Transient Flow Field on Containment Floor Predicted by Two-Dimensional Shallow Equation Solver

2009 ◽  
Author(s):  
Young Seok Bang ◽  
Gil-Soo Lee ◽  
Byung-Gil Huh ◽  
Deog-Yeon Oh ◽  
Sweng-Woong Woo
Keyword(s):  
Flow Field ◽  
Transient Flow ◽  
Complex Geometry ◽  
Solid Wall ◽  
Shallow Water Equation ◽  
Water Reservoir ◽  
Two Dimensional ◽  
Pressurized Water ◽  
Fast Running ◽  
Propagation Of Waves

For the analysis of debris transport on containment floor, a model to predict the flow field should have a fast-running capability and high accuracy. A model is developed to calculate the transient flow field on the containment floor involving a complex geometry in the advanced pressurized water reactor (PWR) such as Advanced Power Reactor (APR)-1400, which does not have a switchover from injection to recirculation following a loss-of-coolant accident (LOCA). Two-dimensional shallow water equation (SWE) is solved using the finite volume method (FVM). Unstructured triangular meshes are used to simulate the complex structures on the containment floor. Harten-Lax-van Leer (HLL) scheme, one of the approximate Riemann solver, is adopted to capture the dry-wet interface and to determine the momentum flux at the interface. An experiment of a sudden dam break having water reservoir and L-shape open channel is simulated and compared with the calculated result, which supports the validity of the present model. The model is also applied to calculation of the flow field of APR-1400. The calculated flow field can be characterized by the propagation of waves generated by surface level difference and by the reflection of waves from solid wall. The transient flow rates entering to the Holdup Volume Tank (HVT) can be predicted within a practical limit of computational resource.

Flow and Heat Transfer Simulation in a Complete PWR Fuel Assembly Using Wall-Modelled Rans

2021 ◽  
Author(s):  
Blaž Mikuž ◽  
Ferry Roelofs
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Field ◽  
Fuel Assembly ◽  
Hot Spots ◽  
Complex Geometry ◽  
Computational Domain ◽  
Pressurized Water ◽  
Flow And Heat Transfer ◽  
Significant Difference

Abstract Reproduction of turbulent flow and heat transfer inside a pressurized water reactor (PWR) fuel assembly is a challenging task due to the complex geometry and the huge computational domain. Capability of a wall-modelled RANS approach has been examined, which had already been validated against the measurements of the MATiS-H experiment. The method is here expanded to a larger computational domain aiming to reproduce flow and thermal field in the entire PWR fuel assembly. Namely, in the first part of the present study, wall-modelled RANS is performed in a relatively short section of the representative PWR fuel assembly containing one single mixing grid with an array of 15×15 fuel rods. Linear and nonlinear eddy-viscosity turbulence models have been applied, however no significant difference is observed in the predicted pressure drop in the fuel assembly. The obtained predictions revealed an interesting pattern of swirl flow as well as diagonal cross flow downstream the mixing grid, which is driven by the applied design of split-type mixing vanes. In the second part, the computational model is extended to a domain representative of a complete PWR fuel assembly with ten mixing grids, inlet and outlet sections. Pressure drop and flow field are analysed together with the predicted temperature and potential hot spots. In spite of a relatively coarse spatial resolution of the applied approach, the wall-modelled RANS provided promising results at least for the qualitative prediction of the pressure, flow field and location of hot spots.

Effects of Initial Pressure and Length of a Broken Pipe on the Transient Hydraulic Loads Acting on Nuclear Steam Generator Tubes and Supports During Blowdown Following a Sudden Feedwater Pipe Break

2019 ◽  
Author(s):  
Jong Chull Jo ◽  
Jae-Jun Jeong ◽  
Byong-Jo Yun
Keyword(s):  
Flow Field ◽  
Steam Generator ◽  
Field Data ◽  
Transient Flow ◽  
Initial Pressure ◽  
Pressurized Water Reactor ◽  
Pipe Length ◽  
Pressurized Water ◽  
Steam Generator Tubes ◽  
Transient Flow Fields

Abstract This paper investigates the effects of steam generator initial pressure and length of a broken feedwater pipe on the transient hydraulic loads on the pressurized water reactor (PWR) steam generator (SG) tubes and supports during blowdown following a sudden feedwater line break (FWLB). To do this, the transient flow fields inside the SG and the connected broken feedwater pipe are calculated by realistically treating the discharge flow as the sub-cooled water flashing flow. Then, the calculated transient flow field data are used to predict the transient hydraulic loads on the PWR SG tubes and supports for some specified cases where the SG initial pressure or the broken feedwater pipe length are different from each other.

