Partition method of wall friction and interfacial drag force model for horizontal two-phase flows

Takashi Hibiki,정재준 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.4

The improvement of thermal-hydraulic analysis techniques is essential to ensure the safety and reliability of nuclear power plants. The one-dimensional two-fluid model has been adopted in state-of-theart thermal-hydraulic system codes. Current constitutive equations used in the system codes reach amature level. Some exceptions are the partition method of wall friction in the momentum equation ofthe two-fluid model and the interfacial drag force model for a horizontal two-phase flow. This study isfocused on deriving the partition method of wall friction in the momentum equation of the two-fluidmodel and modeling the interfacial drag force model for a horizontal bubbly flow. The onedimensional momentum equation in the two-fluid model is derived from the local momentum equation. The derived one-dimensional momentum equation demonstrates that total wall friction should beapportioned to gas and liquid phases based on the phasic volume fraction, which is the same as that usedin the SPACE code. The constitutive equations for the interfacial drag force are also identified. Based onthe assessments, the Rassame-Hibiki correlation, Hibiki-Ishii correlation, Ishii-Zuber correlation, andRassame-Hibiki correlation are recommended for computing the distribution parameter, interfacial areaconcentration, drag coefficient, and relative velocity covariance of a horizontal bubbly flow, respectively.

Climate Change and its Impact on the Agricultural Sector

( Akira Hibiki ) 한국환경경제학회·한국자원경제학회(구 한국환경경제학회) 2018 한국환경경제학회 학술발표논문집 Vol.2018 No.하계

Empirical study on the impact of PM₁₀ on mortality rate in China

( Ding Lin ),( Akira Hibiki ) 한국환경경제학회·한국자원경제학회(구 한국환경경제학회) 2018 한국환경경제학회 학술발표논문집 Vol.2018 No.하계

This paper investigates the impact of PM₁₀ on mortality throughout 31 provinces in China by using dynamic panel data model. The results show PM₁₀ has significant negative impact on mortality rate in the long term. Higher income reduces the mortality rate, as well as reduces the impact of PM₁₀ on mortality rate. Provinces with higher increasing rate in PM₁₀ bring out more increasing in mortality rate. With increasing in PM₁₀ by 0.01 mg/m³ (6.9%, 24.61%), death toll will be increased by at most 0.2188 per thousand people. If the government adopt measures to reduce PM₁₀ concentration, the death toll is reduced by (285679.09, 370132.46) for reaching Chinese national standard and (1218762.97, 1549211.57) for WHO’s standard.

Formulation of time and volume averaged two-fluid model considering structural materials in a control volume

Lee, Sang Yong,Hibiki, Takashi,Ishii, Mamoru Elsevier 2009 Nuclear engineering and design Vol.239 No.1

<P><B>Abstract</B></P><P>Time–volume averaged two-fluid model considering structural materials in a control volume (porous media approach) is formulated for two-phase flow analyses. The time–volume averaged two-fluid model is obtained rigorously by averaging local time-averaged two-fluid model over a control volume including structural materials. The volume porosity based model obtained by the simple time–volume averaging is converted into the surface porosity based model by introducing the directional surface porosity concept. The covariance approach is adopted to consider distributions of various variables in the control volume. The obtained porous media formulation is consistent with existing two-fluid model. Existing constitutive equations may be applicable to the porous media formulation provided they are properly time–volume averaged in the control volume. The strategy to obtain time–volume averaged constitutive equations is briefly discussed.</P>

Neurotoxicity and behavioral deficits associated with Septin 5 accumulation in dopaminergic neurons

Son, Jin H.,Kawamata, Hibiki,Yoo, Myung S.,Kim, Dae J.,Lee, Young K.,Kim, SooYoul,Dawson, Ted M.,Zhang, Hui,Sulzer, David,Yang, Lichuan,Beal, M. Flint,DeGiorgio, Lorraine A.,Chun, Hong S.,Baker, Harri Raven Press [etc.] 2005 Journal of neurochemistry Vol.94 No.4

