Numerical Simulation on Variation Characteristics of Wave Field around Low-Crested Structure

In this study, we carried out the numerical simulation and analysis of the variation characteristics of the wave field around LCS (Low-Crested Structure), and the results were compared with the existing studies on submerged breakwater. Europe and Japan have conducted many researches on the LCS to prevent the beach erosion such that LCS has been regarded as an alternative to the submerged breakwaters. In addition, the research results were used for the design manuals. However, most conventional studies on LCS have been focused on the estimation of required weight of armor units with two-dimensional wave transmission, mainly based on experimental examinations and discussions. We conducted 2-D and 3-D numerical analysis for permeable LCS. In the study, we used the olaFlow model that is based on the Navier-Stokes momentum equations with the OpenFOAM®(Open source Field Operation And Manipulation) model. This model is a strongly nonlinear analysis method based on the finite volume method and it enables the breaking and turbulence analysis. First of all, we performed the verification of the olaFlow model. To this end, we compared the numerical results of the model to the existing experimental results in various aspects that include the wave variation around 2-D impermeable submerged breakwater, the water velocity around 2-D permeable submerged breakwater, the variation of seawater level and wave pressure around three-dimensional permeable upright walls, the variation of seawater level and flow velocity around three-dimensional impermeable submerged breakwater, and the generated wave profile and frequency spectrum of irregular wave. Then, we applied the model to LCS to carry out the numerical analysis of wave field characteristics in different cases such as (1) Variation Characteristic of Wave Field around 2-D LCS, (2) Variation Characteristics of Irregular Wave Fields around 2-D LCS, (3) Variation Characteristics of Wave Field around 3-D LCS, (4) Variation Characteristics of Irregular Wave Field around 3-D LCS. In case (1), experiments were carried out on the wave flume around the LCS with beach by changing the conditions like crest freeboard height, incident wave height and period. The variation characteristics such as the transmission by LCS, the wave propagation, the averaged wave height spatial distribution, the averaged water velocity and spatial distribution, and averaged turbulent kinetic energy were investigated. In case (2), we carried out experiments for the irregular wave field with additional analysis of characteristic of wave spectrum. In case (3) and (4), the experiments were conducted for 3-D numerical wave tank with the same cross section with case (1) and (2) by changing incident wave height, crest freeboard height, and structures gap width. Both the regular and irregular wave fields are studied, respectively. Variation characteristics and distribution of mean wave( wave) nearshore current as well as the mean turbulent kinetic were investigated compared with existing study results on submerged breakwater. |본 연구는 저천단구조물(LCS; Low-Crested Structure)의 주변에서 파동장의 변동특성을 수치시뮬레이션하여 면밀히 분석하고, 기존의 잠제(submerged breakwater)에 대한 연구와 비교·검토하였다. 먼저, LCS는 유럽과 일본을 비롯한 해외에서 해빈유실방지대책공법의 하나이며, 잠제의 대안으로 여겨지는 LCS에 관한 많은 연구를 수행하였고, 그의 결과들을 집약하여 설계매뉴얼까지 편찬하였다. 지금까지 LCS에 관한 연구는 2차원적인 파랑전달율과 피복재의 안정중량산정에 치우쳐 있으며, 이들은 주로 실험에 기초하여 검토·논의되었다. 본 연구에서는 투과성의 LCS를 대상으로 2차원수치해석과 3차원수치해석을 수행하였다. 여기서, 수치해석은 olaFlow 모델을 사용하였고, 이는 OpenFOAM®(Open source Field Operation And Manipulation) 모델을 근간으로 개발되었으며, 액체와 기체의 혼상류해석, 난류해석 및 쇄파해석이 가능한 유한체적법의 강비선형해석법으로, 3차원 VARANS(Volu- me-Averaged Reynolds-Averaged Navier-Stokes) 방정식에 기초한다. 수치해석에 앞서 olaFlow 모델의 타당성을 검증하기 위해 2차원불투과성잠제 주변에서 파랑변형, 2차원투과성잠제 주변에서 유속, 3차원투과성직립벽 주변에서 수위 및 파압, 3차원불투과성직립벽 주변에서 수위 및 유속 그리고 불규칙파의 수위변동 및 주파수스펙트럼등에 관해 얻어진 기존의 실험결과와 본 수치해석을 비교·검토하였다. 이를 통해 (1) 2차원저천단구조물 주변에서 규칙파동장의 변동특성, (2) 2차원저천단구조물 주변에서 불규칙파동장의 변동특성, (3) 3차원저천단구조물 주변에서 규칙파동장의 변동특성 그리고 (4) 3차원저천단구조물 주변에서 불규칙파동장의 변동특성의 수치해석을 수행하였다. (1)에서는 배후사빈이 존재하는 경우 입사파고와 LCS의 천단고를 변화시키는 경우 LCS에 의한 전달율, 파의 전파과정, LCS 주변에서 평균파고의 공간분포, 평균유속의 공간분포 및 평균난류운동에너지의 공간분포 등의 변동특성을 면밀히 검토하였다. (2)에서는 (1)과 같은 조건에서 불규칙파동장을 적용하여 추가적으로 구조물 주변에서 파랑스펙트럼의 특징을 확인하였다. (3)과 (4)는 3차원수치파동수조에 (1) 혹은 (2)와 같은 단면을 적용하고 입사파고, 천단고 및 개구폭에 변동을 주어 각각 규칙파동장과 불규칙파동장하 평균파고분포(파고분포)와 파의 전파, 해빈류의 분포 및 평균난류운동에너지의 분포를 선행연구인 잠제의 경우와 면밀히 분석·논의하였다.제 1 장 서론 1.1 연구의 배경 및 목적 1 1.2 연구의 구성 4 Reference 5 제 2 장 수치해석이론 2.1 지배방정식 7 2.2 불규칙파의 조파이론 8 Reference 9 제 3 장 2차원저천단구조물의 주변에서 규칙파동장의 변동특성 3.1 수치해석의 검증 11 3.1.1 2차원불투과성잠제 주변에서 파랑변형 11 3.1.2 2차원투과성잠제 주변에서 유속 13 3.2 계산조건 17 3.3 수치해석결과 18 3.3.1 LCS에 의한 전달율 18 3.3.2 파의 전파과정 19 3.3.3 LCS 주변에서 평균파고의 공간분포 20 3.3.4 평균유속의 공간분포 25 3.3.5 평균난류운동에너지의 공간분포 25 3.4 결언 28 Reference 28 제 4 장 2차원저천단구조물의 주변에서 불규칙파동장의 변동특성 4.1 수치해석의 검증 31 4.1.1 불규칙파의 조파 31 4.2 계산조건 34 4.3 수치해석결과 35 4.3.1 LCS 주변에서 파랑스펙트럼 35 4.3.2 LCS에 의한 전달율 38 4.3.3 파의 전파과정 39 4.3.4 LCS 주변에서 파고의 공간분포 40 4.3.5 평균유속의 공간분포 45 4.3.6 평균난류운동에너지의 공간분포 45 4.4 결언 48 Reference 49 제 5 장 3차원저천단구조물 주변에서 규칙파동장의 변동특성 5.1 수치해석의 검증 51 5.1.1 3차원투과성직립벽 주변에서 수위 및 파압 51 5.1.2 3차원불투과성직립벽 주변에서 수위 및 유속 55 5.2 계산조건 56 5.3 수치해석결과 59 5.3.1 정상상태의 판단 59 5.3.2 평균파고분포와 파의 전파 61 5.3.3 해빈류의 분포 66 5.3.4 평균난류운동에너지의 분포 67 5.4 결언 72 Reference 73 제 6 장 3차원저천단구조물 주변에서 불규칙파동장의 변동특성 6.1 계산조건 75 6.2 수치해석결과 76 6.2.1 파고분포와 파의 전파 76 6.2.2 해빈류의 분포 79 6.2.3 평균난류운동에너지의 분포 83 6.3 결언 88 Reference 89 제 7 장 결론 7.1 제 3장에서 결언 91 7.2 제 4장에서 결언 91 7.3 제 5장에서 결언 92 7.4 제 6장에서 결언 93 Reference 94Maste

