• 한국유체기계학회 논문집
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• 제9권4호
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• pp.7-12
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• 2006

Flow meters in partly filled pipes are set up and run in Korea nowadays, but there are no standard calibration procedures for the flow meters in accordance with ' ISO/IEC 17025. The standard calibration procedure based on the standard calibration procedures for flow meter in closed conduits and the technical notes of flow meter's makers ' is developed. The measurement uncertainty of the calibration for the flow meter in partly filled pipes is evaluated.

• 한국가시화정보학회지
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• 제16권2호
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• pp.23-30
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• 2018

The present study compares flow fields reconstructed by data assimilation method with different combinations of parameters. As a data assimilation method, Vortex-in-Cell-sharp (VIC#), which supplements additional constraints and multigrid approximation to Vortex-in-Cell-plus (VIC+), is used to reconstruct flow fields from scattered particle tracks. Two parameters, standard deviation of Gaussian radial basis function (RBF) and grid spacing, are mainly tested using artificial data sets which contain few particle tracks. Consequent flow fields are analyzed in terms of flow structure sizes. It is demonstrated that sizes of the flow structures are proportional to an actual scale of the standard deviation of RBF. It implies that a combination of larger grid spacing and smaller standard deviation which preserves the actual standard deviation is able to save computational resources in case of a low track density. In addition, a simple comparison using an experimental data filled with dense particle tracks is conducted.

• Advances in concrete construction
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• 제10권5호
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• pp.381-391
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• 2020

This study aimed to develop reference materials (RMs) for mortar that can simulate the initial flow characteristics with constant quality over a long period. Through the previous research on the development of RMs for cement paste, the combination of limestone, glycerol, and water was used as the basic matrix for developing RMs for mortar in this study. In addition, glass beads of three particle sizes (0.5, 1.0, and 2.0 mm) and ISO standard sand were selected as tentative candidates to derive fine aggregate substitutes. The mixture of glass beads could simulate the initial flow characteristics of mortar, but under the same mixing ratio, replicates showed an unstable tendency to indicate inconsistent values due to the generation of electrostatic properties between materials and equipment. On the other hand, the mixture using ISO standard Sand not only simulates the constant flow characteristics for a long period of time, but also shows stable results with little error in replicates. Therefore, limestone, glycerol, ISO standard sand, and water were finally determined as components that met the required properties of RMs for mortar. The effect of each component on the flow characteristics of RMs was analyzed. It was found that glycerol increased the cohesion between the particles of standard sand, resulting in a constant increase both in the plastic viscosity and yield stress. Both limestone and standard sand had a dominant effect on the yield stress. The relationships between various mortar mixing ratios and the corresponding mixing ratios of RMs were established. In addition, the results of the verification experiment showed that the rheological properties of the RMs obtained through the relationships correlated with various water/cement ratios and the fine aggregate volume fractions of mortar obtained with same manner. In other words, the RMs for mortar developed in this study can be used as standard samples because they can simulate the initial flow characteristics of mortar of various mixing ratios for a long period without any chemical changes.

• 대한기계학회논문집B
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• 제30권12호
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• pp.1139-1146
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• 2006

Light Oil Flow Standard System(LOFSS) in Korea Research Institute of Standards and Science(KRISS) was designed for oil flowmeter calibration. In order to extend the flow range from 120 $m^3/h$ to 200 $m^3/h$, the build-up technique was applied with two positive displacement flowmeters as master flowmeter. The master flowmeters were calibrated against with LOFSS, which has 0.04 % uncertainty of flow quantity determination, then the test flowmeter is calibrated against two master flowmeters. For uncertainty analysis, the repeatability of master flowmeters, the variation of the fluid density and the pipe volume due to temperature change were scrutinized. The contribution of each uncertainty factors to the calibrator and the correlation of each factors were discussed. For investigating the feasibility of uncertainty analysis, a turbine flowmeter as a transfer package was tested with LOFSS and two reference flowmeter. The hypothesis test for both results was coincide with a 95 % significant level. This means that the uncertainty analysis procedure of the calibrator is reasonable and the extension of flow range with master meters was carry out successfully.

• 환경영향평가
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• 제21권1호
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• pp.161-169
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• 2012

Recently various attempts have been made to apply HSPF model to calculate runoff and diffuse pollution loads of stream and reservoir watersheds. Because the role of standard flow is very important in the water quality modelling of Total Water Pollution Load Management, HSPF was used as a means of estimating standard flow. In this study, BASINS 4.0 and WinHSPF was applied to the Gomakwoncheon watershed, genetic algorithm(GA) and influence coefficient algorithm were used to calibrate the runoff parameters of the WinHSPF. The objective function is the sum of the squares of the normalized residuals of the observed and calculated flow and it is optimized using GA. Estimates of the optimum runoff parameters are made at each iteration of the influence coefficient algorithm. The calibration results showed a relatively good correspondence between the observed and the calculated values. The standard flow(Q275) of the Gomakwoncheon watershed was estimated using the ten years of weather data.

