CFD-based Evaluation of Interfacial Flows

We investigate experimentally the unsteady draining flow from a rotating tank. The fluid in the tank is first set in solid rotation, before the draining hole is opened. We show that the draining may be drastically reduced by the rotation, as the vortex circulation increases together with the surface deformation. We demonstrate that the usual Torricelli's draining law has to be modified with the surface deformation and that the draining time is mainly governed by a nondimensional parameter corresponding to the ratio of the size of the outlet to the thickness of the Ekman boundary layer.

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“…3(c)], h(r, t ) can no longer be measured with confidence. This phenomenon of bubble entrainment is well known in the literature [41,42].…”

Section: Draining Model From Surface Deformationmentioning

confidence: 65%

Bathtub vortex effect on Torricelli's law

et al. 2023

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“…To see the validity of the CFD-based GE evaluation method, the GC lengths were evaluated and compared to several experimental data, and the evaluated values agreed roughly with the experimental data. In addition, the CFD-based GE evaluation method provided the onset condition of the GE in the 1/1.8 scale partial model of JSFR (5) , which corresponds to that in the test data (6) . Namely, the CFD-based GE evaluation was conducted under two conditions; one is the GE condition under which the GE occurs in the experiment and the other is the non-GE condition under which no GE is observed in the experiment.…”

Section: Basic Conceptsmentioning

confidence: 99%

Study on Turbulent Modeling in Gas Entrainment Evaluation Method

Ito

Ohshima

Nakamine

et al. 2012

JPES

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Suppression of gas entrainment (GE) phenomena caused by free surface vortices are very important to establish an economically superior design of the sodium-cooled fast reactor in Japan (JSFR). However, due to the non-linearity and/or locality of the GE phenomena, it is not easy to evaluate the occurrences of the GE phenomena accurately. In other words, the onset condition of the GE phenomena in the JSFR is not predicted easily based on scaled-model and/or partial-model experiments. Therefore, the authors are developing a CFD-based evaluation method in which the non-linearity and locality of the GE phenomena can be considered. In the evaluation method, macroscopic vortex parameters, e.g. circulation, are determined by three-dimensional CFD and then, GE-related parameters, e.g. gas core (GC) length, are calculated by using the Burgers vortex model. This procedure is efficient to evaluate the GE phenomena in the JSFR. However, it is well known that the Burgers vortex model tends to overestimate the GC length due to the lack of considerations on some physical mechanisms. Therefore, in this study, the authors develop a turbulent vortex model to evaluate the GE phenomena more accurately. Then, the improved GE evaluation method with the turbulent viscosity model is validated by analyzing the GC lengths observed in a simple experiment. The evaluation results show that the GC lengths analyzed by the improved method are shorter in comparison to the original method, and give better agreement with the experimental data.

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“…. In addition, the authors are developing a high-precision CFD code for gas-liquid two-phase flows to evaluate the GE in JSFR quantitatively (Ito et al, 2010 andIto et al, 2013). This CFD code employs the piecewise linear interface calculation (PLIC) algorithm (a high-precision volume-of-fluid algorithm) (Youngs, 1982 andParker andYoungs, 1992) to simulate interfacial dynamic behaviors accurately.…”

Section: Introductionmentioning

confidence: 99%

Physics-basis simulation of bubble pinch-off

Ito

Koizumi

Ohshima

et al. 2016

Mechanical Engineering Journal

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In the last two decades, CFD codes have been widely used for the design studies of NPPs. Recently high-precision simulation models have been developed to evaluate complicated phenomena, e.g. fuel melting in severe accident. The authors also are developing a high-precision CFD code with an interface tracking method to simulate the gas entrainment (GE) phenomena in sodium-cooled fast reactors (SFRs), which might be caused by a highly-intensified free surface vortex. The GE in SFRs is characterized by an elongated interfacial dent along the vortex core and the bubble pinch-off at the tip of the dent. To simulate this complicated phenomenon, the authors' CFD code has physics-basis algorithms which model accurately the interfacial dynamic behavior, the pressure jump condition at an interface and the surface tension. Several verification problems, e.g. the slotted-disk problem, have been already solved and the accuracy of each individual algorithm is confirmed. In this paper, a basic experiment of the GE is simulated to validate the developed CFD code. In the experiment, the entrained gas flow rate is measured by image processing with a high-speed video camera. The simulation result of the entrained flow rate shows comparable value to the experimental data, that is, our CFD code is considered applicable to the evaluation of the GE in SFRs.

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CFD-based Evaluation of Interfacial Flows

Cited by 7 publications

References 27 publications

Bathtub vortex effect on Torricelli's law

Bathtub vortex effect on Torricelli's law

Study on Turbulent Modeling in Gas Entrainment Evaluation Method

Physics-basis simulation of bubble pinch-off

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