Transient Calculations Research Articles

Numerical study of blowdown period of double-end break loss of coolant accident in PWR based on RELAP5

Loss of coolant accident (LOCA) is one of the most severe accidents of nuclear power plants (NPP). During the early blowdown period, the system is in a high-pressure gradient and high-velocity gradient state. Therefore, the hydrodynamic forces and safety analysis are highly related to calculating thermal-hydraulic parameters in the flow field. This paper studied the factors and modeling methods that affect the calculation of thermal-hydraulic characteristics under large break LOCA conditions. Firstly, the reactor core and primary system of a typical two-loop pressurized water reactor (PWR) NPP is modeled using the system analysis code RELAP5 Mod4.0. The normal operation state is obtained after the steady calculation. Then, transient calculation of double-end break LOCA is implemented considering the effects of break opening time and the pressurizer. The influence of the results on the calculation of hydrodynamic force has also been analyzed. Finally, the modeling method of reactor pressurized vessel (RPV) downcomer is presented. It is found that the flow field can be better simulated when the downcomer is modeled with parallel channels and several transverse junctions. Thus, this paper provides meaningful suggestions for modeling and simulation in the early blowdown period under LOCA conditions and contributes to further hydrodynamic load calculation and reactor safety analysis.

Investigation of low-temperature NO2 reduction by NH3 over activated carbon: Effect of pore structure and flue gas conditions

NO2–NH3 selective catalytic reduction (SCR) over activated carbon (AC) is a potential deNOx method at low temperatures. In this study, a series of AC samples with developed pore structures were prepared through CO2 activation. DeNOx activity tests indicated that the increase in specific surface area enhanced NOx conversion and decreased the temperature corresponding to the highest NOx conversion. FGAC900, which had the highest specific surface area, showed the highest NOx conversion of 97.80% at 150 °C. The influence of various flue gas conditions was also investigated. O2 concentrations in the range of 0–20 vol% had little effect on NOx conversion. The appropriate gas hourly space velocity and NH3 concentration are important for achieving superior deNOx performance. When 8 vol% H2O was added into dry simulated flue gas at 150 °C, NOx conversion decreased from 97.80% to 90.71%. Transient response experiments and density functional theoretical calculation results showed that the inhibition of H2O is reversible and results from competitive physisorption between NO2 and H2O molecules. The in situ DRIFT results indicated that NH4NO3 is an important intermediate. An efficient deNOx AC catalyst with a developed pore structure was prepared, and the effects of flue gas conditions were systematically investigated.

The Super Thermal Conductivity Model for High-Temperature Heat Pipe Applied to Heat Pipe Cooled Reactor

Differing from the traditional Pressurized Water Reactor (PWR), heat pipe cooled reactor adopts the high-temperature heat pipes to transport fission heat generated in the reactor core. Therefore, the basis of coupling calculation on this type of reactor system is to have a suitable model for high-temperature heat pipe simulation. Not only is it required that this model can well describe the transient characteristics of heat pipe, but it should be simple enough to reduce the computational resource. In this paper, the super thermal conductivity model (STCM) for high-temperature heat pipe is proposed for this purpose. In this model, heat transport of vapor flow is simplified as high efficiency heat conductance. Combined with the network method, the evaporation rate, the condensation rate, and the flow rate in the wick region can be preliminarily obtained. Using recommended equations to calculate the heat transfer limitation, this model can realize the safety judgment of heat pipe. The heating system for high-temperature heat pipe is established to validate this model. The heating experiments with different heating powers is tested. Then, this model is applied on the numerical calculation of Kilowatt Reactor Using Stirling TechnologY (KRUSTY) reactor. In the steady state calculation, the results show that the temperature distribution on contact surface between fuel and heat pipe is nonuniform, which will lead to higher peak temperature and temperature difference for the reactor core. In the transient calculation, the load-following accident is chosen. Comparing with the experimental results, the applicability of the proposed model on heat pipe cooled reactor is verified. This model can be used for heat pipe cooled reactor simulation.

