# Turbulent Rayleigh-Bénard convection: unrevelead insights into the near-wall transport process

Robert Kaiser

^{1}, Christian Resagk^{1}, Ronald du Puits^{1}^{1}

*Technische Universität Ilmenau, Institut of Thermodynamics and Fluid Mechanics, Germany*

The three dimensional velocity field in the vicinity of the cooling plate inside a Rayleigh-Benard convection cell is experimentally investigated at Rayleigh numbers between \(10^{8}\leq Ra\leq 10^{12}\) using tomographic PIV. This flow region was intensively analysed by direct numerical simulations (Schumacher et al., Shishkina et al., Shi et al.), while experimental data sets of the all velocity components are restricted to a single point (Li et al.). In the past, du Puits et al. have shown that the convective boundary layer is already in a transition to turbulence at \(Ra=10^{10}\), whereas theoretical predictions of the vertical heat flux are assuming either laminar or turbulent boundary approaches. In order to capture the complexity of this strongly three dimensional flow field, we performed tomographic velocity measurements in a volume of \((40x40x20)mm^{2}\) closed to the cooling plate of the Barrel of Ilmenau at different Ra. The results will be presented on the

**Keywords:**Wall-bounded flows, Convection, Turbulence

**Figure 1:**Measurement set-up of the tomographic particle image velocimeter at the cooling plate of the Barrel of Ilmenau: four scientific CMOS cameras \((2560 x 2160)px^{2}\) @ 25Hz in double frame mode, 100mJ double pulse LASER, 5\(\mu m\) aerosol particles of