• Journal of Korean Society of Water and Wastewater
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• v.25 no.5
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• pp.751-757
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• 2011

The monitoring technique based on electrical conductivity (EC) can provide researchers with some advantages in maintenance management and is cost-effective as compared with existing CSOs monitoring. In this study, the flow rate estimation using EC data was executed in two sites where storm overflow chamber had installed. In the result of A-site, R2 of second order multinomial between dilution ratio of EC and observed flow rate was showed the range of 0.68 ~ 0.77. And $R^{2}$ of B-site was 0.62 ~ 0.81. On the other hand, cumulative frequency of A-site was 43.4 ~ 52.2% in the relative error level of under 20%. And B-site was 10.1 ~ 46.5%. The flow rate estimation formula was improved through consideration of some parameters including antecedent dry days and rainfall duration. And difference between estimated flow rate and observed flow rate in total rainfall event was very small.

• Journal of Drive and Control
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• v.20 no.4
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• pp.123-132
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• 2023

In disaster situations, to facilitate rapid drainage, electric underwater pumps are installed manually. This poses a high risk of electric shock accidents due to a short circuit, and a lot of time is required for hose connection and installation of electrical devices. To solve these problems, a Venturi pump using the venturi effect without external power is used. However, Venturi pumps that operate without external power make it difficult to install flow sensors such as electric devices; consequently, it is difficult to check the real-time flow rate. This paper proposes a flow estimation logic to replace the function of the flow sensor for the venturi pump . To develop the flow estimation logic, the flow characteristics of the venturi pump, according to the operating conditions, were checked. After that, the relationship with the flow rate of the venturi pump was defined using a pressure sensor corresponding to a low-cost sensor. Finally, an analysis of the estimation error was performed using the developed flow estimation logic.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.19 no.2
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• pp.155-162
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• 2023

In nuclear power plants, the flow rate information is a major indicator of the performance of rotating equipment such as pumps, and is a very important one required for facility operation and maintenance. To measure a flow rate, various types of methods have been developed and used. Among them, the differential pressure type using orifice and the direct doppler type using ultrasonic waves are the most commonly used. However, these flow rate measurement methods have limitations in installation, conditions and status of the measuring part, etc. To solve this problem, we have studied a new technique for measuring flow rate from scratch. In this paper, we have devised a technique to estimate the flow rate using an average moving velocity of large-scale eddy in turbulence that occurs in the piping flow field. The velocity of the large-scale eddy can be measured using the pressure fluctuation signals on the inner surface of the pipe. To estimate the flow rate, at first a cross-correlation function is applied to the two pressure fluctuation signals located at different positions in the down stream for calculating the time delay between the moving eddies. In order to validate the proposed flow rate estimation method, CFD analyses for the internal turbulence flow in pipe are conducted with a fixed flow condition, where the pressure fluctuation signals on the pipe inner surface are simulated. And then the average flow velocity of the large scale eddy is to be estimated. The estimated flow velocity is turned out to be similar to the fixed (known) flow rate.

• Korean Journal of Agricultural Science
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• v.47 no.1
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• pp.19-28
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• 2020

This study proposed a simple estimation method for irrigation return flow from paddy fields using the water balance model. The merit of this method is applicability to other paddy fields irrigated from agricultural reservoirs due to the simplicity compared with the previous monitoring based estimation method. It was assumed that the unused amount of irrigation water was the return flow which included the quick and delayed return flows. The amount of irrigation supply from a reservoir was estimated from the reservoir water balance with the storage rate and runoff model. It was also assumed that the infiltration was the main source of the delayed return flow and that the other delayed return flow was neglected. In this study, the amount of reservoir inflow and water demand from paddy field are calculated on a daily basis, and irrigation supply was calculated on 10-day basis, taking into account the uncertainty of the model and the reliability of the data. The regression rate was calculated on a yearly basis, and yearly data was computed by accumulating daily and 10-day data, considering that the recirculating water circulation cycle was relatively long. The proposed method was applied to the paddy blocks of the Jamhong and Seosan agricultural reservoirs and the results were acceptable.

