Creation of streaks using heating patterns

Abstract

Streaks and rolls are of interest in mixing intensification. It is shown that they can be created in a controlled manner in fully developed shear layers using spatially distributed heating with their spatial distribution dictated by the heating pattern. The method works for any Reynolds number and any heating intensity. The energy costs of streak formation were determined for laminar flows both in terms of additional pressure losses required to drive the same flow rate in the heated and isothermal channels and in terms of the reduction of the flow rate if the pressure gradient remained unaltered. Streak-increased heat transfer across the shear layer has been determined. The creation of streaks using the Rayleigh–Bénard instability was studied for completeness—a heating intensity exceeding the critical Rayleigh number was required, with the spatial structure of the streaks dictated by the critical wavenumber.