2次元層流境界層の受容性、安定性および遷移の観察

Autor: Kosorygin, Vladimir S.
Jazyk: angličtina
Rok vydání: 2000
Předmět:
Zdroj: 航空宇宙技術研究所特別資料 = Special Publication of National Aerospace Laboratory. 47:57-60
ISSN: 0289-260X
Popis: 27-28 Sept. 1999 (25th). 27-28 Mar. 2000 (26th)
境界層遷移に影響を与える擾乱の実際の物理的機構を理解するために、境界層内の層流-乱流遷移の位置に影響する音波、乱流、および表面欠陥や表面振動に起因する擾乱などの主流撹乱を研究した。実験は、アルミ合金板から作製した2枚の平板モデルを用いて低乱流閉回路風洞中で実施した。遷移の初生は表面摩擦の上昇を計測して決定した。主流乱れはモデルの上流に設置したスクリーンを使って発生させ、主流音響擾乱は平板から下流に設置したスピーカを用いて導入した。主流および境界層における計測は自然バックグラウンド擾乱および音響励起下で行った。人工音場の影響下における不安定なTS(Tollmien-Schlichting)波発生源と遷移の課題を研究するため、平板境界層を用いた実験では音波受容性の計測に新規方法を適用した。平滑平板境界層の前縁受容性を定性的に研究するための実験を行った。スクリーンにより増強された主流乱れは境界層の内側で典型的な振動分布の変形を起こすことが分かった。遷移の筋書きは低撹乱主流で観察した遷移と類似している。主流乱れは音響受容性を変化させず、また局所受容性の全係数は上昇乱流下では主流撹乱の音波成分の転換により主として決まることが明らかになった。
The free stream disturbances, such as sound, turbulence and the disturbances due to the defects of surface and the surface vibrations, which are to influence on the location of laminar-turbulent transition in the boundary layers, have been studied in order to understand real physical mechanism of disturbances to affect boundary layer transition. The experiments were conducted in a low turbulence close-circuit wind tunnel using two flat plates model made of aluminum alloy sheet. The onset of transition was determined by measuring the rise in skin friction. The free stream turbulence was generated by means of the screen placed upstream from the model and the free stream acoustic disturbances were introduced using a loudspeaker placed downstream from the flat plates. Measurements in the free steam and boundary layer were carried out with natural background disturbance as well as under acoustic excitation. A new method to measure the sound receptivity was applied in experiments with flat plate boundary layer in order to study a problem of unstable TS (Tollmien-Schlichting) waves origin and transition under the influence of an artificial sound field. The experiments on the qualitative study of leading edge receptivity of the smooth flat plate boundary layer were carried out. It was found that the free stream turbulence enhanced by means of a screen had led to typical distortion of oscillation profiles inside the boundary layer. The scenario of transition was similar to that was observed in low-disturbed free steam. It is revealed that the free stream turbulence does not change the acoustical receptivity, and that the total coefficient of the localized receptivity is mainly determined by conversion of sound component of free stream disturbances under the elevated turbulence.
資料番号: AA0028636018
レポート番号: NAL SP-47
Databáze: OpenAIRE
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