<P>Abstract</P><P>Septin 5, a parkin substrate, is a vesicle- and membrane-associated protein that plays a significant role in inhibiting exocytosis. The regulatory function of Septin 5 in dopaminergic (DAergic) neurons of substantia nigra (SN), maintained at relatively low levels, has not yet been delineated. As loss of function mutations of parkin are the principal cause of a familial Parkinson's disease, a prevailing hypothesis is that the loss of parkin activity results in accumulation of Septin 5 which confers neuron-specific toxicity in SN-DAergic neurons. <I>In vitro</I> and <I>in vivo</I> models were used to support this hypothesis. In our well-characterized DAergic SN4741 cell model, acute accumulation of elevated levels of Septin 5, but not synphilin-1 (another parkin substrate), resulted in cytotoxic cell death that was markedly reduced by parkin co-transfection. A transgenic mouse model expressing a dominant negative parkin mutant accumulated moderate levels of Septin 5 in SN-DAergic neurons. These mice acquired a progressive <SMALL>L</SMALL>-DOPA responsive motor dysfunction that developed despite a 25% higher than normal level of striatal dopamine (DA) and no apparent loss of DAergic neurons. The phenotype of this animal, increased striatal dopamine and reduced motor function, was similar to that observed in parkin knockout animals, suggesting a common DAergic alteration. These data suggest that a threshold level of Septin 5 accumulation is required for DAergic cell loss and that <SMALL>L</SMALL>-DOPA-responsive motor deficits can occur even in the presence of elevated DA.</P>

Characteristics of Bubble Departure Frequency in a Low-Pressure Subcooled Boiling Flow

EUH, Dongjin,OZAR, Basar,HIBIKI, Takashi,ISHII, Mamoru,SONG, Chul-Hwa Atomic Energy Society of Japan 2010 Journal of nuclear science and technology Vol.47 No.7

<P>In order to measure the bubble departure frequency, a flow visualization system was set up on a vertical annulus test section with a heater rod by using a high-speed camera. In this study, we developed an efficient methodology of image processing for obtaining the bubble departure frequency data. Bubble nucleation was investigated under various thermal hydraulic conditions of water, which correspond to pressures from 167 to 346 kPa, mass fluxes from 214 to 1869 kg/m<SUP>2</SUP>s, heat fluxes from 61 to 238 kW/m<SUP>2</SUP>, and subcooling degrees from 7.5 to 23.4 K. The characteristics of bubble departure frequency were analyzed with the present data. The measured data was compared with models available in existing literature and a more plausible model was proposed.</P>

Examination of the extinction coefficient in the Beer–Lambert law for an accurate estimation of the forest canopy leaf area index

Taku M. Saitoh,Shin Nagai,Hibiki M. Noda,Hiroyuki Muraoka,Kenlo Nishida Nasahara 한국산림과학회 2012 Forest Science And Technology Vol.8 No.2

Leaf area index (LAI) is a crucial ecological parameter that represents canopy structure and controls many ecosystem functions and processes, but direct measurement and long-term monitoring of LAI are difficult, especially in forests. An indirect method to estimate the seasonal pattern of LAI in a given forest is to measure the attenuation of photosynthetically active radiation (PAR) by the canopy and then calculate LAI by the Beer–Lambert law. Use of this method requires an estimate of the PAR extinction coefficient (k), a parameter needed to calculate PAR attenuation. However, the determination of k itself requires direct measurement of LAI over seasons. Our goals were to determine (1) the best way to model k values that may vary seasonally in a forest, and (2) the sensitivity of estimates of canopy ecosystem functions to the errors in estimated LAI. We first analyzed the seasonal pattern of the ‘‘true’’ k (k_p) under cloudy and sunny conditions in a Japanese deciduous broadleaved forest by using the inverted form of the Beer–Lambert law with the true LAI and PAR. We next calculated the errors of PAR-based LAIs estimated with an assumed constant k (LAI_pred) and determined under what conditions we should expect k to be approximately constant during the growing period. Finally, we examined the effect of errors in LAI_pred on estimates of gross primary production (GPP), net ecosystem production (NEP), and latent heat flux (LE) calculated with a land-surface model using LAI_pred as an input parameter. During the growing period, cloudy kp varied from 0.47 to 1.12 and sunny kp from 0.45 to 1.59. Results suggest that the value of LAI_pred was adequately estimated with the k_p obtained under cloudy conditions during the fully-leaved period (0.53–0.57). However, LAI_pred was overestimated by up to 0.6 m2 m–2 inMay and November. The errors in LAIpred propagated to errors in modeled carbon and latent heat fluxes of –0.21 to 0.32 g C m^–2 day^–1 in GPP, –0.09 to 0.19 g C m^–2 day^–1 in NEP, and –3.2 to 3.9 Wm^–2 in LE, which is close to the measurement errors recognized in the tower flux measurement. LAI_pred estimated with an assumed constant k can be useful for some ecosystem studies as a second-best alternative if k is equated to the value of k_p measured under cloudy conditions especially during the fully-leaved period.