Prediction of the Impact of Air Speed Produced by a Mechanical Fan and Operative Temperature on the Thermal Sensation

Natural ventilation associated with a mechanical fan is a feasible strategy to enhance thermal acceptability in warm weather. The ASHRAE-55 provides the increase for operative temperature proportional to the increase in air speed while maintaining thermal comfort. Conversely, the range of informed values is limited and little guidance for mechanical fans is provided. This work explores the relationship between operative temperature and air speed produced by ceiling fans, and the effectiveness to deliver thermal comfort for a wider range of values. The research method comprises transient computer fluid dynamics simulations coupled with a thermal sensation model and is divided into two stages: a calibration exercise and a parametrical investigation. Three matrices are presented for a range of operative temperatures (21.0–36.0 °C) and air speeds (0–2.5 m/s) for: Dynamic Thermal Sensation (DTS) (a computer-based seven-point index), Predicted Percentage of Dissatisfied, and potential Cooling Effect. When compared to the Predicted Mean Vote, the DTS overestimates thermal comfort for temperatures under 28.0 °C with increased air speed and overestimates discomfort for temperatures above 31.0 °C, even with increased air speed. Agreement is found between both scales for 28.0–31.0 °C, defining a range for the effective use of ceiling fans to provide thermal comfort under warm weather conditions.

Study on the temperatures of railway tunnel side ditches in high-latitude cold regions based on the effects of wind

Tunnel side ditches in the high-latitude cold regions of China experience severe freezing-induced damage. In this paper, a three-dimensional transient temperature calculation model for tunnel in cold area is proposed, and the reliability of the temperature calculation model is verified by the field test results. The characteristics of tunnel temperature distribution under the influence of many factors, especially tunnel section and tunnel length, which are ignored in the existing research, are studied. The influence of tunnel design parameters on temperature field under different railway tunnel types (single-track and double-track tunnel) was also studied. The results show that the length with a temperature below 0 °C of single-track tunnel increases with the increase of tunnel length, while that of double-track tunnel decreases. No matter what type of tunnel, increasing the train frequency and train speed can significantly increase the freezing range of the tunnel. However, the influence of piston wind on temperature distribution in single-track tunnel and double-track tunnel is very different. For single-track tunnel, the growth rate of the length with a temperature below 0 °C decreases with the increase of train speed; However, for double-track tunnel, the growth rate of the length with a temperature below 0 °C increases with train speed. The frost damage of double-track tunnel in cold area is more serious than that of single-track tunnel. Under the same conditions, the antifreezing length of double-track tunnel is much longer than that of single-track tunnel. Based on the calculation results, a prediction model for the freezing length of cold-region tunnel side ditches was proposed, thereby providing a reference for the prevention and control of freezing-induced damage in the side ditches of cold-region tunnels.

Effect of outlet impeller diameter on performance prediction of centrifugal pump under single-phase and cavitation flow conditions

Abstract In this current study, the transient numerical calculations using CFD code are carried out under different outlet impeller diameters for the flow field within a centrifugal pump under single-phase and cavitation conditions. Both qualitative and quantitative analyses are carried out on all of these results in order to better understand the flow structure within a centrifugal pump. Also, the investigations using different outlet impeller diameters configurations relating to the static pressure, velocity magnitude, vapour volume fraction variations, as well as pressure fluctuations in both time and frequency domain at the impeller and volute of the pump are analysed. Velocity and static pressure variations of the pump under different outlet impeller diameters range (200, 210 and 220 mm) are investigated. Reliable model is developed and validated, at various pump operating conditions, to analyse the characteristics of pressure fluctuations in both time and frequency domain. Cavitation occurrence, under different outlet impeller diameters and flow rates, are detected and correlated, using a CFD model (volume fraction distributions). Based on the developed model’s findings, at the set operating conditions ranges, the distribution and impact (cavitation and head-wises) of both the pressure and velocity are analysed. The average pressure fluctuation in the volute for do = 210 mm is higher than for do = 200 mm by about 6.74%, also the maximum pressure fluctuation for do = 220 mm is higher than for do = 210 mm by around 7.4%. Furthermore, the maximum pressure fluctuation in the impeller for do = 210 mm is higher than for do = 200 mm by 12.48%, also for do = 220 mm is higher than for do = 210 mm by 10.8%. The developed CFD models are proved valuable tools in identifying and optimizing the pump performance and characterization. The head for when do = 220 mm is higher than for when do = 200 mm under both single-phase and cavitation conditions by around 14.13% and 14.69%. The maximum pressure fluctuation for do = 200 mm is lower than for do = 210 mm by 41.58%. Furthermore, the maximum pressure fluctuation at the impeller for do = 220 mm is higher than the two models. There is a small clearance between the impeller and the volute for this model, leading to the pressure fluctuation amplitudes being higher than the other above models.

