• Title, Summary, Keyword: Radius influence

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The Effect of Atmospheric Flow Field According to the Radius Influence and Nudging Coefficient of the Objective Analysis on Complex Area (자료동화의 영향반경과 동화강도가 복잡지형 기상장 수치모의에 미치는 영향)

  • Choi, Hyun-Jung;Lee, Hwa-Woon;Sung, Kyoung-Hee;Kim, Min-Jung
    • Journal of Environmental Science International
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    • v.18 no.3
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    • pp.271-281
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    • 2009
  • In order to reduce the uncertainties and improve the air flow field, objective analysis using observational data is chosen as a method that enhances the reality of meteorology. To improve the meteorological components, the radius influence and nudging coefficient of the objective analysis should perform a adequate value on complex area for the objective analysis technique which related to data reliability and error suppression. Several numerical experiments have been undertaken in order to clarify the impacts of the radius influence and nudging coefficient of the objective analysis on meteorological environments. By analyzing practical urban ground conditions, we revealed that there were large differences in the meteorological differences in each case. In order to understand the quantitative impact of each run, the Statistical analysis by estimated by MM5 revealed the differences by the synoptic conditions. The strengthening of the synoptic wind condition tends to be well estimated when using quite a wide radius influence and a small nudging coefficient. On the other hand, the weakening of the synoptic wind is opposite.

Permeability-increasing effects of hydraulic flushing based on flow-solid coupling

  • Zhang, Jiao;Wang, Xiaodong
    • Geomechanics and Engineering
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    • v.13 no.2
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    • pp.285-300
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    • 2017
  • Shallow coal resources are increasingly depleted, the mining has entered the deep stage. Due to "High stress, high gas, strong adsorption and low permeability" of coal seam, the gas drainage has become more difficult and the probability of coal and gas outburst accident increases. Based on the flow solid coupling theory of coal seam gas, the coupling model about stress and gas seepage of coal seam was set up by solid module and Darcy module in Comsol Multiphysics. The gas extraction effects were researched after applying hydraulic technology to increase permeability. The results showed that the effective influence radius increases with the expanded borehole radius and drainage time, decreases with initial gas pressure. The relationship between the effective influence radius and various factors presents in the form: $y=a+{\frac{b}{\left(1+{(\frac{x}{x_0})^p}\right)}}$. The effective influence radius with multiple boreholes is obviously larger than that of the single hole. According to the actual coal seam and gas geological conditions, appropriate layout way was selected to achieve the best effect. The field application results are consistent with the simulation results. It is found that the horizontal stress plays a very important role in coal seam drainage effect. The stress distribution change around the drilling hole will lead to the changes in porosity of coal seam, further resulting in permeability evolution and finally gas pressure distribution varies.

The influence of punch and die shape radius in non-axisymmetric deep drawing products (비축대칭 디프 드로잉 제품에서 펀치 및 다이형상반경의 영향)

  • 박동환
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.22-25
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    • 1999
  • 'There are a lot of process variables, exerted influence on the formability of products, in deep drawing process. Particularly, it is important that the punch and die shape radius of the process variables. Though researches have been performed on the deep drawing of sheet metal forming, like this study, but it is insufficient the actual circumstances that researches for process variables of the non-axisymmetric deep drawing products. In this study, An effect on thickness distribution is grasped as alteration of the punch and die shape radius in the process of non-axisyrnmetric deep drawing products, and then the optimal punch and die shape radius were presented, they were verified by the numerical analysis method (FEM).

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The Influence of Gap Length and Tip Radius on Breakdown of Electrical Insulating Oil (전기절연유의 절연파괴에 미치는 전극간격 및 곡률반경의 영향)

  • Kang, Seong-Hwa;Chae, Hong-In;Lee, Jong-Pil;Lim, Kee-Joe
    • Journal of the Korean Society of Safety
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    • v.19 no.1
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    • pp.56-59
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    • 2004
  • In this paper, we investigated the influence of gap length and tip radius on breakdown of mineral based insulation oil. Applied voltages were DC and AC voltage. Electrode system was needle-plane structure. The tip radius of needle electrode was 5, 10, 20 and 25${\mu}m$, respectively. We measured breakdown voltage for each of tip radius with increasing electrode gap, 2mm to 12mm. Electric breakdown strength at tip was calculated using Mason's equation contained geometric figure. As gap length increased, breakdown strength increased linearly. But, as tip radius of needle increased, breakdown strength decreased exponentially. It can be explained by the phenomenon that electron is easily injected, as tip radius increases, and effective work function decreases. When appling DC voltage, breakdown strength was higher when polarity of needle was negative than positive. It is because of the space charge effect in accordance with the influence of liquid motion.