Cementation of Indirect Restoration

Indirect restoration is commonly used in dental treatment and cementation of the restoration is one of the most important part in that procedure. Understanding the property of dental material in cementation and using it properly at each stage are the key factor to successful treatment. In this article, we studied about different type of adhesive, cement based on the established articles. In addition, we arranged about the considering factors in cementation procedure according to different restoration type.ope

아핀 다양체의 선형 홀로노미

Thesis (master`s)--서울대학교 대학원 :수학과,1995.Maste

受給人의 瑕疵擔保 責任에 관한 硏究

학위논문(박사)--서울대학교 대학원 :법학과 민사법전공,2001.Docto

MOCVD에 의한 GaN stripe 위의 GaN 나노로드의 선택적 성장에 관한 연구

Selective area growth of GaN nanostructures by metal organic vapor phase epitaxy(MOVPE) has attracted great interest due to its novel applications in optoelectronic and photonics. GaN nanorods were grown on the apex of GaN stripes by three dimensional selective growth method. SiO2 mask was partially removed only on the apex area of the GaN stripes by an optimized photolithography for the selective growth. Metallic Au was deposited only on the apex of the GaN stripes and a selective growth of GaN nanorods was followed by a metal organic vapor phase epitaxy (MOVPE). We confirmed that the shape and size of the GaN nanorods depend on growth temperature and flow rates of group III precursor. GaN nanorods were grown having a taper shape which have sharp tip and triangle-shaped cross section. From the TEM result, we confirmed that threading dislocations were rarely observed in GaN nanorods because of the very small contact area for the selective growth. Stacking faults which might be originated from a difference of the crystal facet directions between the GaN stripe and the GaN nanorods were observed in the center area of the GaN nanorods. In this work, we introduce a new growth technology of nanorods which can be grown on specific three dimensional positions. This growth technique has great potentials for the upgrade of conventional devices such as field emitters, gas censors, light emitting diodes, optical resonators and three dimensional power transistors. This technique also may propose an opening of new area for the horizontal nanowire devices interconnected between mesas and complex nanowire networks.1.서론 2.이론 3.실험장치 및 성장방법 4.분석 및 고찰 5.결

