simulating Hysteretic Behavior of Reinforced Concrete Columns Irrespective of Types of Loading Protocols

Chang Seok Lee,Sang Whan Han 한국콘크리트학회 2021 International Journal of Concrete Structures and M Vol.15 No.1

In older reinforced concrete (RC) buildings, columns are fragile elements that can induce collapse of entire buildings during earthquakes. An accurate assessment of the seismic vulnerability of RC buildings using nonlinear response history analyses requires an accurate numerical model. The peak-oriented hysteretic rule is often used in existing numerical models to simulate the hysteretic behavior of RC members, with predefined backbone curves and cyclic deterioration. A monotonic backbone curve is commonly constructed from a cyclic envelope. Because cyclic envelope varies according to loading protocols, particularly in a softening branch, it is difficult to obtain a unique backbone curve irrespective of loading protocols. In addition, cyclic deterioration parameters irrespective of loading protocols cannot be found because these parameters are estimated with respect to the backbone curves. Modeling parameters of existing numerical models can also vary with respect to loading protocol. The objective of this study is to propose a loading protocol-independent numerical model that does not require estimates of modeling parameters specifically tuned for a certain loading protocol. The accuracy of the proposed model is verified by comparing the simulated and measured cyclic curves of different sets of identical RC column specimens under various loading protocols.

Comparison of Hoek-Brown and Mohr-Coulomb failure criterion for deep open coal mine slope stability

Cemalettin O. Aksoy,Guzin G. Uyar,Yılmaz Ozcelik 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.60 No.5

In deep open pit mines, slope stability is very important. Particularly, increasing the depths increase the risks in mines having weak rock mass. Blasting operations in this type of open pits may have a negative impact on slope stability. Several or combination of methods can be used in order to enable better analysis in this type of deep open-pit mines. Numerical modeling is one of these options. Many complex problems can be integrated into numerical methods at the same time and analysis, solutions can be performed on a single model. Rock failure criterions and rock models are used in numerical modeling. Hoek-Brown and Mohr-Coulomb terms are the two most commonly used rock failure conditions. In this study, mine planning and discontinuity conditions of a lignite mine facing two big landslides previously, has been investigated. Moreover, the presence of some damage before starting the study was identified in surrounding structures. The primary research of this study is on slope study. In slope stability analysis, numerical modeling methods with Hoek-Brown and Mohr-Coulomb failure criterions were used separately. Preparing the input data to the numerical model, the outcomes of patented-blast vibration minimization method, developed by co-author was used. The analysis showed that, the model prepared by applying Hoek- Brown failure criterion, failed in the stage of 10. However, the model prepared by using Mohr-Coulomb failure criterion did not fail even in the stage 17. Examining the full research field, there has been ongoing production in this mine without any failure and damage to surface structures.

불투과 잠제 전면에서 파랑 작용 하의 세굴 해석을 위한 수치모델의 개발

허동수(Hur,Dong-Soo),전호성(Jeon,Ho-Seong) 대한토목학회 2011 대한토목학회논문집 B Vol.31 No.5B

본 연구에서는 잠제 주변의 세굴 및 퇴적현상을 수치적으로 모의하기 위해 기존의 수치 파동 모델에 모래입자의 거동 해석을 위한 lagrangian 입자 모델을 결합한 새로운 수치모델을 개발하였다. 수치 피동 모델로서는 파랑에 의한 해저지반 내의 모래입자의 이동과 유동화 해석을 위해 투수성 매체 내부의 유체저항(관성저항, 층류저항 및 난류저항)을 고려할 수 있는 수치모델에 LES 난류모델을 도입한 수치해석기법(허와 최, 2008)을 이용하였다. 또한, 모래입자의 이동해석을 위한 lagrangian 입자 모델로서는 많은 개개의 입자들의 동적해석에 탁월한 개별요소법(Cundall and Strack, 1979)을 적용하였다. 개발된 해석기법을 이용하여 불투과 잠제 전면의 세굴에 대한 수치시뮬레이션을 실시한 후, 기존의 수리모형실험과 정성적으로 비교하면서 그 적용성을 검토하였다. In this study, the coupled-numerical model has been newly developed to investigate numerically scouring and deposition around a coastal structure like a submerged breakwater using a numerical wave model and a lagrangian particle model for sand transport. As a numerical wave model, LES-WASS-2D (Hur and Choi, 2008) is adopted. The model is able to consider the flow through a porous midium with inertial, laminar and turbulent resistance term and determine the eddy viscosity with LES turbulence model. Distinct element method (Cundall and Strack, 1979), which is able to apply to many dynamical analysis of particulate media, as a lagrangian particle model for sand transport is newly coupled to the numerical wave model. The numerical simulation has been carried out to examine the scour problem in front of an impermeable submerged breakwater using the newly coupled-numerical model. The numerical results has been compared qualitatively with an existing experimental data and then its applicability has been discussed.