Transient computer simulation of the temperature profile in different packaging materials: An optimization of thermal treatment of tender coconut water

AbstractUnderstanding the temperature profile of different packaging materials would be useful for selecting appropriate packaging material for in‐bottle pasteurization. The temperature profile of polypropylene, polyethylene (PE), and polyethylene terephthalate bottles was investigated using COMSOL Multiphysics software to understand the temperature–time correlation with thermal treatments. PE bottles exhibited the least temperature difference between cold and hot spots. Optimization of thermal treatment processing parameters such as temperature (80–95°C) and treatment time (5–15 min) for inactivation of enzymes, namely polyphenol oxidase (PPO) and peroxidase (POD), in tender coconut water (TCW) was performed to the extent its shelf life. The quality parameters of heat‐treated TCW such as pH, total soluble solids (TSS), titratable acidity (TA), turbidity, phenolic content, PPO, POD, and sensory evaluation were analyzed. The multiple linear regression models were developed for each quality parameter using a central composite design (CCD). The optimized treatment conditions were 84°C temperature and 5 min treatment time with the desirability of 0.926. The responses recorded were pH = 5.4, TSS = 5.52, turbidity = 7.1 NTU, TA = 0.06% of malic acid, relative PPO = 0.099, relative POD = 0.093, phenolic content = 44.712 mg gallic acid equivalent/L, and overall acceptability score = 8.Practical ApplicationsUnderstanding the temperature profile of different packaging materials during pasteurization or sterilization is imperative to select the suitable packaging material, and also it would be helpful for designing the heating system. Tender coconut water (TCW) is the most popular natural drink in Asian countries. However, the pasteurization conditions are yet to be optimized to preserve TCW without affecting its bioactive and functional components. The current practice followed for in‐bottle sterilization of TCW is polyethylene terephthalate (PET). This is due to PET being cheaper and readily available than other packaging materials. However, the quality of the TCW could affect PET due to improper heat distribution which can lead to damage of bioactive components. The present study has optimized the suitable pasteurization conditions and packaging material for bottling and marketing TCW. The findings of the present study will boost the market potential of the tender coconut processing industries.

1,2,3-Tri(9-anthryl)benzene: Photophysical Properties and Solid-State Intermolecular Interactions of Radially Arranged, Congested Aromatic π-Planes.

We report the Negishi coupling based synthesis of 1,2,3-tri(9-anthryl)benzene derivatives containing three radially arranged anthracenes in a π-cluster. In the crystalline state of the unsubstituted derivative, intermolecular π-π and CH-π interactions between the anthracene units drive the formation of the two-dimensional packing structure. Owing to though-space π-conjugation between anthracene units, the substances have unique electronic properties. The excited-state dynamic behavior occurring between the three anthracene moieties, such as exciton localization/delocalization, was elucidated by means of transient absorption measurements and quantum chemical calculations. Interestingly, even though the three anthracenes are closely oriented with approximately 3.0 Å between their C-9 positions, exciton localization on two anthracene units is energetically favorable because of the flexible nature of the radially arranged aromatic rings.

Electromagnetic transients in the control system of output parameters of a solar power plant in Tajikistan Central Asia region

At present, as the demand for electricity increases in all sectors, there is an urgent need to introduce alternative renewable energy sources into modern energy systems. Renewable energy sources, which consist of solar (photovoltaic, PV), wind and hydro power, are key alternative sources of “green energy’’ energies, but it can also be used to produce “green” hydrogen. Thanks to scientific and technological progress, the cost of photovoltaic solar radiation converters is constantly decreasing at a high rate, which makes it possible to build solar power plants of sufficiently large capacity. In the coming decades, solar energy will become an incentive for the economic development of countries that have the maximum “solar” resource. The Republic of Tajikistan is one of these countries with a high potential for solar energy.The article presents an analysis of the resources and potential of solar energy in the Republic of Tajikistan. The study of electromagnetic transients in networks with photovoltaic solar power plants is performed. The main equations, simulation model and calculations of transients are presented, taking into account changes in voltage on DC buses. An algorithm for controlling the system of automatic control of output parameters is proposed. The analysis of dynamic and static modes in parallel operation of a solar power plant with the grid is carried out. A block diagram and computer model is constructed in the MATLAB package together with Simulink and Power System Blockset.

