An experimental study of the mean flow and turbulence structure of cross-flow over tube bundles

The velocity characteristics of cross-flow over tube bundles were investigated in a water tunnel. Three tube arrays with a transverse pitch ratio of 3.6 were studied: an in-line and two staggered arrays with longitudinal pitch ratios of 2.1, 1.6 and 2.1 respectively. The mean velocities, turbulence levels, spectra, time and length scales and dissipation rates were determined from ensemble-averaged and time-resolved laser Doppler anemometry (LDA) measurements. The pressure drop across the bundles was also measured. The staggered arrays were found to generate higher levels of turbulence and a higher pressure drop. Turbulence kinetic energy reaches a maximum downstream of the second row in staggered arrays. The wake regions in both geometries are anisotropic with transverse r.m.s. velocities being higher than axial ones. Increasing the longitudinal spacing in the staggered configuration results in lower r.m.s. levels in the wakes and alteration of the recirculation characteristics. A discrete periodicity with a Strouhal number of 0.26 was identified in the 3.6 x 1.6 staggered array which is associated with vortex shedding. Turbulence scales and dissipation rates were estimated and compared with numerical predictions.