Effects of Spanwise Wall Oscillations on Heat Transfer and Drag in an Asymmetrically Heated Channel

Flows in next-generation solar receivers are turbulent and strongly anisothermal, with temperature-dependent fluid properties. The aim of this study is to explore and show results of Direct Numerical Simulations (DNS) with a spanwise wall oscillation boundary condition in the context of next generation solar receiver operating conditions. We investigate the dissimilarity between heat transfer and skin friction in a quasi-compressible fluid with asymmetrical heating, constant Prandtl numbers ($Pr=0.76$ and $0.86$) and varying source term that affects the fluid's heating conditions. Using 24 Direct Numerical Simulations (DNS), we assess the influence of six oscillation periods of Spanwise Wall Oscillation (SWO) on flows at different friction Reynolds numbers ($Re_\tau=180,395,800$) and under an imposed temperature source term. Results show how oscillation period, Reynolds number, and thermal conditions impact flow behavior. Notably, a dissimilarity in turbulent heat transfer and skin friction amplitudes emerges for long oscillation periods ($T^+=350,500,650$). Velocity-velocity and velocity-temperature correlations are studied permitting to optimize the heat transfer and drag characteristics in highly anisothermal turbulent flows.