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 inve stigated 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 lo ngitudinal pitch ratios of 2.1, 1.6 and 2.1 respectively. The mean vel ocities, turbulence levels, spectra, time and length scales and dissip ation rates were determined from ensemble-averaged and time-resolved l aser Doppler anemometry (LDA) measurements. The pressure drop across t he bundles was also measured. The staggered arrays were found to gener ate higher levels of turbulence and a higher pressure drop. Turbulence kinetic energy reaches a maximum downstream of the second row in stag gered 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 lo wer r.m.s. levels in the wakes and alteration of the recirculation cha racteristics. A discrete periodicity with a Strouhal number of 0.26 wa s identified in the 3.6 x 1.6 staggered array which is associated with vortex shedding. Turbulence scales and dissipation rates were estimat ed and compared with numerical predictions.