• Journal of the Korean Society of Visualization
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• v.17 no.3
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• pp.46-51
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• 2019

Rotor wake interaction must be considered to understand the quadrotor flight, and the rotor separation distance is an important parameter that affects the rotor wake interaction. In this study, the wake characteristics were investigated with varying the rotor separation distance. The velocity field in the rotor wake was measured using digital PIV for hovering mode at Re = 34,000, and the wake boundaries from the inner and outer rotor tips were quantitatively compared with varying the rotor separation distance. The symmetric rotor-tip vortex shedding about the rotor axis was found at a large rotor separation distance. However, the wake boundary became more asymmetric about the rotor axis with decreasing the rotor separation distance. At the minimum rotor separation distance, in particular, a faster vortex decay was observed due to a strong vortex interaction between adjacent rotors.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.5
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• pp.393-400
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• 2002

Separation distance between industrial source and residential areas to avoid odor annoyance was investigated using AUSPLUME model. A Gaussian plume model (AUSPLUME) for the dispersion was used to calculate odor emission from ground level area source. Using the dispersion model to calculate ambient odor concentrations, the separation distance between industrial source and residental areas was defined by %HA (percentage of highly annoyed person) and odor percentile concentration (C98). The result was compared with the separation distance of various nation guidelines for livestock buildings. The calculated separation distance for industrial source showed similar pattern comparing with various guidelines for livestock buildings.

• Journal of Environmental Science International
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• v.28 no.9
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• pp.737-749
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• 2019

In this study, the sensitivity analysis of hydraulic conductivity and separation distance (distance between injection well and pumping well) was analyzed by establishing a conceptual model considering the hydrogeologic characteristics of facility agricultural complex in Korea. In the conceptual model, natural characteristics (topography and geology, precipitation, hydraulic conductivity, etc.) and artificial characteristics (separation distance from injection well to pumping well, injection rate and pumping rate, etc.) is entered, and sensitivity analysis was performed 12 scenarios using a combination of hydraulic conductivity ($10^{-1}cm/sec$, $10^{-2}cm/sec$, $10^{-3}cm/sec$, $10^{-4}cm/sec$) and separation distance (10 m, 50 m, 100 m). Groundwater drawdown at the monitoring well was increased as the hydraulic conductivity decreased and the separation distance increased. From the regression analysis of groundwater drawdown as a hydraulic conductivity at the same separation distance, it was found that the groundwater level fluctuation of artificial recharge aquifer was dominantly influenced by hydraulic conductivity. In the condition that the hydraulic conductivity of artificial recharge aquifer was $10^{-2}cm/sec$ or more, the radius of influence of groundwater level was within 20 m, but In the condition that the hydraulic conductivity is $10^{-3}cm/sec$ or less, it is confirmed that the radius of influence of groundwater increases sharply as the separation distance increases.

• Earthquakes and Structures
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• v.22 no.2
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• pp.147-155
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• 2022

Regarding the importance of seismic pounding, the available standards and guidelines specify minimum separation distance between adjacent buildings. However, the rules in this field are generally based on some simple assumptions, and the level of confidence is uncertain. This is attributed to the fact that the relative response of adjacent structures is strongly dependent on the frequency content of the applied records and the Eigen frequencies of the adjacent structures as well. Therefore, this research aims at investigating the separation distance of the buildings through a probabilistic-based algorithm. In order to empower the algorithm, the record-to-record uncertainties, are considered by probabilistic approaches; besides, a wide extent of material nonlinear behaviors can be introduced into the structural model by the implementation of the hysteresis Bouc-Wen model. The algorithm is then simplified by the application of the linearization concept and using the response acceleration spectrum. By implementing the proposed algorithm, the separation distance in a specific probability level can be evaluated without the essential need of performing time-consuming dynamic analyses. Accuracy of the proposed method is evaluated using nonlinear dynamic analyses of adjacent structures.

• Earthquakes and Structures
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• v.18 no.5
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• pp.543-553
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• 2020

Past earthquakes experience shows that serious damage or collapse of buildings have dramatically accrued when sufficient separation distance has not been provided between two adjacent structures. The majority of past studies related to the pounding topic indicate that obtaining the gap size between two buildings is able to prevent collision and impact hazards during seismic excitations. Considering minimization of building collisions, some relationships have been suggested to determine the separation distance between adjacent buildings. Commonly, peak lateral displacement, fundamental period and natural damping as well as structural height of two adjacent buildings are numerically considered to determine the critical distance. Hence, the aim of present study is to focus on all mentioned parameters and also utilizing the main characteristic of earthquake record i.e. PGA to examine the lateral displacement of irregular structures close to each other and also estimate the sufficient separation distance between them. Increasing and decreasing the separation distance is inherently caused economical problems due to the land ownership from a legal perspective and pounding hazard as well. Therefore, a new equation is proposed to determine the optimum critical distance. The accuracy of the proposed formula is validated by different models and various earthquake records.

