Simulation of a jet flow rectified by a grating-type structure using immersed boundary methods

グレーチング構造がジェット流れに及ぼす整流作用についての境界埋め込み法による評価

廣瀬 意育  ; 安部 諭  ; 石垣 将宏* ; 柴本 泰照 ; 日引 俊*

Hirose, Yoshiyasu; Abe, Satoshi; Ishigaki, Masahiro*; Shibamoto, Yasuteru; Hibiki, Takashi*

Immersed boundary methods (IBMs) have been developed as complementary methods for computational fluid dynamics (CFD). They allow a flow simulation in a mock-up model that includes complex-shaped inner structures and/or boundaries with a non-body conformal mesh. Such a model might force us to create a complicated body-fitted mesh with a high cost in the conventional CFD (CCFD) approach. We focus on the Brinkman penalization (BP) method and its extended version, which we call here the extended Brinkman penalization method (EBP), among the different types of IBMs, aiming to apply them to the phenomena that occur during severe accidents in a nuclear reactor containment vessel and explore the possibility that the methods can partially replace the CCFD. In this paper, as a preliminary step to validate the applicability of these methods, we measure the jet flow rectified by a grating-type structure used for the validation of numerical techniques and apply them to simulate the behavior of an upward jet rectified by a horizontally placed grating-type structure modeled as an immersed body. This type of structure is generally used in reactor buildings, and it is crucial to evaluate their influence on gaseous flows because the behaviors of hydrogen produced during severe accidents may be influenced by them. The structure is selected as our subject because it has moderate complexity, enabling us to examine the effects of the IBMs and compare them with CCFD. We investigate whether these methods can reproduce a result of corresponding CCFD in which the grating is modeled as body-conformal mesh and show that the former can produce the latter with equivalent accuracy. All these results are also compared with the experimental data on the flow velocity distributions downstream of the grating measured using particle image velocimetry.