The equivalent for the global energy interconnection for transient stability calculations

The equivalent for the global energy interconnection for transient stability calculations

Revealing the sensing mechanism of a fluorescent pH probe based on a bichromophore approach.

Fluorescence sensing plays an increasingly important role in biology and biomedicine. For many practical applications of fluorescent probes, an "off-on" response is preferred. The question of how fluorescence quenching/enhancement occurs is fundamental and of high importance for application and design of new fluorescent probes. The sensing mechanism of an aminorhodamine (TMARh) pH probe is investigated using femtosecond transient absorption spectroscopy and quantum chemical calculations, showing that this probe is best understood using the bichromophore model rather than the more common models such as photoinduced electron transfer or intramolecular charge transfer. Under excitation in the main absorption band at 530 nm, a fast internal conversion to the first excited state (S1) is observed for TMARh; meanwhile, no new transient components are obtained when TMARh is excited directly to S1 in the weakly absorbing red tail at 630 nm. It is confirmed that the S1 of TMARh is a dark "off" state. Theoretical calculations show that the S1 "off" state is an intramolecular charge transfer state from an aminophenyl group to a rhodamine chromophore. After protonation of the aminophenyl group, to yield HTMARh, the transient S2/S1 internal conversion process that occurs in TMARh under 530 nm excitation is absent, suggesting that the charge transfer state becomes highly unfavorable. All calculations and spectral data confirm that HTMARh has localized transition in the rhodamine chromophore, in agreement with this being the bright "on" state of the pH probe. The current work not only provides a photophysical insight into the sensing mechanism of this specific probe, but also shows that the bichromophore model is useful and may be relevant for analyzing other probes or in the designing of new ones.

Wind generator transient response analysis and improvement using BESS

Transient stability is very important for safety in the power system. In this paper, transient stability analysis of a wind power generator connected to distribution network is presented. The analysis was performed on a model of a realistic 12-bus system. In order to improve transient response capabilities of the system, battery energy storage system (BESS) is included in the simulations. It was demonstrated that BESS has significant influence on the stability of the network during the fault conditions. All simulations were performed in the DigSILENT Power Factory software. The analysis and assessment of the network was performed for the case of three-phase symmetrical fault with all lines in service and following a single line outage (failure and N-1 criterion). The results show that the connection of the wind generators to distribution network depends on the distance from the primary source of the grid (slack bus). However, BESS system can be used to improve transient stability response in which case distance from the primary source station is not critical. Also, this analysis adds additional evidence on the importance of transient stability calculations during the process of new generator unit connection to the power system.

Solvent dependent triplet state delocalization in a co-facial porphyrin heterodimer.

The excited triplet state of a cofacial aluminum(III) porphyrin-phosphorus(V) porphyrin heterodimer is investigated using transient EPR spectroscopy and quantum chemical calculations. In the dimer, the two porphyrins are bound covalently to each other via a μ-oxo bond between the Al and P centres, which results in strong electronic interaction between the porphyrin rings. The spin polarized transient EPR spectrum of the dimer is narrower than the spectra of the constituent monomers and the magnitude of the zero-field splitting parameter D is solvent dependent, decreasing as the polarity of the solvent increases. The quantum chemical calculations show that the spin density of the triplet state is delocalized over both porphyrins, while magnetophotoselection measurements reveal that, in contrast to the value of D, the relative orientation of the ZFS axes and the excitation transition dipole moments are not solvent dependent. Together the results indicate that triplet state wavefunction is delocalized over both porphyrins and has a modest degree of charge-transfer character that increases with increasing solvent polarity. The sign of the spin polarization pattern of the dimer triplet state is opposite to that of the monomers. The positive sign of D predicted for the monomers and dimer by the quantum chemical calculations implies that the different signs of the spin polarization patterns is a result of a difference in the spin selectivity of the intersystem crossing.