• Structural Engineering and Mechanics
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• v.67 no.5
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• pp.427-437
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• 2018

Structural pounding is commonly observed phenomenon during major ground motion, which can cause both structural and architectural damages. To reduce the amount of damage from pounding, the best and effective way is to increase the separation distance. Generally, existing design procedures for determining the separation distance between adjacent buildings subjected to structural pounding are based on approximations of the buildings' peak relative displacement. These procedures are based on unknown safety levels. The aim of this research is to estimate probabilistic separation distance between adjacent structures by considering the variability in the system and uncertainties in the earthquakes characteristics through comprehensive numerical simulations. A large number of models were generated using a robust Monte-Carlo simulation. In total, 6.54 million time-history analyses were performed over the adopted models using an ensemble of 25 ground motions as seismic input within OpenSees software. The results show that a gap size of 50%, 70% and 100% of the considered design code for the structural periods in the range of 0.1-0.5 s, leads to have the probability of pounding about 41.5%, 18% and 5.8%, respectively. Finally, based on the results, two equations are developed for probabilistic determination of needed structural separation distance.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.215-218
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• 2007

In this paper, we have analyzed the effects from the change of separation distance between grounding equipment at end of telecommunication line and the inducting facilities in power inducting situation. In the result of measurement, we can see that as the separation distance between grounding equipment ant end of telecommunication line and the inducting facility become longer, the induced noise level and PIF level is decreased. From the another experiment results about the effect of changing the impedance size in both ends of telecommunication line, however, we already knew that as the ground impedance at either end of the telecommunication line become grower, the noise level is increased, and as the ground impedance at either end of the telecommunication line become smaller, the noise level is decreased. Hence we can not define the relationship exactly between separation distance from inducting facility to inducted facility and the induced noise level because when the grounding equipment is moved, its impedance size is changed too. In conclusion, changing the separation distance between grounding equipment at end of telecommunication line and the inducting facilities have not influence on the induced noise level.

• Structural Engineering and Mechanics
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• v.78 no.2
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• pp.219-230
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• 2021

International seismic codes stipulate that adjacent buildings should be separated by a specified minimum distance, otherwise the pounding effect should be considered in the design. Recent researches proposed an alternative method (Double Difference Combination Rule) to estimate seismic gap between structures, as this method considers the cross relation of adjacent buildings behavior during earthquakes. Four different criteria were used to calculate the minimum separation distance using this method and results are compared to the international codes for five separation cases. These cases used four case study buildings classified by different heights, lateral load resisting systems and fundamental periods of vibrations to assess the consistency in results for the alternative methods. Non-linear analysis was performed to calculate the inelastic displacements of the four buildings, and the results were used to evaluate the relation between elastic and inelastic displacements due to the ductility of structural elements resisting seismic loads. A verification analysis was conducted to guarantee that the separation distance calculated is sufficient to avoid pounding. Results shows that the use of two out of the four studied methods yields separation distances smaller than that calculated by the code specified equations without under-estimating the minimum separation distance required to avoid pounding.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.145-150
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• 2004

In this study the numerical analysis on staging flow with forward ejector is conducted. The forward ejector plays a vital role in staging, which jets out from aftbody. This staging environment needs careful flow analysis for securing staging safety Present study investigates the steady inviscid staging flow phenomena with variation of separation distance. The performance index is forebody base pressure coefficients. The three dominant flow phenomena are observed according to separation distance which could be told as impinging stage, cavity vortex dominancy stage, and pure base flow characteristics stage. Impinging stage shows high thrust for forebody as one might think. However, important point is that cavity vortex dominancy stage can be more favorable for separation than impinging stage as one simply think in certain separation distance.

• International Journal of Highway Engineering
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• v.19 no.6
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• pp.191-199
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• 2017

PURPOSES : The objective of this study is to develop a methodology to estimate the minimum required separation distance (MRSD) between a vehicle and a bicycle when overtaking. METHODS : Three steps have been conducted to develop a methodology to estimate MSRD. First, a literature review has been conducted on the measurement of MSRD, and how it may be applied in Korea. Second, two assumptions have been made to develop a methodology to estimate the MSRD. The first assumption is that the maximum separation distance between a vehicle and a bicycle can be observed when they are at the same location longitudinally. In addition, it is assumed that the separation distance is invalid when the contra-flow exists. Finally, three cameras were installed at a height of 10 m to record the vehicle-bicycle interaction. Moreover, the vehicle trajectories as well as the separation distance were coded and analyzed. Through the hypothesis test and the interval estimation, the sample mean was tested and the confidence interval was estimated. RESULTS : 141 records of separation distance data were collected, and the hypothesis test demonstrated that the MSRD in Korea is significantly higher than other countries. In addition, the confidence interval of the population mean of MSRD is from 1.51 m to 1.65 m with 95% level of confidence. CONCLUSIONS : It is expected that the proposed methodology to estimate MSRD would be beneficial in studying road safety of vehicles and bicycles. Also, the proposed MSRD is expected to be designated in the act of road and transportation.