The recreational value of coral reefs in Okinawa Prefecture: A site choice model

( Katsuhito Nohara ),( Azusa Okagawa ),( Akira Hibiki ),( Hiroya Yamano ) 한국환경경제학회·한국자원경제학회(구 한국환경경제학회) 2018 한국환경경제학회 학술발표논문집 Vol.2018 No.하계

The coral reef ecosystems provide many goods and services to coastal populations, such as tourism. Furthermore, they form a unique natural ecosystem, with an important biodiversity value as well as scientific and educational value. They also form a natural protection against wave erosion. However, they have been damaged due to red soil erosion and global warming. Therefore, the preservation of coral reefs has been an important policy issue. The cost-benefit analysis is important for choosing cost-effective policies. Although a few studies have evaluated the economic value of coral reefs in Okinawa Prefecture, Japan, most of them have applied the contingent valuation method. The purpose of this study is to employ the discrete choice travel cost method to estimate the value of coral reefs that is obtained by visitors to Okinawa prefecture. We conducted an on-site survey of visitors at Naha airport, New Ishigaki airport and Miyako airport on 8 November to 11 in 2013 and collected 410 responses. We applied the conditional logit model to tourist’s decision to select his/her destination and estimate the model using collected data. Based on the conditional logit model, the hypothesis of independence from irrelevant alternatives (IIA) cannot be rejected. We also tried to apply the mixed logit model to our data but there was no significant difference between random parameters and nonrandom ones. The main finding is that the marginal willingness to pay by a tourist for coral reefs is 4,754 yen/km2 per day and 16,544 yen/㎢ per trip.

Flow Structure of Subcooled Boiling Water Flow in a Subchannel of 3×3 Rod Bundles

YUN, Byong-Jo,PARK, Goon-Cherl,JULIA, J. Enrique,HIBIKI, Takashi Atomic Energy Society of Japan 2008 Journal of nuclear science and technology Vol.45 No.5

<P>In this paper, the interfacial flow structure of subcooled water boiling flow in a subchannel of 3×3 rod bundles is presented. The 9 rods are positioned in a quadrangular assembly with a rod diameter of 8.2 mm and a pitch distance of 16.6 mm. Local void fraction, interfacial area concentration, interfacial velocity, Sauter mean diameter, and liquid velocity have been measured using a conductivity probe and a Pitot tube in 20 locations inside one of the subchannels. A total of 53 flow conditions have been considered in the experimental dataset at atmospheric pressure conditions with a mass flow rate, heat flux, inlet temperature, and subcooled temperature ranges of 250–522 kg/m<SUP>2</SUP> s, 25–185 kW/m<SUP>2</SUP>, 96.6–104.9°C, and 2–11 K, respectively. The dataset has been used to analyze the effect of the heat flux and mass flow rate on the local flow parameters. In addition, the area-averaged data integrated over the whole subchannel have been used to validate some of the distribution parameter and drift velocity constitutive equations and interfacial area concentration correlations most used in the literature.</P>

Axial Development of Flow Regime in Adiabatic Upward Two-Phase Flow in a Vertical Annulus

Julia, J.E.,Ozar, B.,Dixit, A.,Jeong, J.-J.,Hibiki, T.,Ishii, M. AMERICAN SOCIETY MECHANICAL ENGINEERS 2009 Journal of fluids engineering Vol.131 No.2