Comparative structural and frictional analyses on various lightweight materials for aircraft disc brake

Aircraft brakes are an essential system that is used to control the motion of the aircraft. Various types of aircraft have been used in the past years depending on factors like the weight of the aircraft, landing speed, etc. The material selection for the aircraft disc is an important step as it determines the lifetime of the brake assembly and its performance. The main problem faced is the friction and the accompanying huge amount of heat developed when the disc and pin encounter each other. Various materials have been considered for disc and frictional analysis was performed for each material. The equivalent stress, shear stress, and total deformation contours have been compared. This analysis will prove useful in determining a better material for disc brakes. In this regard, various lightweight materials are considered for the comparative transient structural computations such as Carbon Fiber Reinforced Polymer [CFRP], Glass Fiber Reinforced Polymer [GFRP], and Kevlar Fiber Reinforced Polymer [KFRP]. An unique rotating disc is modeled based on the literature survey and thereby the computational composite model is constructed with the help of ANSYS Composite preprocessor tool. The working conditions are used at the phase of landing and thereby the maximum RPM is given as the external load for this computation. Based on low deformation and frictional stress generation, the CFRP is most suitable for all kind of environments and all kind of aircraft.

Transient Simulation and Optimization of Regional Integrated Energy System

A modeling method of regional integrated energy system based on bus method and transient simulation is proposed, and the system optimization is based on the dynamic balance of supply and demand in the whole year energy supply cycle. A CCHP system of gas turbine coupled with ground source heat pump and electric refrigeration unit is constructed. The energy relationship of the system is described by bus structure, and the transient calculation model is built on TRNSYS platform. The weighted sum of annual total cost saving rate, primary energy saving rate and environmental pollutant shadow cost saving rate is taken as the optimized objective function, and on the basis of annual dynamic balance, the Hooke-Jeeves algorithm is used for optimization of the system configuration. A complex commercial area in Beijing is taken as an example, and different weighting coefficients are set for optimization of the system configuration. The results show that, from the perspective of economy, environmental benefit and primary energy consumption, performance of the system increases and then decreases with rise of gas turbine power; under the simulated cooling/heating load, the maximum number of optimum configuration is seen in the combination of 35 kW gas turbine + 723 kW GSHP and 1178 kW electric chiller; in comparison with traditional distributed system, the annual cost saving rate, primary energy saving rate and environmental pollutant shadow cost saving rate of the system are 29.4%, 49.6% and 58.2%, respectively.

An improved analysis of the OECD/NRC PWR MOX/UO2 core transient benchmark with PARCS/Serpent

This paper presents an improved analysis of the OECD/NRC PWR MOX/UO2 core transient benchmark using the two-step method combining the Monte Carlo code Serpent 2 and nodal kinetics code PARCS. Analyses of the following important factors that can affect the PARCS/Serpent calculations were performed: diffusion coefficients attained with the B1 leakage corrected out-scatter approximation and cumulative migration method (CMM), reflector cross-sections generated with 1D and 3D reflector models, thermal cut-offs for two-group structure (0.625 eV, 1.3 eV, 2.02 eV and 4.0 eV), and nuclear data libraries (ENDF/B-VI.8, ENDF/B-VII.1 and ENDF/B-VIII.0). The results showed that using the CMM method and 3D reflector model alongside the 0.625 eV cut-off is the best choice while using the 4.0 eV cut-off or ENDF/B-VIII.0 library leads to the most conservative transient results. Thus, it is highly recommended that the two-step approach with PARCS/Serpent proposed be applied to improve further transient calculations of PWR MOX/UO2 cores.

Study on a New Transient Productivity Model of Horizontal Well Coupled with Seepage and Wellbore Flow

Digital transformation has become one of the major themes of the development of the global oil industry today. With the development of digital transformation, on-site production will surely achieve further automated management, that is, on-site production data automatic collection, real-time tracking, diagnosis and optimization, and remote control of on-site automatic adjustment devices. In this process, the realization of real-time optimization work based on massive data collection needs to be carried out combined with oil and gas well transient simulation. Therefore, research of the horizontal well capacity prediction transient model is one of the important basic works in the work of oil and gas digital transformation. In this paper, the method and process of establihing the transient calculation model of single-phase flow in horizontal wells are introduced in detail from three aspects: reservoir seepage, horizontal wellbore flow (taking one kind of flow as an example), and the coupling model of two flows. The model is more reliable through the verification of pressure recovery data from multiple field logs. The transient model of single-phase seepage in horizontal wells will lay the foundation for the establishment of transient models of oil-gas two-phase seepage and oil-gas-water three-phase seepage.

Insights into the Mechanism of an Allylic Arylation Reaction via Photoredox-Coupled Hydrogen Atom Transfer.

