Numerical Simulation of Jet Issuing Diagonally Upward into Density-Stratified Fluid in Cylindrical Tank

Tomohiro Degawa,Isao Aozasa,Tomomi Uchiyama,Akira Ishikawa,Koji Motoyama

doi:10.4236/jpee.2018.63004

Tomohiro Degawa, Isao Aozasa + Show 3 more

Open Access

https://doi.org/10.4236/jpee.2018.63004

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Abstract

This study simulates the behavior of a jet issuing into a two-layer density-stratified fluid in a cylindrical tank and the resulting mixing phenomena. The upper and lower fluids are water and an aqueous solution of sodium chloride (NaCl), respectively, with the lower fluid issuing diagonally upward from a nozzle on the bottom of the tank. The angle between the centerline of the jet and the tank bottom is 60°. The phenomena when the Reynolds number Re of the jet is 475, 1426, and 2614 are simulated. The mass concentration of the aqueous solution of NaCl is 0.02. The simulation successfully grasps the jet behavior and the resulting mixing, which agree with the authors’ experimental results at the corresponding Re value. The secondary flows that appear in the horizontal cross-sections consist of a pair of vortices and flows along the tank wall. The secondary flow at the density interface represents the intrusion of an internal density current, which gives rise to mixing along the interface.

Highlights

To efficiently store liquefied natural gas (LNG), many kinds of LNG from different production areas are stored in the same LNG tank
As the density of LNG is specific to the production area, density stratification sometimes occurs when one batch of LNG is loaded on top of another batch of LNG in the same storage tank
The authors [7] conducted an experimental study of the behavior of the jet and the resulting mixing phenomena under the same conditions as those in the present simulation. They revealed that the jet behavior relative to the density interface can be classified into three patterns (Pattern A, Pattern B, and Pattern C) according to the value of Re

Summary

Introduction

To efficiently store liquefied natural gas (LNG), many kinds of LNG from different production areas are stored in the same LNG tank. As the density of LNG is specific to the production area, density stratification sometimes occurs when one batch of LNG is loaded on top of another batch of LNG in the same storage tank. When the density of the lower LNG layer becomes lower than that of the upper layer, sudden mixing, known as rollover, occurs. Rollover generates large amounts of vaporized gases, which cause severe damage to the storage tank due to over pressurization. The prevention and elimination of LNG stratification is essential for the operation of LNG storage tanks

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