NUMERICAL AND EXPERIMENTAL STUDIES OF SELF-SUSTAINED OSCILLATORY FLOWS IN COMMUNICATING CHANNELS

A combined numerical and experimental investigation of flow fields and thermal phenomena in communicating channels is performed to gain insight into the operation of compact heat exchange surfaces with interrupted plates. The geometric parameters are selected to excite and sustain the normally damped Tollmien-Schlichting modes. As a result, traveling waves are observed at relatively low Reynolds numbers, inducing self-sustained oscillatory flows that significantly enhance mixing. The critical Reynolds number at which oscillations are first observed in the periodic, fully developed flow region is determined. The numerical results are obtained by direct numerical simulation of the time-dependent energy and Navier-Stokes equations using a spectral element-Fourier method. The oscillatory heat transfer phenomenon is visualized experimentally using real-time, holographic interferometry. For periodic, fully developed flow conditions, the temperature fields are recorded utilizing high-speed cinematography. The experimental visualizations of the thermal waves verify the numerical predictions of the thermal-fluid structure and evolution of communicating-channels flows.