• Nuclear Engineering and Technology
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• v.48 no.5
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• pp.1264-1272
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• 2016

The accurate estimation of leak rate through cracks is crucial in applying the leak before break (LBB) concept to pipeline design in nuclear power plants. Because of its importance, several programs were developed based on the several proposed flow models, and used in nuclear power industries. As the flow models were developed for a homogeneous pipe material, however, some difficulties were encountered in estimating leak rates for bimaterial pipes. In this paper, a flow model is proposed to estimate leak rate in bimaterial pipes based on the modified Henry-Fauske flow model. In the new flow model, different crack morphology parameters can be considered in two parts of a flow path. In addition, based on the proposed flow model, a program was developed to estimate leak rate for a crack with linearly varying cross-sectional area. Using the program, leak rates were calculated for through-thickness cracks with constant or linearly varying cross-sectional areas in a bimaterial pipe. The leak rate results were then compared and discussed in comparison with the results for a homogeneous pipe. The effects of the crack morphology parameters and the variation in cross-sectional area on the leak rate were examined and discussed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.4
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• pp.342-351
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• 2010

UAV (Unmanned Aerial Vehicle) have an INS(Inertial Navigation System) equipment and also have an electro-optical Equipment for mission. This paper proposes the vision based attitude estimation algorithm using Kalman Filter and Optical flow for UAV. Optical flow is acquired from the movie of camera which is equipped on UAV and UAV's attitude is measured from optical flow. In this paper, Kalman Filter has been used for the settlement of the low reliability and estimation of UAV's attitude. Algorithm verification was performed through experiments. The experiment has been used rate table and real flight video. Then, this paper shows the verification result of UAV's attitude estimation algorithm. When the rate table was tested, the error was in 2 degree and the tendency was similar with AHRS measurement states. However, on the experiment of real flight movie, maximum yaw error was 21 degree and Maximum pitch error was 7.8 degree.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.3
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• pp.14-20
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• 2018

An estimation law of air mass flow rate for high speed engine control is presented. The variables of mass estimation equations are modified to measurable variables which can be obtained during flight, and the effectiveness of each variable to the estimation accuracy is evaluated. The equation is modified to a simplified form, and the uncertainty is evaluated. In addition, reference data for the selection of estimation methods is suggested by considering the sensitivity analysis of sensor error.

• Nuclear Engineering and Technology
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• v.47 no.3
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• pp.332-339
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• 2015

The leak before break (LBB) concept is widely used in designing pipe lines in nuclear power plants. According to the concept, the amount of leaking liquid from a pipe should be more than the minimum detectable leak rate of a leak detection system before catastrophic failure occurs. Therefore, accurate estimation of the leak rate is important to evaluate the validity of the LBB concept in pipe line design. In this paper, a program was developed to estimate the leak rate through circumferential cracks in pipes in nuclear power plants using the Henry-Fauske flow model and modified Henry-Fauske flow model. By using the developed program, the leak rate was calculated for a circumferential crack in a sample pipe, and the effect of the flow model on the leak rate was examined. Treating the crack morphology parameters as random variables, the statistical behavior of the leak rate was also examined. As a result, it was found that the crack morphology parameters have a strong effect on the leak rate and the statistical behavior of the leak rate can be simulated using normally distributed crack morphology parameters.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.6
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• pp.1-12
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• 1997

In an SI engine, the characteristics of the air flow is important not only for the design of the intake system geometry but also for the accurate measurement of the induction air mass. In this study, an air flow rate measurement using the ultrasonic flow meter and hot wire flow meter was conducted at the upstream of the intake port and the throttle. At the upstream of the intake port, the pulsating flow into the cylinder affected by the pressure wave was detected directly with the flow meters instead of pressure sensors. At the upstream of the throttle, the reverse flow phenomena were showed by comparing the flow pattern measured by the hot wire air flow meter and the ultrasonic air flow meter. The results of this study can be used for the analysis of the tuning effect in the intake manifold and estimation of the error in real time measurement for the air flow rate.

• Journal of Korean Society of Transportation
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• v.13 no.1
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• pp.167-183
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• 1995

The objective of study is to evaluate highway capaicty estimation alternative and to develop capacity from statistical distribution of observed traffic flow. Speed-Volume relation is analyzed from vehicle's headway distribution eliminating the long headway by confidence intervals 99%, 95%, 90%. Capacity estimate alternatives were evaluated from 95% , 90%, 85% level of cummulative distribution of observed hourly traffic flow adjusted to confidence intervals. The result of investigation revealed that maximum hourly rate of flow is 2, 130pcu at confidence interval of 995, 2, 233pcu at 95%, 2, 315pcu at 90% respectively. Compared to the capacity of 2, 200pcu per hour per lane used in HCM and KHCM(Korea Highway Capacity Manual), capa챠y appears to correspond to confidence interval of 95%. Using the traffic flow rate at confidence interval of 95% the maximum hourly flow rate is 2, 187pcu at 95% of cummulative volume distribution, 2, 153pcu at 90%, 2, 215pcu at 85%. The study suggests that raional capacity esimation alternative is to take the 95% of cummulative distribution of observed hourly traffic flow at 95% confidence headway interval eliminating 5% long headway.(i.e. 95-95 rule)