3D Modeling of a Fabric based on its 3D Microstructure Image and Application of the Model of the Numerical Simulation of Heat Transfer

( Hyojeong Lee ),( Heeran Lee ),( Ran-i Eom ),( Yejin Lee ) 한국패션비즈니스학회 2016 패션 비즈니스 Vol.20 No.3

The objective of this study was to perform 3D solid modeling from 3D scanned surface images of cotton and silk in order to calculate the thermal heat transfer responses using numerical simulations. Continuing from the previous methodology, which provided 3D surface data for a fabric through optical measurements of the fabric microstructure, a simplified 3D solid model, containing a defined unit cell, pattern unit and fabric structure, was prepared. The loft method was used for 3D solid-model generation, and heat transfer calculations, made for the fabric, were then carried out using the 3D solid model. As a result, comprehensive protocols for 3D solid-model generation were established based on the optical measurements of real fabric samples. This method provides an effective means of using 3D information for building 3D models of actual fabrics and applying the model in numerical simulations. The developed process can be used as the basis for other analogous research areas to investigate the physical characteristics of any fabrics.

Monte Carlo 방법을 이용한 소구경용 밀도 존데의 반응 특성

원병호 ( Byeong Ho Won ),황세호 ( Seho Hwang ),신제현 ( Jeh Yun Shin ),박창제 ( Chang Je Park ),김종만 ( Jong Man Kim ),함세영 ( Se Yeong Hamm ) 한국지구물리·물리탐사학회 2014 지구물리와 물리탐사 Vol.17 No.3

MCNP를 이용한 밀도검층에 대한 수치모델링을 수행하였고, 인공 모형 시추공에 대한 교정곡선과의 비교를 통하여 MCNP 수치모델링의 신뢰성을 검토하였다. 이를 바탕으로 케이싱의 유무와 종류, 공내수의 유무, 존데와 공벽과의 거리 변화 등 국내 물리검층 자료 취득 현장에서 쉽게 접하는 3인치 시추공 환경에 대한 밀도검층 수치모델링을 수행하였다. 수치모델링 결과는 케이싱과 공내수의 영향을 정량적으로 반영하고 있으며 공벽으로부터의 간격 변화에 따른 일정한양상을 보여준다. 본 연구를 통하여 MCNP를 이용한 수치모델링의 적용성을 파악할 수 있었으며 이를 활용하여 효과적인 검층 보정이 가능할 것으로 판단된다. We performed MCNP modeling for density log, and examined its reliability and validity comparing the correction curves from physical borehole model. Based on the constructed numerical model, numerical modelings of density sonde in three-inch borehole were carried out under the various conditions such as the existence and type of casing or fluid, and also the stand-off between the sonde and borehole wall. These results of numerical modeling quantitatively reflect effects of casing and fluid in borehole, and moreover, demonstrate constant patterns with interval change from borehole wall. From this study, numerical modeling using MCNP shows a good applicability for well logging, and therefore, can be efficiently used for the calibration of well logging data under the various borehole conditions.

Development for Numerical Thermodynamic Modeling of a Reciprocating Air Compressor in Vehicle Air Suspension System

Hao Liu,Jaecheon Lee 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11

The research aim of the paper is to develop the numerical thermodynamic model for a reciprocating air compressor of the vehicle air suspension system. According to the reciprocating air compressor structure, volume variation inside the cylinder, intake air temperature, four different periods in each air compression cycle and heat transfer of the heat sink are analyzed in modeling. The numerical model of compression process as well as temperature variation of the air compressor heat sink is constructed in the condition that the air compressor continuously charges air into a tank. By using the thermodynamic model presented, the numerical simulation results indicate that the developed model can correctly describe the working process of the reciprocating air compressor.

수치모형을 이용한 고리형 수위-유량 관계 분석

김지성(Kim Ji Sung),김원(Kim Won),김동구(Kim Dong Gu),김치영(Kim Chi Young) 대한토목학회 2009 대한토목학회논문집 B Vol.29 No.1B

