CFD Analysis of Turbulent Flow in a Nuclear Fuel Bundle With Mixing Vane

2002 ◽  
Author(s):  
Wang Kee In ◽  
Dong Seok Oh ◽  
Tae Hyun Chun
Keyword(s):  
Turbulent Flow ◽  
Nuclear Fuel ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Cfd Analysis ◽  
Mean Flow ◽  
Cfd Models ◽  
Fuel Bundle ◽  
Rod Array

A computational fluid dynamics (CFD) analysis was performed to investigate the coolant mixing in a nuclear fuel bundle that is promoted by the mixing vane on the grid spacer. Single and multiple subchannels of one grid span of the fuel bundle were modeled to simulate a 5×5 rod array experiment with the mixing vane. The three-dimensional CFD models were generated by a structured multi-block method. The standard k-ε turbulence model was used in the current CFD simulation since it is practically useful and converges well for the complex turbulent flow in a nuclear fuel bundle. The CFD predictions of axial and lateral mean flow velocities showed a somewhat large difference from the experimental results near the spacer but represented the overall characteristics of coolant mixing well in a nuclear fuel bundle with the mixing vane. Comparison of single and multiple subchannel predictions shows good agreement of the flow characteristics in the central subchannel of the rod array. The simulation of multiple subchannels shows a slightly off-centered swirl in the peripheral subchannels due to the external wall of the rod array. It also shows no significant swirl and crossflow in the wall subchannels and the corner subchannels.

Developed a Spacer Grid for the Future PWR Fuel Assembly by Considering the Thermal/Hydraulic and Mechanical/Structural Performance

2004 ◽  
Author(s):  
Kyung-Ho Yoon ◽  
Wang-Kee In ◽  
Heung-Seok Kang ◽  
Kee-Nam Song
Keyword(s):  
Fuel Assembly ◽  
Nuclear Fuel ◽  
Cfd Simulation ◽  
Fe Model ◽  
Mean Flow ◽  
Fe Method ◽  
Spacer Grid ◽  
Fuel Bundle ◽  
Rod Array ◽  
The Impact

The spacer grid is one of the structural components for the fuel assembly. In order to increase or extend the fuel life cycle, a spacer grid which has a much higher performance from the thermal/hydraulic and mechanical/structural point of view will be needed. From the thermal/hydraulic viewpoint, the CHF margin is very important in order to extend its life. Particularly, the mixing flow or cross flow between the subchannels have to be reinforced for this purpose. From the mechanical/structural viewpoint, the critical strength and the fuel rod support behaviour of a spacer grid are the same as the TH performance improvement for the next generation fuel. A computational fluid dynamics (CFD) analysis was performed to investigate the coolant mixing in a nuclear fuel bundle that is promoted by the mixing vane on the grid spacer. Single and multiple subchannels of one grid span of the fuel bundle were modeled to simulate a 5by5 rod array experiment with the mixing vane. The three-dimensional CFD models were generated by a structured multi-block method. The standard k-ε turbulence model was used in the current CFD simulation since it is practically useful and converges well for the complex turbulent flow in a nuclear fuel bundle. The CFD predictions of the axial and lateral mean flow velocities showed a somewhat larger difference from the experimental results near the spacer but represented the overall characteristics of the coolant mixing well in a nuclear fuel bundle with the mixing vane. Comparison of the single and multiple subchannel predictions shows a good agreement for the flow characteristics in the central subchannel of the rod array. The simulation of the multiple subchannels shows a slightly off-centered swirl in the peripheral subchannels due to the external wall of the rod array. It also shows no significant swirl and crossflow in the wall subchannels and the corner subchannels. In addition to this, the impact and the stress analysis of a spacer grid are accomplished by the FE method. The FE model was created using I-DEAS [4], and the ABAQUS/explicit version 6.3 commercial code was used for the solver. The FE analysis procedure was established, the FE analyses results were verified by the experimental method. The developed spacer grid will be evaluated from the thermal/hydraulic and mechanical/structural design criteria.

