Comparison and Uncertainty Quantification of Two-Fluid Models forBubbly Flows with NEPTUNE_CFD and STAR-CCM+

International audienceThe nuclear industry is interested in better understanding the behavior of turbulent boiling flowsand in using modern computational tools for the design and analysis of advanced fuels and reactorsand for simulation and study of mitigation strategies in accident scenarios. Such interests serve asdrivers for the advancement of the 3-dimensional multiphase Computational Fluid Dynamicsapproach. A pair of parallel efforts have been underway in Europe and in the United States, theNEPTUNE and CASL programs respectively, that aim at delivering advanced simulation tools thatwill enable improved safety and economy of operations of the reactor fleet. Results from acollaboration between these two efforts, aimed at advancing the understanding of multiphaseclosures for pressurized water reactor (PWR) application, are presented. Particular attention is paidto the assessment and analysis of the different physical models implemented in NEPTUNE_CFDand STAR-CCM+ codes used in the NEPTUNE and the CASL programs respectively, forapplication to turbulent two-phase bubbly flows. The experiments conducted by Liu and Bankoff(Liu, 1989; Liu and Bankoff 1993a and b) are selected for benchmarking, and predictions from thetwo codes are presented for a broad range of flow conditions and with void fractions varyingbetween 0 and 50percent. Comparison of the CFD simulations and experimental measurements revealsthat a similar level of accuracy is achieved in the two codes. The differences in both sets of closuremodels are analyzed, and their capability to capture the main features of the flow over a wide rangeof experimental conditions are discussed. This analysis paves the way for future improvements ofexisting two-fluid models. The benchmarks are further leveraged for a systematic study of thepropagation of model uncertainties. This provides insights into mechanisms that lead to complexinteractions between individual closures (of the different phenomena) in the multiphase CFDapproach. As such, it is seen that the multi-CFD-code approach and the principled uncertaintyquantification approach are both of great value in assessing the limitations and the level of maturityof multiphase hydrodynamic closures

Cfd study of the transverse migration of bubbles in a narrow rectangular duct assessment of the neptune_cfd code and benchmark of various closure models

International audienceThis paper presents a computational fluid dynamics study of two-phase bubbly flow, and aims ata proper description of the spatial distribution of bubbles observed in narrow rectangular ductsfor various non-uniform inlet conditions. As such the study relies on the air-water experimentsperformed by Liu et al. (2012), and a comparison to their results allows an assessment of theaccuracy of different closure models, such as lift force, wall force and turbulent dispersion.Different interfacial area concentration models are also compared and appraised. The numericalcomputations are performed with the NEPTUNE_CFD code, developed together by AREVA,CEA, EDF and IRSN, and dedicated to the simulation of multiphase flows by means of anEulerian multi-fluid approach

DESIGN POWER SUPPLY CONSIDERATIONS TO COMPENSATE BOOSTER POWER SUPPLIES EFFECTS ON THE SOLEIL STORAGE RING

Abstract The booster power supplies influence the storage ring beam position in synchrotron SOLEIL.To compensate these disturbances, a dedicated wire loop fed by an inhouse developed power supply (PS) was installed in the booster cable tray. The power supply output current is driven by direct measurement of the 3Hz booster power supplies. This paper discusses the PS requirements according to beam position measurements and the original design. Finally the orbit stability improvements when this power supply is switched on are presented

Statistical characterization and modeling of drain current local and global variability in 14 nm bulk FinFETs

session 3: variability characterizationInternational audienceA detailed statistical characterization and modeling of drain current local and global variability in 14nm Si bulk FinFET devices is performed. To this end, an analytical mismatch model covering weak to strong inversion region is used to extract the main matching parameters. Our results show that, despite their very aggressive dimensions in terms of Fin width and height, such devices exhibit excellent local and global variability performance. Moreover, a Lambert-W function-based MOSFET compact model is used for MC simulation of local variability

Design and Operation of CMOS-Compatible Electron Pumps Fabricated With Optical Lithography

International audienc