Despite widespread use as a synthetic method, the precise mechanism and kinetics of photoredox coupled hydrogen atom transfer (HAT) reactions remain poorly understood. This results from a lack of detailed kinetic information as well as the identification of side reactions and products. In this report, a mechanistic study of a prototypical tandem photoredox/HAT reaction coupling cyclohexene and 1,4-dicyanobenzene (DCB) using an Ir(ppy)3 photocatalyst and thiol HAT catalyst is reported. Through a combination of electrochemical, photochemical, and spectroscopic measurements, key unproductive pathways and side products are identified and rate constants for the main chemical steps are extracted. The reaction quantum yield was found to decline rapidly over the course of the reaction. An unreported cyanohydrin side product was identified and thought to play a key role as a proton acceptor in the reaction. Transient absorption spectroscopy (TAS) and quantum chemical calculations suggested a reaction mechanism that involves radical addition of the nucleophilic DCB radical anion to cyclohexene, with cooperative HAT occurring as the final step to regenerate the alkene. Kinetic modeling of the reaction, using rate constants derived from TAS, demonstrates that the efficiency of the reaction is limited by parasitic absorption and unproductive quenching between excited Ir(ppy)3 and the cyanohydrin photoproduct.

In situ preparation of two-dimensional ytterbium ions doped all-inorganic perovskite nanosheets for high-performance visual dual-bands photodetectors

Two-dimensional (2D) all-inorganic halide perovskites exhibit impressive optical and electrical properties, which are attracting extensive current interests. Rare earth (RE) ions doping is a significant method to adjust their optical, electrical properties and realize various applications. However, 2D RE ions-doped perovskite crystals have been rarely reported. Herein, we reported the synthesis of novel 2D all-inorganic perovskite CsPbClxBr3−x nanosheets (NSs) doped with RE ions. The octylamine (OLAm) with short carbon chains is used to tune the growth orientation for the preparation of 2D perovskite NSs. The morphology of the NSs can be adjusted by varying the ratio of shorter ligands to longer ligands and changing the temperature. The Yb3+ ions doped CsPbClBr2 NSs demonstrate an excitonic emission of perovskite host and a quantum cutting emission of Yb3+ ions at 985 nm with the optimal photoluminescence quantum yield (PLQY) of 128%. The results of femtosecond time-resolved transient absorption spectroscopy and DFT calculations indicate that the defect density of NSs is largely decreased and the photostability is enhanced induced by the passivation effect of Yb3+ ions. The photodetector (PD) based on lateral assembled Yb3+ ions doped CsPbClBr2 NS film is fabricated, which demonstrates a high responsivity and dual-band detection capability. The as-fabricated PDs are sensitive to both UV and NIR light, showing the responsivity of 1.96 A W−1, 0.12 mA W−1, the detectivity of 5 × 1012, 2.15 × 109 Jones at 440 nm and 980 nm, respectively. Finally, based on an imaging system with a PD array and a data analysis system, visual photoelectric detection is realized, and high-contrast images of the measured UV and NIR light are displayed. This work paves the way to tune the properties of 2D perovskite materials and develop high-performance optoelectronic devices.

A Method to Resolve Simulation of Discontinuous Flow Field: A Valve Example From Full Closing to Re-Closure

Abstract In transient computational fluid dynamics (CFD) simulations, the continuity of the flow field is an essential prerequisite. However, continuous flows can be separated under certain conditions, such as the process from valve opening to reclosure. The current method often leaves a narrow gap to estimate the full closing status, which will introduce a deviation. To address this issue, a full closing numerical simulation method (FCNSM) is developed to solve the problem of simulation between discontinuous flow field (DFF) and continuous flow field (CFF). The matrix laboratory (matlab) program has been used to communicate fluent as a server session to call the files fluent and automatically execute text-based user interface (TUI) commands. The radial basis function (RBF) is used to construct the relationship between the variables of the flow field and the coordinates of mesh nodes, which can achieve the data transmission from a DFF to a CFF. Automatic stopping of transient calculations is achieved by passing variables among matlab program, scheme language, and user-defined functions (UDF) when a physical quantity reaches a set value. Based on this method, a transient simulation with a dynamic mesh of a 2-D model regarding a pressure relief valve (PRV) is performed to simulate the process of the valve from full closing to reclosure, the flow characteristics through the PRV are obtained using this method. This study makes it possible to use FCNSM for understanding dynamic characteristics from DFF to CFF.