• 한국수소및신에너지학회논문집
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• 제33권6호
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• pp.684-691
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• 2022

Hydrogen fuel cell electric vehicles are typically refueled at a wide range of temperatures (-40℃ to 85℃) in the hydrogen refueling station in accordance with the worldwide accepted standard. Currently, there is no traceable method by which to verify and calibrate the hydrogen flowmeters to be used at hydrogen refueling stations except for a water calibration process as a conventional method. KRISS hydrogen field test standard based on the gravimetric principle was developed to verify the measurement accuracy of the mass flowmeter to be used at hydrogen refueling stations for the first time in Korea.

• 대한기계학회논문집B
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• 제20권10호
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• pp.3272-3281
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• 1996

The flow analysis method which had been developed for the numerical calculation of 3-dimensional, incompressible and turbulent flow within an axial compressor was extended to the flow field within centrifugal impeller. In this method based on the SIMPLE(Semi Implicit Method Pressure Linked Equations) algorithm, the coordinate transformation was adopted and the standard k-.epsilon. model using wall function was used for turbulent flow analysis. The calculated flow fields have agreed very well with measurement results. Especially, 3-dimensional and viscous flow characteristics including secondary flows, jet-wake flow and decreased pressure rise along impeller passage, which can't be predicted by inviscid Q3D calculation were predicted very reasonably.

• 한국가시화정보학회지
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• 제19권2호
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• pp.63-73
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• 2021

It is essential to accurately predict the change in water level, velocity, and flow rate for each passage of the grit chamber according to the operating conditions of the pump. In this study, VOF multiphase flow analysis was performed, and the flow characteristics of the grit chamber were predicted. As a result of simulations, the sedimentation phenomenon after the entrance of the grit chamber channel is expected to occur on the side walls. When 6 channels are used, the average speed of the channels is about 52% of the design standard, and when 4 channels are used, the value increases to 74% of the design standard. The average water level in the channels tends to decrease as the flow velocity increases, and the water level in the absorption well with a larger flow rate is maintained lower than that in the absorption well with a smaller flow rate.

• 폴리머
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• 제25권6호
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• pp.855-865
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• 2001

MOLDFLOW사의 CAE S/W를 사용하여 A사의 TV speaker grille의 최적 성형 조건을 도출하였는데 캐비티 안으로 충전되는 수지의 양을 조절하는 방법 중 flow balance, runner balance, 그리고 이 두 가지를 절충한 세 가지 방법으로 유동과 보압 해석을 수행하였다. 또한 실제로 각각의 온도별 점도와 전단속도를 측정한 결과(local database)를 이용하여 해석하고, standard database에 의한 해석결과와 비교 검토하였다. Speaker grille에서 flow balance는 성형품의 weld line을 최소화함으로써 양호한 외관과 weld line의 기계적 물성 저하를 최소화시켰으나, 제품 중앙부의 과충전으로 인한 과도한 변형이나 gas가 발생하는 단점이 나타났다. Runner balance는 각 gate로부터 사출되는 수지의 양을 균등하게 조절함으로써 flow balance의 단점을 보완하였으나, weld line의 외관과 기계적 물성이 저하하는 단점이 나타났다. 그러나 flow balance와 runner balance를 절충한 형태의 runner의 직경을 변형함으로써 두 방법이 가지는 단점을 보완하였다. 또한 각각의 온도에 대한 점도와 전단속도를 실측한 local database와 기존의 standard database에 의한 해석 결과를 비교한 결과, 실측의 점도가 다소 높게 측정되고 온도 분포의 편차가 넓게 나타났음에도 불국하고 두 data의 해석 결과는 거의 차이가 없음이 확인되었다.

• 대한의용생체공학회:의공학회지
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• 제36권4호
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• pp.115-122
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• 2015

A standard air flow generator system was developed to generate air flows of various levels simultaneously applied to two different air flow transducer modules. Axes of two identical standard syringes for spirometer calibration were connected with each other and driven by a servo-motor. Linear displacement transducer was also connected to the syringe axis to accurately acquire the volume change signal. The user can select either sinusoidal or square waveform of volume change and manually input any volume as well as maximal flow rate levels ranging 0~3 l and 0~15 l/s, respectively. Various volume and flow levels were input to operate the system, then the volume signal was acquired followed by numerical differentiation to obtain the air flow signal. The measured volumes and maximal air flow rates were compared with the user input data. The relative errors between the user-input and the measured stroke volumes were all within 0.5%, demonstrating very accurate driving of the system. In case of the maximal flow rate, relatively large error was observed when the syringe was driven very fast within a very short time duration. However, except for these few data, most measured flow rates revealed relative errors of approximately 2%. When the measure and user-input stroke volume and maximal flow rate data were analyzed by linear regression analysis, respectively, the correlation coefficients were satisfactorily higher than 0.99 (p < 0.0001). These results demonstrate that the servo-motor controls the syringes with enough accuracy to generate standard air flows. Therefore, the present system would be very much practical for calibration process as well as performance evaluation and comparison of two different air flow transducer modules.