• Title/Summary/Keyword: 반경험식

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Wall-Droplet Interaction Modeling and Comparative Study on Deformation Models for the Improvement of Icing Analysis Under SLD Conditions (SLD 조건에서 착빙 해석 정확도 개선을 위한 Wall-Droplet Interaction 수치 모델링 및 Deformation 모델 비교 연구)

  • Bae, Jinkyu;Yee, Kwanjung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.48 no.4
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    • pp.255-267
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    • 2020
  • Under SLD conditions, due to the large size of droplets, physical phenomena such as wall-droplet interaction and deformation have a significant effect on the icing process. Accordingly, many studies have been conducted in order to computationally simulate SLD effects. As one of the efforts, post-processing method have been proposed to describe wall-droplet interaction effect, which modified collection efficiency using Wright model. However, since the model doesn't properly consider the wall condition, it still overestimated collection efficiency and impingement limit. To solve this problem, impingement areas were divided into 3 different regions, and the post-processing method was introduced with the new wall-droplet interaction model developed based on Bai and Gosman rebound model. In order to consider the effect of deformation, the most suitable model was selected by comparing the deformation models used in the various icing codes. As a result, the modified post-processing method showed improved accuracy in predicting the impingement limits and collection efficiency by further estimating mass flux loss due to rebound, and it was observed that the result was the closest to the experimental data when the deformation effect was included by using Wiegand model.

Proposal of Mobilized Passive Earth Pressure to Allowable Wall Displacement and Movement Types in Sandy Soil (벽체 허용변위와 양상을 고려한 사질토지반에서 수동측토압 제안)

  • Yoon, Young-Ho;Kim, Tae-Hyung;Kim, Tae-O;Woo, Min-seok
    • Journal of the Korean Geotechnical Society
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    • v.39 no.7
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    • pp.5-15
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    • 2023
  • The evaluation of passive earth pressure plays a crucial role in the design of earth-retaining structures such as retaining walls and temporary earth-retaining walls to withstand horizontal earth pressure. In the earth pressure theory, active and passive earth pressures represent the earth pressures at the limit state, where the wall displacement reaches the maximum allowed displacement. In the design of earth-retaining structures, the passive earth pressure is considered as the resisting force. In this context, the limit displacement at which passive earth pressure occurs is significantly greater than that associated with the active earth pressure. Therefore, it is irrational to apply this displacement directly to the calculation of passive earth pressure. Instead, it is necessary to consider the mobilized passive earth pressure exerted at the allowable horizontal displacement to evaluate the structural stability. This study proposes an allowable wall displacement, denoted as 0.002 H (where H represents the excavation depth), based on a literature review that focuses on sandy soils. To calculate the mobilized passive earth pressure from the wall displacement, a semi-empirical equation is proposed. By analyzing the obtained data on mobilized passive earth pressure, a reduction factor applicable to Rankine's passive earth pressure is proposed for practical application in sandy soils under different wall movement types.