Groundwater Flow Analysis using Numerical model in Small Basin (소규모유역의 수치모헝을 이응한 지하수 유동해석)

  • 최윤영
    • Journal of Environmental Science International
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    • v.12 no.6
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    • pp.615-626
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    • 2003
  • The applied model for this study area is WINFLOW using mite element method, It is thought that the simulation result by WINFLOW model under the steady flow state reflects well the ground water distribution within the reliability level which shows the error range of 1.1% to 8.0% from the comparison between the computed values and the observed, and analyzed that the constant head distribution is shown along the east-west direction and gentle and stable head gradient along the north-south direction. Ground water of the study area shows stable movement from the south to the stream area, and the particle trace for each location shows relatively linear shape from the upstream to the pumping location while the radius of influence according to the pumping amount shows a significant difference at the down stream area from the pumping location. The simultaneous pumping from P and P1 shows more complicated appearance, not the increase of the radius of influence than pumping from a single well P or P1, and it is analyzed that the particle path takes nearly linear form. It is known that the flow direction of the ground water and the velocity of the flow affect on the magnitude of the radius of influence of the wells from the fact that the more decreasing pattern of the ground water head is observed at the side of the well and the down stream area than the upstream area when the ground water moves from south to north regarding the radius of influence according to the pumping amount. Satisfactory results in analyses of ground water movement are obtained through the significant reduction of the physical uncertainties in the flow system as well as the relatively convenient model application using WINFLOW model which is proposed in this study.

Analyses of Stress Intensity Factors for Slant Crack Emanation from Circular Inclusion by Boundary Element Method (경계요소법에 의한 원형함유물에서 파생되는 경사균열의 응력확대계수 해석)

  • Park, Sung-Oan;Hwang, Soon-Won
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.7 no.5
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    • pp.72-84
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    • 1998
  • In order ot study the influence of a circular inclusion on a stress field near a crack tip, mutual interference of a slant crack and the circular inclusion is analyzed of a bimaterial inclusion. As the crack emanates at the equivalent slant crack angle the correction factors FⅠ and FⅡ for the inclusion wit small Young's modulus were found to decrease as the inclusion radius increased. The correction factors for inclusion with large Young's modulus increase as the inclusion radius increases at the equivalent radius of the inclusion, the correction factors decrease as the slant crack angle increases for the aspect ratio $\frac{c}{W}$ = 0.1 irrespective of the Young's modulus. For $\frac{c}{W}$ greater than 0.2, they increase as the slant crack angle increases. There is no influence of stress mutual interfce after crack emanates beyond the inclusion radius.

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Investigation of the Assimilated Surface Wind Characteristics for the Evaluation of Wind Resources (풍력자원 평가를 위한 바람자료 동화 특성 평가)

  • Lee, Hwa-Woon;Kim, Min-Jung;Kim, Dong-Hyeuk;Kim, Hyun-Goo;Lee, Soon-Hwan
    • Journal of Korean Society for Atmospheric Environment
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    • v.25 no.1
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    • pp.1-14
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    • 2009
  • Wind energy has been recognized as one of the most important and fastest growing energy resources without emission of air pollutant. Thus, it is necessary to predict wind speed and direction accurately both in time and space toward the efficient usage of wind energy. Numerical simulation experiments using the Fifth-Generation Mesoscale Model (MM5) are carried out to clarify the impact of surface observation data assimilation on the estimation of wind energy resources. The EXP_Radius run was designed with respect to the radius of influence in the Four-Dimensional Data Assimilation (FDDA), and the EXP_Impact run was made by changing the nudging coefficient that determines the relative magnitude of the nudging term. The simulation period covers a clear-sky event on 3 - 5 June 2007 and another is on 2 - 4 December 2006. It is found that the simulated results are very sensitive to the radius of influence and nudging parameters in the FDDA. The further analysis of the results shows that the impact of the radius of influence tends to be stronger in weak synoptic flow episode than that in strong synoptic flows episode. The nudging factor is also sensitive to the intensity of the synoptic flows.

The Effect of Reciprocating Motion on Heat Transfer in the Roughened Rectangular Channel (거친사각채널에서 왕복운동이 열전달에 미치는 효과)

  • 안수환;손강필
    • Journal of Advanced Marine Engineering and Technology
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    • v.26 no.6
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    • pp.646-652
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    • 2002
  • The influence of reciprocating frequency and radius on heat transfer in the roughened rectangular channel is experimentally investigated. The aspect ratio (width/height) of the duct is 2.33 and the rib height is one fifteenth of the duct height. And the ratio of rib-to-rib distance to rib height is 10. The discrete ribs were periodically attached to the button wall of the duct with a parallel orientation. The parametric test matrix involves Reynolds number, reciprocating, and reciprocating radius, in the ranges, 1,000∼6,000, 1.7∼2.5 HB and 7∼15cm, respectively. The combined effects of reciprocating frequency and reciprocating radius have considerable influence on the heat transfer due to the modified vortex flow structure.

Parameters influencing seismic response of horizontally curved, steel, I-girder bridges

  • Linzell, Daniel G.;Nadakuditi, Venkata P.
    • Steel and Composite Structures
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    • v.11 no.1
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    • pp.21-38
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    • 2011
  • This study examines the influence of curved, steel, I-girder bridge configuration on girder end reactions and cross frame member forces during seismic events. Simply-supported bridge finite element models were created and examined under seismic events mimicking what could be experienced in AASHTO Seismic Zone 2. Bridges were analyzed using practical ranges of: radius of curvature; girder and cross frame spacings; and lateral bracing configuration. Results from the study indicated that: (1) radius of curvature had the greatest influence on seismic response; (2) interior (lowest radius) girder reactions were heavily influenced by parameter variations and, in certain instances, uplift at their bearings could be a concern; (3) vertical excitation more heavily influenced bearing and cross frame seismic response; and (4) lateral bracing helped reduce seismic effects but using bracing along the entire span did not provide additional benefit over placing bracing only in bays adjacent to the supports.