Comparison of DSMC and CFD Models of Heat Transfer in a Rarefied Two-Dimensional Geometry

2018 ◽  
Author(s):  
Dilesh Maharjan ◽  
Mustafa Hadj-Nacer ◽  
Miles Greiner ◽  
Stefan K. Stefanov
Keyword(s):  
Heat Transfer ◽  
Rarefied Gas ◽  
Complex Geometry ◽  
Direct Simulation Monte Carlo ◽  
Accurate Method ◽  
Vacuum Drying ◽  
Helium Pressure ◽  
Two Dimensional ◽  
Dsmc Method ◽  
Cfd Simulations

During vacuum drying of used nuclear fuel (UNF) canisters, helium pressure is reduced to as low as 67 Pa to promote evaporation and removal of remaining water after draining process. At such low pressure, and considering the dimensions of the system, helium is mildly rarefied, which induces a thermal-resistance temperature-jump at gas–solid interfaces that contributes to the increase of cladding temperature. It is important to maintain the temperature of the cladding below roughly 400 °C to avoid radial hydride formation, which may cause cladding embrittlement during transportation and long-term storage. Direct Simulation Monte Carlo (DSMC) method is an accurate method to predict heat transfer and temperature under rarefied condition. However, it is not convenient for complex geometry like a UNF canister. Computational Fluid Dynamics (CFD) simulations are more convenient to apply but their accuracy for rarefied condition are not well established. This work seeks to validate the use of CFD simulations to model heat transfer through rarefied gas in simple two-dimensional geometry by comparing the results to the more accurate DSMC method. The geometry consists of a circular fuel rod centered inside a square cross-section enclosure filled with rarefied helium. The validated CFD model will be used later to accurately estimate the temperature of an UNF canister subjected to vacuum drying condition.

scholarly journals Influence of a Standing Wave Flow-Field on the Dynamics of a Spray Diffusion Flame

Fluids ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 27
Author(s):  
J. Barry Greenberg ◽  
David Katoshevski
Keyword(s):  
Liquid Phase ◽  
Flow Field ◽  
Standing Wave ◽  
Diffusion Flame ◽  
Stokes Number ◽  
Flame Height ◽  
Wave Flow ◽  
Two Dimensional ◽  
Governing Equations ◽  
First Time

A theoretical investigation of the influence of a standing wave flow-field on the dynamics of a laminar two-dimensional spray diffusion flame is presented for the first time. The mathematical analysis permits mild slip between the droplets and their host surroundings. For the liquid phase, the use of a small Stokes number as the perturbation parameater enables a solution of the governing equations to be developed. Influence of the standing wave flow-field on droplet grouping is described by a specially constructed modification of the vaporization Damkohler number. Instantaneous flame front shapes are found via a solution for the usual Schwab–Zeldovitch parameter. Numerical results obtained from the analytical solution uncover the strong bearing that droplet grouping, induced by the standing wave flow-field, can have on flame height, shape, and type (over- or under-ventilated) and on the existence of multiple flame fronts.

scholarly journals Two-dimensional flow field distribution characteristics of flocking drainage pipes in tunnel

Open Physics ◽  
2020 ◽  
Vol 18 (1) ◽  
pp. 139-148
Author(s):  
Shiyang Liu ◽  
Xuefu Zhang ◽  
Feng Gao ◽  
Liangwen Wei ◽  
Qiang Liu ◽  
...  
Keyword(s):  
Flow Field ◽  
Field Distribution ◽  
Rapid Development ◽  
Maximum Velocity ◽  
Distribution Characteristics ◽  
Two Dimensional ◽  
Dimensional Flow ◽  
Laboratory Test Results ◽  
Transverse Distance ◽  
Two Dimensional Flow

AbstractWith the rapid development of traffic infrastructure in China, the problem of crystal plugging of tunnel drainage pipes becomes increasingly salient. In order to build a mechanism that is resilient to the crystal plugging of flocking drainage pipes, the present study used the numerical simulation to analyze the two-dimensional flow field distribution characteristics of flocking drainage pipes under different flocking spacings. Then, the results were compared with the laboratory test results. According to the results, the maximum velocity distribution in the flow field of flocking drainage pipes is closely related to the transverse distance h of the fluff, while the longitudinal distance h of the fluff causes little effect; when the transverse distance h of the fluff is less than 6.25D (D refers to the diameter of the fluff), the velocity between the adjacent transverse fluffs will be increased by more than 10%. Moreover, the velocity of the upstream and downstream fluffs will be decreased by 90% compared with that of the inlet; the crystal distribution can be more obvious in the place with larger velocity while it is less at the lower flow rate. The results can provide theoretical support for building a mechanism to deal with and remove the crystallization of flocking drainage pipes.

