地下空間における高圧ガスの解放に伴う流れ場の数値シミュレーション Ｌ字形のダクト内における衝撃波の数値解析

Abstract

This paper treats a numerical analysis of behaviour of moving shock and contact discontinuities by an explosion of high-pressure gas in an underground space. Two situations are considered as the form of space. One is an abruptly wide-open duct. The other is an L-shaped duct with a sharp corner.First, as soon as a shock front travelling straightforward by a sudden breakdown of diaphragm passes through sharply wide-open space, the shock front diffracts around an acute corner, and thereby a vortical structure is incipiently formed at the downstream region from the corner. The front of diffracted shock wave extends with keeping the self-similarity about a corner edge. Second, in the L-shaped duct, an outside part of the shock front is incident on the opposite wall and reflected from there and an inside part of the shock front diffracts around the corner. As a result, the reflected shock and the diffracted one interact with each other and the shocks with the threefold point are formed. The reflected shock, which does not interact with the diffracted one, interacts with the contact surface almost immovable at a little upstream side from the outside wall. Therefore, the gas near the outer corner remains in a high-pressure and high-temperature state by repeating the reflection as well as the transmission. However, these discontinuity waves become decayed as time goes by. The above-mentioned processes are discussed here from various points of view.