警察報酬體系의 合理化方案에 관한 硏究

학위논문(석사)--서울大學校 行政大學院 :行政學科 行政學專攻,1996.Maste

IT system roadmapping method for general contractors

Thesis(masters) --서울대학교 대학원 :건축학과, 2009.2.Maste

Effects of Various Levels of Enzyme and Emulsifier Supplementation on Growth Performance, Pork Quality, Blood Profiles and Economic analysis in Weaning to Finishing Pigs

학위논문 (석사)-- 서울대학교 대학원 : 농업생명과학대학 농생명공학부, 2018. 8. 김유용.This experiment was conducted to evaluate the effect of various levels of enzyme and emulsifier supplementation on growth performance, carcass characteristics and economic analysis in weaning to finishing pigs. A total of 192 weaning pigs ([Yorkshire × Landrace] × Duroc), average 7.26 ± 0.77 kg body weight (BW), were allotted to one of 6 treatments by BW and sex in 4 replications with 8 pigs per pen in 3 × 2 factorial design. Experimental diets were formulated with 0.10% or 0.15% of enzyme along with 0.00%, 0.05% or 0.10% of emulsifier, respectively. In growth performance, G:F ratio was increased with supplementation of emulsifier during late weaning and whole weaning period (P=0.01,0.02) and it was also increased when emulsifier supplementation level was 0.10% (P=0.02) during the whole growing period. The Average daily feed intake (ADFI) was increased during a late growing period (P=0.03) when enzyme supplementation level was 0.15% and that result brought increased Average daily gain (ADG) during early finishing period (P=0.03) when enzyme supplementation level was 0.15%. In blood profiles, BUN, HDL, and LDL did not make significant differences among treatments. In very low-density lipoprotein(VLDL), the result made significant differences among treatments during the late weaning period. Due to emulsifier supplementation decreased, VLDL concentration was changed. In triglyceride (TG), the result also made significant differences during the late weaning period. As supplementation of emulsifier increased, TG in blood was decreased. In glucose, the result was similar to triglyceride and it was also affected by the level of emulsifier in diet during the late weaning period. Free fatty acids in blood were decreased during late weaning period by an effect of supplementation of enzyme and/or emulsifier or synergistic effect of two feed additives. In pork quality, there was no significant difference in carcass trait among treatments except crude ash. The amount of crude ash was increased when the emulsifier supplementation level was 0.05% (P=0.02). The cooking loss was increased as supplementation of enzyme and emulsifier was higher (P<0.01P=0.03, respectively). In economic analysis during the whole experimental period, feed cost was decreased when an enzyme, as well as emulsifier, was provided at 0.1%, respectively, (P<0.05) This result was derived from the improved feed efficiency by supplementation of enzyme and emulsifier. Consequently, supplementation of enzyme 0.10% with emulsifier 0.10% showed a positive effect on growth performance, carcass characteristics and economic analysis of weaning to finishing pigs.Ⅰ. Introduction 1 Ⅱ. Review of Literature 3 1. Introduction 3 1.1 Global market and feed ingredients 3 1.2 Environmental concern with livestock industry in Korea 5 2. The Objectives of Using Enzymes in Animal Feed 7 2.1 Different types of the enzyme in animal feed market 7 2.1.1 Fiber-degrading enzyme 8 2.1.2 Protein-degrading enzyme 8 2.1.3 Starch-degrading enzyme 9 2.1.4 Phytic acid-degrading enzyme 9 3. Enzyme Supplementation to Swine Diets 10 3.1 Digestibility 10 3.2 Growth performance 10 4. Fat digestion in Pigs 11 4.1 Digestive Physiology and digestion of fat in Pigs 11 4.2 Dietary Fat in pigs 14 4.2.1 Fat 14 4.2.2 Dietary Fat Levels and Sources in Pigs 15 4.2.3 Positive effects in the utilization of fat 17 4.2.3.1 Effects of Fat on Growth Performance in Swine. 17 4.2.3.2 Effects of Fat on Nutrient Digestibility in Swine 18 5. The Objectives of Using Emulsifiers in Animal Feed 19 5.1 Definition of Emulsifier 19 5.2 Effects of Exogenous Emulsifier in Pigs 20 5.2.1 Lecithin 20 5.2.2 Lysolecithin 22 Ⅲ. Effect of Various Levels of Enzyme and Emulsifier Supplementation in Weaning to Growing-finishing Pigs 23 Abstract 23 Introduction 25 Materials and Methods 27 Results and Discussion 30 Conclusion 35 Ⅳ. Literature cited 36 Ⅴ. Summary in Korean 60 Ⅵ. Acknowledgment 62Maste