RELAP-7 Theory Manual

Berry, Ray A.; Zou, Ling; Zhao, Haihua; Zhang, Hongbin; Peterson, John W.; Martineau, Richard; Kadioglu, Samet Y.; Andrš, David

doi:10.2172/1262488

Cited by 39 publications

(74 citation statements)

References 33 publications

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“…The two-fluid seven-equation two-pressure model used in this paper is summarized as follows [16,22,23,46], which allows for a change of the pipeline cross section [34].…”

Section: Two-fluid Two-pressure Mathematical Modelmentioning

confidence: 99%

“…Using the volume fraction propagation as a basic conservation equation is widely used because it changes the structure of conservation equation system and makes seven-equation model unconditionally hyperbolic (well-posed) in the sense of Hadamard [15]. In recent years, the development of advanced thermalhydraulics system analysis codes has aroused great interest such as RELAP-7 [16], NEPTUNE project [17], CASL [18], and CATHARE-3 [19]. RELAP7 code developed by the Idaho National Laboratory is ongoing now.…”

Section: Introductionmentioning

confidence: 99%

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Implementation and Comparison of High-Resolution Spatial Discretization Schemes for Solving Two-Fluid Seven-Equation Two-Pressure Model

Wu¹,

Chao²,

Wu³

et al. 2017

Science and Technology of Nuclear Installations

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As compared to the two-fluid single-pressure model, the two-fluid seven-equation two-pressure model has been proved to be unconditionally well-posed in all situations, thus existing with a wide range of industrial applications. The classical 1st-order upwind scheme is widely used in existing nuclear system analysis codes such as RELAP5, CATHARE, and TRACE. However, the 1st-order upwind scheme possesses issues of serious numerical diffusion and high truncation error, thus giving rise to the challenge of accurately modeling many nuclear thermal-hydraulics problems such as long term transients. In this paper, a semiimplicit algorithm based on the finite volume method with staggered grids is developed to solve such advanced well-posed twopressure model. To overcome the challenge from 1st-order upwind scheme, eight high-resolution total variation diminishing (TVD) schemes are implemented in such algorithm to improve spatial accuracy. Then the semi-implicit algorithm with high-resolution TVD schemes is validated on the water faucet test. The numerical results show that the high-resolution semi-implicit algorithm is robust in solving the two-pressure two-fluid two-phase flow model; Superbee scheme and Koren scheme give two highest levels of accuracy while Minmod scheme is the worst one among the eight TVD schemes.

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“…The two-fluid seven-equation two-pressure model used in this paper is summarized as follows [16,22,23,46], which allows for a change of the pipeline cross section [34].…”

Section: Two-fluid Two-pressure Mathematical Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Implementation and Comparison of High-Resolution Spatial Discretization Schemes for Solving Two-Fluid Seven-Equation Two-Pressure Model

Wu¹,

Chao²,

Wu³

et al. 2017

Science and Technology of Nuclear Installations

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“…Nowadays, many research projects place their interests in the development of advanced next-generation T-H codes, such as CATHARE-3, 7 NEPTUNE, 8 and RELAP-7. 9 There are three important ideas to overcome the ill-posed nature of two-fluid six-equation model and obtain the corresponding well-posed numerical algorithm in the open literature. The implementation of the interfacial pressure term was adopted in the CATHARE code 10 and the implementation of the virtual mass force term was adopted in the RELAP5 code.…”

Section: Introductionmentioning

confidence: 99%

“…Due to the fact that the two-pressure model is well posed in all situations, many researchers have devoted themselves to the study of two-pressure model since 1976. [12][13][14][15][16][17][18][19][20][21][22][23] As compared to the six-equation one-pressure model, the two-pressure model supplements the additional volume fraction propagation equation as the seventh conservation equation. Volume fraction equation is widely used as a basic conservation equation because it changes the structure of the conservation equation system and make the two-pressure model unconditionally well posed.…”

Section: Introductionmentioning

confidence: 99%

Development of temporal and spatial high‐order schemes for two‐fluid seven‐equation two‐pressure model and its applications in two‐phase flow benchmark problems

