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Inclined turbulent thermal convection in liquid sodium is studied at large Rayleigh numbers$Ra\\gtrsim 10^{7}$based on the results of both experimental measurements and high-resolution numerical simulations. For a direct comparison, the considered system parameters are set to be similar:$Ra=1.67\\times 10^{7}$in the direct numerical simulations (DNS),$Ra=1.5\\times 10^{7}$in the large-eddy simulations and$Ra=1.42\\times 10^{7}$in the experiments, while the Prandtl number of liquid sodium is very small ($Pr\\approx 0.009$). The cylindrical convection cell has an aspect ratio of one; one circular surface is heated, while the other one is cooled. Additionally, the cylinder is inclined with respect to gravity and the inclination angle varies from$\\unicode[STIX]{x1D6FD}=0^{\\circ }$, which corresponds to Rayleigh–Bénard convection (RBC), to$\\unicode[STIX]{x1D6FD}=90^{\\circ }$, as in a vertical convection (VC) set-up. Our study demonstrates quantitative agreement of the experimental and numerical results, in particular with respect to the global heat and momentum transport, temperature and velocity profiles, as well as the dynamics of the large-scale circulation (LSC). The DNS reveal that the twisting and sloshing of the LSC at small inclination angles periodically affects the instantaneous heat transport (up to$\\pm 44\\,\\%$of the mean heat transport). The twisted LSC is associated with a weak heat transport, while the sloshing mode that brings together the hot and cold streams of the LSC is associated with a strong heat transport. The experiments show that the heat transport scales as$Nu\\sim Ra^{0.22}$in both limiting cases (RBC and VC) for Rayleigh numbers around$Ra\\approx 10^{7}$, while any inclination of the cell,$0<\\unicode[STIX]{x1D6FD}\\leqslant 90^{\\circ }$, leads to an increase of $Nu$.

Inclined turbulent thermal convection by large Rayleigh numbers in extremely small-Prandtl-number fluids is studied based on results of both, measurements and high-resolution numerical simulations. The Prandtl number \\(Pr0.0093\\) considered in the experiments and the Large-Eddy Simulations (LES) and \\(Pr=0.0094\\) considered in the Direct Numerical Simulations (DNS) correspond to liquid sodium, which is used in the experiments. Also similar are the studied Rayleigh numbers, which are, respectively, \\(Ra=1.6710^7\\) in the DNS, \\(Ra=1.510^7\\) in the LES and \\(Ra=1.4210^7\\) in the measurements. The working convection cell is a cylinder with equal height and diameter, where one circular surface is heated and another one is cooled. The cylinder axis is inclined with respect to the vertical and the inclination angle varies from \\(=0^\\), which corresponds to a Rayleigh-Bénard configuration (RBC), to \\(=90^\\), as in a vertical convection (VC) setup. The turbulent heat and momentum transport as well as time-averaged and instantaneous flow structures and their evolution in time are studied in detail, for different inclination angles, and are illustrated also by supplementary videos, obtained from the DNS and experimental data. To investigate the scaling relations of the mean heat and momentum transport in the limiting cases of RBC and VC configurations, additional measurements are conducted for about one decade of the Rayleigh numbers around \\(Ra=10^7\\) and \\(Pr0.009\\). With respect to the turbulent heat transport in inclined thermal convection by low \\(Pr\\), a similarity of the global flow characteristics for the same value of \\(RaPr\\) is proposed and analysed, based on the above simulations and measurements and on complementary DNS for \\(Ra=1.6710^6\\), \\(Pr=0.094\\) and \\(Ra=10^9\\), \\(Pr=1\\).

Silicon carbide films on porous-Si/Si substrates have attracted considerable attention due to their potential use in modern high-power electronic devices. Here, SiC/porous-Si/Si heterostructures fabricated by an atomic substitution method are investigated. Scanning electron microscopy shows the formation of a continuous about 40 nm thick film of SiC, with a sharp interface to the porous Si sublayer. Energy-dispersive x-ray spectroscopy confirmed that Si, C, and O are the only constituents of the SiC film and the porous-Si underlayer. Raman spectroscopy indicated 3C and 6H polytypes in the SiC film. Spectroscopic ellipsometry in the range of 0.6–5.1 eV was performed in order to determine the refractive index (n), extinction coefficient (k), and bandgap (Eg) of the SiC layer. Macro-FTIR transmission spectra showed the expected absorption features of SiC. IR reflectance maps measured with nano-resolution reveal lateral inhomogeneities of the intensity, which we attribute to the morphology of the porous silicon sublayer. Numerical simulations of the local near-field response were performed for regions, where the SiC layer lay directly on silicon and for regions where it is free-standing over pores. The simulation results are in close agreement with the experimental observations obtained by nanoFTIR and confirm that the porous substrate plays a decisive role in determining the local optical and structural properties of the SiC/porous-Si/Si heterostructures.