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Journal Articles

Numerical simulation of thermal striping phenomena for fundamental validation and uncertainty quantification; Application of least square version GCI and area validation method to impinging jet in a T-Junction piping system

Tanaka, Masaaki

Proceedings of 12th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-12) (USB Flash Drive), 14 Pages, 2018/10

A numerical simulation code MUGTHES has been developed to estimate high cycle thermal fatigue in SFRs. In development of numerical simulation code, verification, validation, and uncertainty quantification (VVUQ) are indispensable. In this study, numerical simulation at impinging jet condition in the WATLON experiment which was the water experiment of a T-junction piping system was performed for the fundamental validation. Based on the previous studies, the simplified least square version GCI method and the area validation metrics were employed as reference methods to quantify uncertainty and to measure the degree of difference between the numerical and the experimental results, respectively. Through the examinations, the potential applicability of the MUGTHES to the thermal striping phenomena was indicated and requirements of modification in the simulation was suggested in accordance with the uncertainty values.

JAEA Reports

Numerical Investigation on Thermal Stratification and Striping Phenomena in Various Coolants

Yang Zumao*;

JNC-TN9400 2000-009, 81 Pages, 2000/02


It is important to study thermal stratification and striping phenomena for they can induce thermal fatigue failure of structures. This presentation uses the AQUA code, which has been developed in Japan Nuclear Cycle Development Institute (JNC), to investigate the characteristics of these thermal phenomena in water, liquid sodium, liquid lead and carbon dioxide gas.There are altogether eight calculated cases with same Richardson number and initial inlet hot velocity in thermal stratification calculations, in which four cases have same velocity difference between inlet hot and cold fluid, the other four cases with same temperature difference. The calculated results show : (1) The fluid's properties and initial conditions have considerable effects on thermal stratification, which is decided by the combination of such as thermal conduction, viscous dissipation and buoyant force, etc., and (2) The gas has distinctive thermal stratification characteristics from those of liquid because for

JAEA Reports

Numerical investigation on thermal striping conditions for a tee junction of LMFBR coolant pipes (IV); Investigation on second-order moments in coolant mixing region

JNC-TN9400 2000-008, 323 Pages, 2000/02


This rport presents numerical results on theemal striping characteristics at a tee junction of LMFBR coolant pipe, carried out using a direct numerical simulation code DINUS-3. In the numerical investigations, it was considered a tee junction system consisted of a main pipe (1.33 cm$$^{I.D.}$$) with a 90$$^{circ}$$ elbow and a branch pipe, and four parameters, j.e., (1)diameter ratio $$alpha$$ between both the pipes, (2)flow velocity ratio $$beta$$ between both the pipes, (3)angle $$gamma$$ between both the pipes, and (4)Reynolds number Re. From the numerical investigations, the following characteristics were obtained: (1)According to the decreasing of the diameter ratio, significant area of second-order moments was expanded in the fixed condition of $$beta$$=1.0. (2)Significant second-order moments area was expanded for the increasing of the flow velocity ratio $$beta$$ specified by varying of the main pipe velocity in the case of a $$alpha$$ = 1.0 constant condition. 0n the other hand, the area was expanded for the decreasing of the velocity ratio $$beta$$ defined by varying of the branch pipe velocity in the case of a $$alpha$$ = 3.0 constant condition. (3)Maximum second-order moments values were generated in the case of $$gamma$$ = 180$$^{circ}$$ due to the influence of interactions between main pipe flows and jet flows from the branch pipe. (4)According to the increase of Reynolds number, significant area of second-order moments was expanded due to the activation of turbulence mixing in the main pipe.

JAEA Reports

Thermal striping an experiental investigation on mixing of jets; Part III Remaining hydrodynamic results from initial experiments

Tokuhiro, Akira; Kimura, Nobuyuki;

JNC-TN9400 2000-014, 86 Pages, 1999/06


Experiments were performed using the WAJECO facility to investigate the thermohydraulic mixing of multiple jets flowing out of a LMFBR core. Mixing is the root of the thermal striping problem. The multiple jets are typically at different velocities and temperatures and may induce thermal stresses upon components they impinge. In our study we modeled the mixing of three vertical jets, the central at a lower temperature than the two adjacent jets at equal temperatures. The jets are quasi-planar. The parameters were the average exit jet velocities (Uo,av) and the temperature difference between the "cold" and "hot" jets ($$Delta$$Thc=Thot-Tcold). Measurements of the liquid velocity, initially using laser Doppler velocimetry (LDV) and later ultrasound Doppler velocimetry (UDV), for both our reference single-jet and the triple-jet configuration, comprised Phase I of the experiments (up to 1994). Two reports (TN9410 96-181 and TN9410 96-296; in Japanese) reported on the hydraulic and heat tra

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