"Clusterization" and intermittency of temperature fluctuations in turbulent convection.

Temperature time traces are obtained in turbulent thermal convection at high Rayleigh numbers. Measurements are made in the midplane of the apparatus, near the sidewall but outside the boundary layer. A telegraph approximation for temperature traces is generated by setting the fluctuation amplitude to 1 or 0 depending on whether or not it exceeds the mean value.

Local structure of turbulence in flows with large Reynolds numbers.

Results are reported on an experimental investigation of the characteristics of fine-scale pulsations of the velocity in several shear flows (mixing layer, boundary layer, planar, axially symmetric, and spatial wakes, and in the return channel of a large wind tunnel) in an interval of definite Reynolds numbers R(lambda) [approximately-equal-to] 70-3000 with respect to the Taylor microscale lambda. The characteristic scales of most of the studied flows are quite large, and the integral scale of the turbulence reaches 5 m. The apparatus had a high resolving power-the ratio of the hot-wire length to the Kolmogorov scale was varied in the range 0.