본 연구에서는 일반적으로 유량 자료의 생산을 위해 널리 사용되는 수위-유량관계의 고리형 특성 분석과 수치모형에 의해 이를 재현하는 것을 목적으로 하고 있다. 팔당대교 등 3개 지점의 연속적인 수위와 유량자료를 분석한 결과 여러 사상에서 매우 강한 고리형 특성이 발생하는 것을 확인하였다. 이는 기존 단일 수위-유량관계가 많은 오차를 포함할 수 있다는 것을 나타낸다고 할 수 있다. 한강 본류부에 일차원 수치모형을 이용하여 다양한 홍수사상에 적용하고, 그 결과를 실측 수위와 비교하여 검증하였다. 특히 2007년 홍수사상의 경우, 한강대교에 설치된 ADVM을 이용한 연속적인 유량측정 자료와 비교하여 수치모형에 의한 간접유량 산정의 적용성을 검증하였다. 검증된 수치해석 결과로부터 주요지점의 수위-유량관계를 작성한 결과 실측치와 유사한 형태를 구할 수 있었는데, 적절히 보정되고 검증된 수치모형을 이용하면 고리형 특성이 매우 강한 수위-유량관계의 재현이 가능함을 분석하였다. 본 연구 결과는 기존 단일 수위-유량관계의 오차 분석과 수치모형을 이용한 고리형 수위-유량관계 개발에 기여할 수 있을 것으로 판단된다. This study is focused on the analysis of loop characteristics of stage-discharge relation which is widely used for the production of discharge data and the simulation of loop stage-discharge relation using the numerical model. Analysis of consecutive stage and discharge data at 3 points revealed that loop of stage-discharge relationship is very strong. This means that the existing single stage-discharge relation may include large amount of error. Various flood events are simulated in mainstream of Han river with one-dimensional numerical model. The calculated stage data are compared with measured data. Especially continuous field-flow measurements concurrently collected with an Acoustic Doppler Velocity Meter (ADVM) on Hangang bridge in the case of 2007 flood event are used to verify the model applicability of estimating flows in open channels. This comparison shows that numerical model is an accurate and reliable alternative for making the real stage-discharge relation. Simulation of stage-discharge relation by a numerical model at Paldang and Hangang bridge showed good agreements with measured one, so it may be possible to generate real loop stage-discharge relation with properly calibrated and verified numerical model. It can be concluded that results of this study can contribute to error analysis of conventional single stage-dis-charge relation and development of loop stage-discharge relation with numerical model.

Eulerian-Granular method를 사용한 고체 입자 유동 모델 개발

이태규(T. G. Lee),신승원(S. W. Shin) 한국전산유체공학회 2015 한국전산유체공학회지 Vol.20 No.2

In this paper, we have developed numerical model for particulated flow through narrow slit using Eulerian-Granular method. Commercial software (FLUENT) was utilized as simulation tool and main focus was to identify the effect from various numerical options for modeling of solid particles as continuos phase in granular flow. Gidaspow model was chosen as basic model for solid viscosity and drag model. And lun-et-al model was used as solid pressure and radial distribution model, respectively. Several other model options in FLUENT were tested considering the cross related effect. Mass flow rate of the particulate through the slit was measured to compare. Due to the high volume density of the stacked particulates above the slit, effect from various numerical options were not significant. The numerical results from basic model were also compared with experimental results and showed very good agreement. The effects from the characteristics of particles such as diameter, angle of internal friction, and collision coefficient were also analyzed for future design of velocity resistance layer in solar thermal absorber. Angle of internal friction was found to be the dominat variable for the particle mass flow rate considerably. More defined 3D model along with energy equation for complete solar thermal absorber design is currently underway.

3차원 수치모형을 이용한 댐 붕괴파 모의에 관한 연구

정우창,이진우,조용식 한국방재학회 2012 한국방재학회논문집 Vol.12 No.2

In this study, the simulation of the flood wave due to the dam failure is carried out using a three-dimensional numerical model. The applied numerical model is ANSYS CFX (Ver. 13.0) which is a commercial software developed by ANSYS Inc. This numerical model is applied to three different cases of hydraulic model experiments related to the analysis of the dam-break wave, and the results simulated from three-dimensional model are compared and analyzed with those from laboratory measurements and the two-dimensional numerical model. As results of comparison, the predicted results agree well with measured ones and are more slightly accurate than those from the two-dimensional numerical model. In particular, the peak water depth and its time agree almost accurately with measured ones. Therefore, we can expect that the three-dimensional numerical model applied in this study could be effectively applied to predict the peak water depth and its time after a dam failure. 본 연구에서는 3차원 수치모형을 이용하여 댐 붕괴파에 대한 모의를 수행하였다. 적용된 3차원 수치모형은 ANSYS Inc에서 개발한 ANSYS CFX (Ver. 13.0) 상용 프로그램이며, 댐 붕괴파의 전파양상 분석과 관련된 기존의 세 가지 수리모형실험에 대해 측정결과와 2차원 수치모형에 의한 결과와 비교 및 분석을 수행하였다. 비교 결과 3차원 수치모형은 2차원 수치모형에 비해 측정결과에 보다 따르는 경향을 나타냈으며, 특히 첨두수심과 발생시간은 거의 정확하게 일치하였다. 따라서 본연구에서 적용된 3차원 수치모형은 댐 붕괴에 따른 첨두수심 및 발생시간의 예측에 대해 효과적으로 적용될 수 있을 것으로기대된다.