Study on Steady-State Sound Transmission and Propagation Analysis Using the Two-Dimensional Wave Based Method

著者らは，定常音響構造連成解析において，従来の手法では解析が困難な中間周波数帯を解析可能な決定論的手法である波動ベース法（WBM）に着目し，フェアリング内部の宇宙機の2 次元内部定常音響振動連成解析を行ってきた．本報告では，著者らが開発し拡張した2 次元解析コードを用いて，内部音響透過問題と，解析領域の広い外部音響伝播問題に対するWBM の適用性を検討した結果を示す．音響透過問題に関しては，単純な弾性板を通じた音響透過損失の計算を行い，有限要素法(FEM) による解析結果と比較することによってWBM の解析精度の検証を行った．その際，WBM とFEM の両者に対して，弾性板の端部における不連続な境界条件に付随して解析精度が悪化する問題を指摘し，簡易的な手法で問題を回避する方法を提案した．一方，外部問題においては，ロケット打ち上げ時の射場の定常音響伝播の計算を行い，無限遠において音が反射しないことを保証する放射条件を厳密に満足して，広い解析領域および広い周波数領域における問題を扱うことができることを示した．
Acoustic environment at a launch site is affected by jets from rocket engines, as well as by geometric features of a launch pad. Then, spacecraft are also exposed to acoustic pressure with the wide frequency range transmitted through a payload fairing. In the case that vibro-acoustic response is predicted using steady-state vibroacoustic analysis, there actually exists the mid-frequency range in which there are no mature numerical methods. This report deals with the novel Wave Based Method (WBM), a deterministic approach for steady-state vibroacoustic analysis in the wide frequency range. Then the two-dimensional (2D) WBM code developed by the authors is applied to some sound transmission problems and exterior problems. In the sound transmission analysis, it is found that discontinuous impedance boundary conditions (BCs) must be fi tted by using continuous functions to obtain more accurate results using both WBM and FEM. After smoothing the BCs, numerical prediction results of our sound transmission models by the 2D WBM and FEM are compared, and the 2D WBM are verified. Furthermore, in order to verify the 2D code extended for the exterior problems, it is applied to simple launch pad models. In both propagation and transmission problems, it can be stated that the WBM has quite high potential to be applied in the higher frequency range.
形態: カラー図版あり
Physical characteristics: Original contains color illustrations
資料番号: AA0064697000
レポート番号: JAXA-RR-09-008