Numerical Prediction of Flow in a Nuclear Fuel Bundle With Various Turbulence Models

2002 ◽  
Author(s):  
Wang Kee In ◽  
Dong Seok Oh ◽  
Tae Hyun Chun
Keyword(s):  
Turbulent Flow ◽  
Nuclear Fuel ◽  
Turbulence Models ◽  
Convective Transport ◽  
Stress Model ◽  
Convergence Criteria ◽  
Mean Flow ◽  
Numerical Predictions ◽  
Viscosity Models ◽  
Fuel Bundle

The numerical predictions using the standard and RNG k–ε eddy viscosity models, differential stress model (DSM) and algebraic stress model (ASM) are examined for the turbulent flow in a nuclear fuel bundle with the mixing vane. The hybrid (first-order) and curvature-compensated convective transport (CCCT) schemes were used to examine the effect of the differencing scheme for the convection term. The CCCT scheme was found to more accurately predict the characteristics of turbulent flow in the fuel bundle. There is a negligible difference in the prediction performance between the standard and RNG k-ε models. The calculation using ASM failed in meeting the convergence criteria. DSM appeared to more accurately predict the mean flow velocities as well as the turbulence parameters.

Numerical Simulation of Flow Through Nuclear Fuel Bundles With Angular Misalignments

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
A. Bhattacharya ◽  
S. D. Yu
Keyword(s):  
Nuclear Fuel ◽  
Large Scale ◽  
Computational Models ◽  
Three Dimensional ◽  
Cross Flow ◽  
Eddy Simulation ◽  
Cfd Models ◽  
Fuel Bundle ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through

Comprehensive computational fluid dynamics (CFD) models are developed and analyzed in this paper to study the three-dimensional flow through simulated nuclear fuel bundles with angular misalignments inside a pressure tube. The large eddy simulation (LES) scheme is employed to solve the large scale complex computational models with an aim to understanding the effects of the bundle-to-bundle angular misalignments on unsteady flow and flow-induced excitations on the fuel bundle structures. The proposed numerical scheme is validated with both numerical and experimental work available in the literature. Numerical results obtained from the current computational models indicate the presence of significant lateral or cross-flow in the bundle-to-bundle interface region for bundles with angular misalignments. The mean and the rms values of the lateral fluid excitations on the first bundle are found to be sensitive with respect to the change in angular misalignments between bundles.

scholarly journals Interactions between Tandem Cylinders in an Open Channel: Impact on Mean and Turbulent Flow Characteristics

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1718
Author(s):  
Hasan Zobeyer ◽  
Abul B. M. Baki ◽  
Saika Nowshin Nowrin
Keyword(s):  
Turbulent Flow ◽  
Open Channel ◽  
Recirculation Zone ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Recirculation ◽  
Tandem Cylinders ◽  
Flow Development ◽  
The Mean ◽  
Recirculation Length

The flow hydrodynamics around a single cylinder differ significantly from the flow fields around two cylinders in a tandem or side-by-side arrangement. In this study, the experimental results on the mean and turbulence characteristics of flow generated by a pair of cylinders placed in tandem in an open-channel flume are presented. An acoustic Doppler velocimeter (ADV) was used to measure the instantaneous three-dimensional velocity components. This study investigated the effect of cylinder spacing at 3D, 6D, and 9D (center to center) distances on the mean and turbulent flow profiles and the distribution of near-bed shear stress behind the tandem cylinders in the plane of symmetry, where D is the cylinder diameter. The results revealed that the downstream cylinder influenced the flow development between cylinders (i.e., midstream) with 3D, 6D, and 9D spacing. However, the downstream cylinder controlled the flow recirculation length midstream for the 3D distance and showed zero interruption in the 6D and 9D distances. The peak of the turbulent metrics generally occurred near the end of the recirculation zone in all scenarios.