Chao

Liu

Shan

et al. 2018

Numerical Methods in Fluids

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Summary Current existing main nuclear thermal‐hydraulics (T‐H) system analysis codes, such as RALAP5, TRACE, and CATHARE, play a crucial role in the nuclear engineering field for the design and safety analysis of nuclear reactor systems. However, two‐fluid model used in these T‐H system analysis codes is ill posed, easily leading to numerical oscillations, and the classical first‐order methods for temporal and special discretization are widely employed for numerical simulations, yielding excessive numerical diffusion. Two‐fluid seven‐equation two‐pressure model is of particular interest due to the inherent well‐posed advantage. Moreover, high‐order accuracy schemes have also attracted great attention to overcome the challenge of serious numerical diffusion induced by low‐order time and space schemes for accurately simulating nuclear T‐H problems. In this paper, the semi‐implicit solution algorithm with high‐order accuracy in space and time is developed for this well‐posed two‐fluid model and the robustness and accuracy are verified and assessed against several important two‐phase flow benchmark tests in the nuclear engineering T‐H field, which include two linear advection problems, the oscillation problem of the liquid column, the Ransom water faucet problem, the reversed water faucet problem, and the two‐phase shock tube problem. The following conclusions are achieved. (1) The proposed semi‐implicit solution algorithm is robust in solving two‐phase flows, even for fast transients and discontinuous solutions. (2) High‐order schemes in both time and space could prevent excessive numerical diffusion effectively and the numerical simulation results are more accurate than those of first‐order time and space schemes, which demonstrates the advantage of using high‐order schemes.

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“…However, a temporal accuracy study was only performed for a linear advection case, and for the other test cases the 'basic' two-fluid model (without level gradient terms) was used, which is unconditionally ill-posed. Also the commercial nuclear safety code RELAP-7 ( Berry et al, 2015 ) advises BDF2 as the time integration method. However, almost no details are given on the stability, accuracy and damping properties of the numerical time integration method.…”

Section: Introductionmentioning

confidence: 99%

Analysis of time integration methods for the compressible two-fluid model for pipe flow simulations

Sanderse

Smith

Hendrix

2017

International Journal of Multiphase Flow

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In this thesis, a 7-field Lagrangian slug capturing and slug tracking model with higher order methods and an adaptive grid is investigated for predicting the behaviour of two-phase gasliquid flow in multiphase flow pipelines. The model is capable of simulating both compressible and incompressible slugs, and pigs. The model has the possibility to simulate gas-liquid flow, including a liquid droplet field in the gas and entrained gas in the liquid.Walls consisting of multiple layers of different materials can be added to the pipes, and the energy equations for both the pipe walls and the fluids are solved. The mass, momentum and energy equations are solved in an iterative manner. Several additional tools and features have also been developed, like a steady state solver for the velocity, holdup, pressure and temperature, a unit-cell model which can be used as a standalone tool or as a sub-grid model in the dynamic model, fully period boundary conditions, curved pipe geometry, usage of tabulated PVT-files, and modelling of interfacial mass transfer. Higher order schemes are available for both spatial and temporal discretization. Different details in the two-fluid model have also been investigated, amongst other how to handle changes in the pipe cross-sectional area correctly for the border movement and level gradient. It is also shown how the upwind velocity must be modified by scaling factors to obtain the correct Bernoulli effect in the case of incompressible flow.The work resulted in four papers. In Paper 1 the model was tested against large scale experimental data, and was shown to give good predictions of the slugging periods after including a liquid droplet field and including the separator in the simulations. In Paper 3 the slug capturing capabilities of the model are tested against experimental data from a medium Furthermore I want to thank Jon Harald Kaspersen, my superior at SINTEF Petroleum, who allowed me to take a partial absence of leave in order to do this work. ..................................................................................................................... 92 2.9.7 Generic equation class ................................................................................................................ IntroductionIn the petroleum industry, multiphase flow occurs when transporting oil and gas (and possibly water) in the same pipe through long multiphase pipeline systems. The behaviour of the flow can take many forms (flow patterns), depending on several parameters like fluid velocities, pipe diameter, pipe inclination, and the fluid properties. The fluid properties are again dependent on the pressure and temperature in the system, especially the gas density and the fluid viscosity. Certain flow patterns can cause significantly reduced production, or even such operational challenges that the pipeline must be abandoned. It is therefore of crucial importance to be able to predict the behaviour of the flow when investigating how to design the pipeline. The simplest of the...

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RELAP-7 Theory Manual

Cited by 39 publications

References 33 publications

Implementation and Comparison of High-Resolution Spatial Discretization Schemes for Solving Two-Fluid Seven-Equation Two-Pressure Model

Implementation and Comparison of High-Resolution Spatial Discretization Schemes for Solving Two-Fluid Seven-Equation Two-Pressure Model

Development of temporal and spatial high‐order schemes for two‐fluid seven‐equation two‐pressure model and its applications in two‐phase flow benchmark problems

Analysis of time integration methods for the compressible two-fluid model for pipe flow simulations

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