Comparative study on the effect of reactor internal structure geometry modeling methods on the prediction accuracy for PWR internal flow distribution

The objective of this paper is the study and the analysis of the complex phenomena related to the internal flow in a centrifugal fan, using Computational Fluid Dynamics (CFD) tools, completed with experimental investigation in order to validate the used numerical models. The CFD analysis concerns 2D and 3D unsteady flow. The studied phenomena are the interactions and unsteadiness induced by the motion of the rotating blades relatively to the volute and their impact on the aeroacoustic behavior of the fan. Thus, 3D and 2D unsteady calculations using Unsteady Reynolds Averaged Navier Stokes (URANS) approach has been applied on a hybrid mesh grid whose refinement has been studied and adapted to the flow morphology. Turbulence has been modeled with the k-ω-Shear Stress Model (SST) model. The computational domain has been divided into two zones, a rotating zone including the impeller and stationary zone including the volute. A sliding mesh technique has been applied to the interfaces in order to allow the unsteady interactions between the two zones. The overall performances predicted by the computations have been validated at different flow rate. For each geometry modeling (2D and 3D), the unsteady part of the study is illustrated by analyzing the pressure fluctuations on different points from the lateral surface of the volute. The analysis of the wake generated by the rotation of the blower shows that the volute tongue is the main zone of unsteadiness and flow perturbations. In order to predict the acoustic pressures, the unsteady flow field variables provided by the CFD calculations have been used as inputs in the Ffowks Williams-Hawkings equations.

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Numerical Simulation of Three Dimensional Internal Flow of a PWR Reactor

Volume 3: Thermal-Hydraulics ◽

10.1115/icone24-61013 ◽

2016 ◽

Author(s):

Jian Ge ◽

Wenxi Tian ◽

Tingting Xu ◽

Jiesheng Min ◽

Guofei Chen ◽

...

Keyword(s):

Cfd Simulation ◽

Physical Phenomenon ◽

Three Dimensional ◽

Great Influence ◽

Flow Distribution ◽

Internal Flow ◽

Hydraulic Characteristics ◽

Main Research ◽

The Core ◽

Internal Structures

The coolant flow in the reactor pressure vessel (RPV) lower plenum is complex due to the presence of various internal structures, which has a great influence on the flow distribution at the core inlet. In order to study the thermal hydraulic characteristics in the RPV lower plenum, many scaled down test facilities have been built for different PWR reactors such as Juliette, ACOP, and ROCOM. Although the experimental study is still a main research method, it may be not economical in some situations due to the high cost and the long study period. Compared with the experimental method, Computational Fluid Dynamics (CFD) methodology can simulate three dimensional fluid flow in complex geometries and perform parametric studies more easily. The detailed and localized thermal hydraulic characteristics which are difficult to measure during experiments can be obtained. So CFD simulation has been widely used nowadays. One of the purposes of numerical simulations of the internal flow in a RPV is to get the flow distribution at the core inlet, then to make an optimization for the flow diffusor in the RPV lower plenum to improve the core inlet flow distribution homogeneity. Appropriate optimizations for the flow diffusor depends on fully understanding the flow phenomena in the RPV lower plenum. In this paper, Phenomenon Identification and Ranking Table (PIRT) is adopted to analyze the physical phenomenon that occurs in the RPV lower plenum with the typical 900MW reactor internal structures, and the importance of the various physical phenomena and the reference parameters are ranked through expert opinions and literature review. Then a preliminary three dimensional CFD simulation for the reactor vessel is conducted. The main phenomena identified by the PIRT can be observed from the simulation results.

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Populistic Rhetoric: Structures Over Senses

Praktyka Teoretyczna ◽

10.14746/prt2021.4.3 ◽

2021 ◽

Vol 42 (4) ◽

pp. 65-92

Author(s):

Patrycja Pichnicka-Trivedi

Keyword(s):

Structural Analysis ◽

Comparative Study ◽

Internal Structure ◽

Main Tool ◽

Social Conditions ◽

Global World

This article makes a comparative study of American and Polish rightist populisms and their ways of operating using structural analysis of their discourses as a main tool of examination. It aims to prove that those are indeed structural similarities that are responsible for the success of populisms in diverse environments. While examining examples of populist rhetorics and noticing the surprising efficacy of similar discourse in different political and social conditions, I expose internal structure of populism(s). I state that populism(s) is constructed mostly by and on empty signifiers. Those signifiers can then be matched in broader structures, of which the most fundamental one is the opposition: “We”—“Them”. Such mythological structures are flexible enough so that any subject or object can be inscribed into them. They are also flexible enough to transgress the borders of one domain and to transgress state borders: to “wander” around the global world.

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