Turbulent flow between counter-rotating concentric cylinders: a direct numerical simulation study

2008 ◽  
Vol 615 ◽  
pp. 371-399 ◽  
Author(s):  
S. DONG
Keyword(s):  
Turbulent Flow ◽  
Large Scale ◽  
Outer Cylinder ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Taylor Vortex ◽  
Small Scale ◽  
Mean Flow ◽  
Concentric Cylinders ◽  
High Reynolds

We report three-dimensional direct numerical simulations of the turbulent flow between counter-rotating concentric cylinders with a radius ratio 0.5. The inner- and outer-cylinder Reynolds numbers have the same magnitude, which ranges from 500 to 4000 in the simulations. We show that with the increase of Reynolds number, the prevailing structures in the flow are azimuthal vortices with scales much smaller than the cylinder gap. At high Reynolds numbers, while the instantaneous small-scale vortices permeate the entire domain, the large-scale Taylor vortex motions manifested by the time-averaged field do not penetrate a layer of fluid near the outer cylinder. Comparisons between the standard Taylor–Couette system (rotating inner cylinder, fixed outer cylinder) and the counter-rotating system demonstrate the profound effects of the Coriolis force on the mean flow and other statistical quantities. The dynamical and statistical features of the flow have been investigated in detail.

Abstract P531: Cerebral Blood Flow Analysis Using Flow Wire Measurements and CFD Analysis

Stroke ◽  
2021 ◽  
Vol 52 (Suppl_1) ◽  
Author(s):  
Aichi Chien ◽  
Huy Dinh ◽  
Viktor Szeder ◽  
Fernando Vinuela
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Flow Velocity ◽  
Cfd Simulation ◽  
Cfd Analysis ◽  
Flow Data ◽  
Velocity Data ◽  
Mean Flow ◽  
Good Agreement ◽  
Cerebral Vascular

Introduction: Clinical reports show that cerebral blood flow conditions are indicative of cerebral vascular disease. While methods for characterizing cerebral vascular flow have been extensively reported in the past, comparative analyses between direct flow measurements (DM) and computational flow dynamic (CFD) analysis remain limited. We hypothesize that flow data can be reliably measured both directly and through CFD in normal vessels. Methods: A left heart replicator was used as a realistic cardiac pump which maintained systolic pressure at 120 mmHg and diastolic pressure at 80 mmHg. A stenotic model with 50% stenosis for the ICA was connected to the replicator. A ComboWire was used for DM and recorded flow pressure and velocity. CFD was used to study flow. Results: In areas at the proximal end of the stenosis, the pressure and flow velocity derived from DM and CFD were in good agreement. At the end of systole and diastole, DM pressure were 145.42 mmHg and 73.53 mmHg, respectively. CFD simulation for the same system obtained the pressure at the end of systole and diastole of 147.16 mmHg and 74.64 mmHg, respectively. The velocity data collected from DM was at 15.40 cm/s and 7.74 cm/s for systolic flow and mean flow velocity. CFD measured flow was 17.85 cm/s and 11.37 cm/s, respectively. In areas at the distal end of the stenosis, pressure data showed good agreement between DM and CFD analysis. The DM were 138 and 70.81 mmHg at the end of systole and diastole, respectively; CFD simulation yielded 145.95 and 74.51 mmHg, respectively. Variations in the velocity data were observed at this location (Fig, pink arrows). Conclusion: DM of pressure showed good agreement with CFD simulation in all areas of the vessel. DM of velocity using the flow wire were highly affected by location of the measurement. CFD analysis can provide more consistent flow data for flow information collection along the vasculature.

