A STUDY OF THE MECHANISMS OF HEAT TRANSFER IN OSCILLATING FLOW

Abstract
Measurements were made in a turbulent, unsteady environment provided within a duct which was placed in longitudinal mode resonance by a siren arrangement. Importance of the velocity antinode locations and the degree of flow reversal in the enhancement of heat transfer was indicated. Measurement techniques utilized a steam-heated axially-segmented test section which covered more than one wave length of the imposed oscillations; and constant-temperature hot-wire probe surveys of the core and boundary layer in both the steady-state and unsteady duct environments. Measurements were compared with other applicable research. The important parameters were outlined together with a quasi-steady analysis. The mechanism which best correlated the experimental measurements and analyses was the effect of the oscillations on the turbulence exchange properties, while viscous dissipation and acoustic streaming appeared to be unimportant for many cases of interest. Total (eddy plus molecular) viscosity plots indicated regions of generation of 'abnormal' turbulence and subsequent diffusion and decay.

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