Experimental study of liquid spreading and atomization due to jet impingement in liquid-liquid systems

Yamamura, Sota*; Fujiwara, Kota*; Honda, Kota*; Yoshida, Hiroyuki; Horiguchi, Naoki; Kaneko, Akiko*; Abe, Yutaka*

Physics of Fluids, 34(8), p.082110_1 - 082110_13, 2022/08

https://doi.org/10.1063/5.0100340

Liquid spreading and atomization due to jet impingement in liquid-liquid systems are considered to be crucial for understanding the cooling behavior of high-temperature molten material in a shallow water pool. This phenomenon takes place when a liquid jet enters a pool filled with other immiscible liquid. The jet spreads radially after impinging on the floor while forming a thin liquid film and atomizing droplets. In this paper, we explain the result to quantify the unsteady three-dimensional behavior of the spreading jet by the employment of 3D-LIF measurements and 3-dimensional reconstruction. Under high flow velocity conditions, the phenomena of hydraulic jump and atomization of the liquid film occurred along with the spreading. To evaluate the spreading behavior, a comparison of the jump radius position of the liquid-liquid system as the representative value was made with the one calculated by the existing theory of a gas-liquid system. As the result, the spreading of the liquid film in the liquid-liquid system was suppressed compared with that in the gas-liquid system. Furthermore, the PTV method was successfully used to measure the velocity boundary layer and velocity profile in the liquid film, which are important factors that affect the spreading mechanism of the liquid film. These results revealed that in liquid-liquid systems, shear stress at the liquid-liquid interface causes a decrease in the flow velocity and suppressed the development of the velocity boundary layer. Also, to evaluate the atomization behavior, the number and diameter distribution of the droplets were measured from the acquired 3-dimensional shape data of the jet. As the result, the number of droplets increased with the flow velocity. Based on these results, we concluded that the spreading of the liquid film is affected by such atomization behavior.

Identification of carbon in glassy cesium-bearing microparticles using electron microscopy and formation mechanisms of the microparticles

Hidaka, Akihide

Nuclear Technology, 208(2), p.318 - 334, 2022/02

https://doi.org/10.1080/00295450.2021.1929767

The author previously proposed that the Cs bearing microparticle (Type A) may have been formed by melting and atomization of glass fibers (GF) of the HEPA filter in the SGTS due to flame and blast during the hydrogen explosion in Unit 3. If this hypothesis is correct, the Type A could contain or accompany carbon (C), that ignites spontaneously above 623 K, because of the limited time to be heated up, inclusion of C in the binder applied on the GF surface and closely located charcoal filter. As the previous studies did not focus on C, the present analyses were performed with EPMA whether the Type A contains C. The results showed that the Type A contained C originating from the binder, and non-spherical particles accompanied by the Type A and the film surrounding the Type A contained more C, which is thought to originate from the charcoal filter. These results cannot be explained by the other mechanisms proposed so far, and can be explained consistently by the author proposed hypothesis.

Research on the fundamental process of thermal-hydraulic behaviors in severe accident; Estimation of trigger condition for vapor explosion, JAERI's nuclear research promotion program, H10-027-1 (Contract research)

Nariai, Hideki*

JAERI-Tech 2002-009, 60 Pages, 2002/03

JAERI-Tech-2002-009.pdf:7.73MB

no abstracts in English

Effects of agitation in a shallow pool on atomization behavior of a jet

Masaki, Naoto*; Kaneko, Akiko*; Horiguchi, Naoki; Yoshida, Hiroyuki

no journal, , 

During a severe accident in nuclear reactors, melted fuel rods and other materials may fall as liquid jets into the pool of cooling water remaining in the lower head of the pressure vessel. From the viewpoint of preventing accident development, the clarification of cooling and solidification mechanisms with atomization in the cooling water is essential. Many researchers performed experimental and analytical work to understand jet behavior and atomization in a deep pool. In the case of insufficient water depth, i.e., shallow water pool, there are a few reports in both experimental and analytical approaches. The reports of shallow pools show that atomization occurs even after the jet has impacted the bottom wall. However, the mechanism has not been understood. In this study, we assumed that instability due to velocity difference affects the atomization in a shallow-water pool and tried to give a velocity difference to the interface as an agitation using a vortex provided by a stirrer to examine whether the agitation affects atomization. We conducted visualization and measurement experiments using a simulated liquid-liquid two-fluid system in the shallow pool. As a result, an agitation using a vortex occurred in the pool. The number of droplets and the rise time of the number changed increasing the stirrer frequency. This result suggests that the agitation contributed to the atomization.