Measurements and characterization of wall-pressure fluctuations on cylinders in a bundle in turbulent axial flow; Part 1: Spectral characteristics

Abstract

This paper (Part 1) presents measurements, in the frequency domain, of turbulent wall-pressure fluctuations in a square array of cylinders in axial flow. The motivation for making these measurements was to provide input information for an analytical model of the dynamics of clusters of cylinders in axial flow. Accordingly, a great deal of effort has been devoted to the characterization of the power-spectral densities (PSD's) and cross-spectral densities (CSD's) of the measured pressure fluctuations into a suitable form for utilization in the theory; ultimately, the experimental data is transformed into force-per-unit-length CSD's derived from the wall-pressure CSD's. These latter, although intricate by nature because of the complexity of the cross-sectional geometry of the bundle, may nevertheless be described approximately by simple analytical functions. Longitudinal and lateral (i.e., azimuthal) characteristics of the turbulent wall-pressure field are obtained, and their dependence on Reynolds and Strouhal numbers and azimuthal orientation on the cylinders is discussed. Furthermore, the turbulent flow characteristics determined here are compared to those available for pipe and annular flows. Part 2 of this paper presents the complementary, temporal characteristics of the wall-pressure field.