A new dynamic mesh algorithm for studying the 3D transient flow field of tilting pad journal bearings

2016 ◽  
Vol 230 (12) ◽  
pp. 1470-1482 ◽  
Author(s):  
Mengxuan Li ◽  
Chaohua Gu ◽  
Xiaohong Pan ◽  
Shuiying Zheng ◽  
Qiang Li
Keyword(s):  
Flow Field ◽  
Equilibrium Position ◽  
Transient Flow ◽  
Journal Bearings ◽  
Dynamic Mesh ◽  
Static Equilibrium ◽  
Time Step ◽  
Tilting Pad ◽  
Grid Nodes ◽  
Tilting Pad Journal Bearings

A new dynamic mesh algorithm is developed in this paper to realize the three-dimensional (3D) computational fluid dynamics (CFD) method for studying the small clearance transient flow field of tilting pad journal bearings (TPJBs). It is based on a structured grid, ensuring that the total number and the topology relationship of the grid nodes remain unchanged during the dynamic mesh updating process. The displacements of the grid nodes can be precisely recalculated at every time step. The updated mesh maintains high quality and is suitable for transient calculation of large journal displacement in FLUENT. The calculation results, such as the static equilibrium position and the dynamic characteristic coefficients, are consistent with the two-dimensional (2D) solution of the Reynolds equation. Furthermore, in the process of transient analysis, under conditions in which the journal is away from the static equilibrium position, evident differences appear between linearized and transient oil film forces, indicating that the nonlinear transient calculation is more suitable for studying the rotor-bearing system.

Flow Visualization by Means of Contactless Inductive Flow Tomography in the Presence of a Magnetic Brake

2015 ◽  
Vol 15 (1) ◽  
pp. 41-48 ◽  
Author(s):  
Matthias Ratajczak ◽  
Thomas Wondrak ◽  
Klaus Timmel ◽  
Frank Stefani ◽  
Sven Eckert
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Magnetic Fields ◽  
Flow Field ◽  
Continuous Casting ◽  
Flow Structure ◽  
Cross Section ◽  
Two Dimensional ◽  
Slab Casting ◽  
Two Dimensional Flow

AbstractIn continuous casting DC magnetic fields perpendicular to the wide faces of the mold are used to control the flow in the mold. Especially in this case, even a rough knowledge of the flow structure in the mold would be highly desirable. The contactless inductive flow tomography (CIFT) allows to reconstruct the dominating two-dimensional flow structure in a slab casting mold by applying one external magnetic field and by measuring the flow-induced magnetic fields outside the mold. For a physical model of a mold with a cross section of 140 mm×35 mm we present preliminary measurements of the flow field in the mold in the presence of a magnetic brake. In addition, we show first reconstructions of the flow field in a mold with the cross section of 400 mm×100 mm demonstrating the upward scalability of CIFT.

3D Simulation of a Peripheral Adapter J-Groove Attachment Weld in a Vessel Head

2014 ◽  
Author(s):  
Philippe Mourgue ◽  
Vincent Robin ◽  
Philippe Gilles ◽  
Florence Gommez ◽  
Alexandre Brosse ◽  
...  
Keyword(s):  
Complex Geometry ◽  
3D Simulation ◽  
Welding Parameters ◽  
Manufacturing Processes ◽  
Pressurized Water ◽  
Control Rod ◽  
Sequence Modeling ◽  
Component Design ◽  
Water Reactors ◽  
Welding Processes

In Pressurized Water Reactors, most of heavy components and pipes have a large thickness and their manufacturing processes often require multi-pass welding. Despite the stiffness of these components, the distortion issue may be important for operational requirements (e.g. misalignment) or controllability reasons (Non Destructive Examinations have to be achievable, therefore ovalization should be limited). These requirements may be difficult to achieve by simply adjusting welding processes. Indeed because of the complexity of mechanisms involved during a welding operation and the high number of influencing parameters, this process is still essentially based on the experience of the welder. Furthermore the experimental estimation of the stress and distortion level in the component remains a difficult task that is subject to errors even if techniques are currently improved to become more accurate. These are the reasons why AREVA has put a large effort to improve welding numerical simulations, in order to have a better understanding of the involved physical phenomena and also to predict the residual state through the structure. Computational welding mechanics is used to qualify the manufacturing processes in the very early phase of the welded component design. Within the framework of a R&D program whose main objective was to improve tools for the numerical simulation of welding regarding industrial needs, AREVA has decided to validate new methodologies based on 3D computation by comparison with measurements. For this validation task the chosen industrial demonstrator was a Control Rod Drive Mechanism (CRDM) Nozzle with a J-groove attachment weld to the vessel head. For such an application, operations of post-joining straightening have to be limited, if not prohibited, because of their cost or the impossibility to use them in front of a steel giant. The control of distortion during welding operations is a key issue for which simulation can be of great help. Regarding distortion issues, both accurate metal deposit sequence modeling and respect of the real welding parameters are mandatory, especially for multi-pass operation on such a complex geometry. The aim of this paper is to present the simulation of the distortion of a peripheral adapter J-groove attachment weld mock-up. This new full 3D simulation improves the result of the previous one based on lumped pass deposits. It is the result of a fruitful collaboration between AREVA and ESI-Group.

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