Comparison of Two Unstable Flow States in Turbulent Mixed Convection

We present an experimental study focusing on the large- and small-scale structures in turbulent mixed convection. Measurements are conducted at stable conditions and during a reconfiguration event using temperature probes and triggered stereoscopic particle image velocimetry. It is found that the amplitude of the temperature distribution is higher for a state with three Large-Scale Circulations (LSC) than for a state with four LSCs. Furthermore, a correlation analysis of velocity fields measured during a reconfiguration process reveals the change of the dominant LSC mode. However, the mean spatial power distribution computed via a fast Fourier transformation reflects no changes in small-scale flow structures.