Development and Validation of an Ignition Model for SI Engines

2006 ◽  
Author(s):  
Stefania Falfari ◽  
Gian Marco Bianchi
Keyword(s):  
Cfd Simulation ◽  
Combustion Process ◽  
Three Dimensional ◽  
Electrical Energy ◽  
Combustion Model ◽  
Test Case ◽  
Ignition Process ◽  
Mean Flow ◽  
Flame Kernel ◽  
Si Engines

In SI engines the ignition process strongly affects the combustion process. Its accurate modelling becomes a key issue for a design-oriented CFD simulation of the combustion process. Different approaches to simulate ignition have been proposed. The common base is decoupling the physics related to the very first ignition phase when a plasma is formed from that of the development of the flame kernel. The critical point of ignition models is related to the capability of representing the effect of ignition system characteristics, the criterion used for flame deposit and the initialisation of the combustion model. This paper aims to present and validates extensively an ignition model suited for CFD calculation of premixed combustion. The ignition model implemented in a customized version of the Kiva 3 code is coupled with ECFM Flamelet combustion model. The ignition model simulates the plasma/kernel expansion based on a lump evaluation of main ignition processes (i.e., breakdown, arc-phase and glow phase). A double switch criterion based on physical and numerical consideration is used to switch to the main combustion model. The Herweg and Maly experimental test case has been used to check the model capability. In particular, two different ignition systems having different amount of electrical energy released during spark discharge are considered. Comparisons with experimental results allowed testing the model with respect to its capability to reproduce the effects of mixture equivalence ratio, mean flow, turbulence and spark energy on flame kernel development as never done before in three-dimensional RANS CFD combustion modelling of premixed flames.

scholarly journals Flow visualization using momentum and energy transport tubes and applications to turbulent flow in wind farms

2013 ◽  
Vol 715 ◽  
pp. 335-358 ◽  
Author(s):  
Johan Meyers ◽  
Charles Meneveau
Keyword(s):  
Turbulent Flow ◽  
Flow Visualization ◽  
Energy Transport ◽  
Three Dimensional ◽  
Wind Farms ◽  
Mean Flow ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Using Data ◽  
Large Wind

AbstractAs a generalization of the mass–flux based classical stream tube, the concept of momentum and energy transport tubes is discussed as a flow visualization tool. These transport tubes have the property that no fluxes of momentum or energy exist over their respective tube mantles. As an example application using data from large eddy simulation, such tubes are visualized for the mean-flow structure of turbulent flow in large wind farms, in fully developed wind-turbine-array boundary layers. The three-dimensional organization of energy transport tubes changes considerably when turbine spacings are varied, enabling the visualization of the path taken by the kinetic energy flux that is ultimately available at any given turbine within the array.

Experimental and Numerical Investigations of the 3-D Turbulent Flow Characteristics Around Submerged Permeable Breakwaters

2017 ◽  
Author(s):  
Caleb Stanley ◽  
Georgios Etsias ◽  
Steven Dabelow ◽  
Dimitrios Dermisis ◽  
Ning Zhang
Keyword(s):  
Turbulent Flow ◽  
Laboratory Experiments ◽  
Flow Characteristics ◽  
Mean Flow ◽  
Turbulent Structures ◽  
3 Dimensional ◽  
The Mean ◽  
Design Simplicity ◽  
Study Laboratory ◽  
Geometric Designs

Submerged breakwaters are favored for their design simplicity in projects intended to dissipate wave energy and reduce erosion on coastlines. Despite their popularity, the effects that submerged breakwaters exhibit on the surrounding hydrodynamics are not clearly understood, mainly due to the flow complexity generated from 3-dimensional turbulent structures in the vicinity of the breakwaters that affect the mean flow characteristics and the transport of sediment. The objective of this study was to evaluate the effects that various geometric designs of submerged permeable breakwaters have on the turbulent flow characteristics. To meet the objective of this study, laboratory experiments were performed in a water-recirculating flume, in which the 3-dimensional velocity field was recorded in the vicinity of scaled breakwater models. Breakwaters that were tested include non-permeable, three-hole, and ten-hole models. The experimental data obtained was compared to results obtained from numerical simulations. Results demonstrated that permeable breakwaters exhibit more vertical turbulent strength than their non-permeable counterparts. It was also discovered that three-hole breakwater models produce higher turbulent fluctuations than that of the ten-hole breakwaters. The results from this study will be used eventually to enhance the performance of restoration projects in coastal areas in Louisiana.

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