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Turbulence and Shear Flow Phenomena -1 First International Symposium

ISBN:
1-56700-135-1 (Print)

WALL PRESSURE FLUCTUATIONS IN SEPARATED AND REATTACHING FLOWS OVER A BACKWARD-FACING STEP

Inwon Lee
Department of Mechanical Engineering Korea Advanced Institute of Science and Technology; Advanced Ship Engineering Research Center (ASERC), Pusan National University San 30, Jangjeon-dong, Gumjeong-gu, Busan 609-735, South Korea

Hyung Jin Sung
Department of Mechanical Engineering, KAIST 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Korea

Abstract

Measurements were made of the wall pressure fluctuations in separated and reattaching flows over a backward-facing step. A new type of an array of pressure sensors, composed of PVDF (polyvinylidenefluoride), was employed to measure the spatio-temporal features of wall pressure field. Distributions of the root-mean-square (rms) pressure fluctuations as well as the pressure spectra and coherence of the surface pressure field were measured at various locations near the reattachment region. The experimental results showed that the level of fluctuating pressure rises rapidly in the downstream direction, reaching a maximum value near reattachment. As the reattached flow convects downstream, the low frequency content of the pressure spectrum decreases and the high frequency increases. A large-scale, convective spatial structure undergoes a relaxation process, evolving from its highly energized state at reattachment back toward an equilibrium.