In this seminar, I will present a study on the small-scale temperature structure measured in two research facilities: the LACIS-T wind tunnel (TROPOS, Germany) and the Π Chamber (Michigan Tech, USA). The presentation will utilize both basic statistical tools and advanced spectral analysis to demonstrate how the scalar field evolves under different thermodynamic conditions.

The LACIS-T facility is one of the newest operational aerosol–cloud research chambers. As a closed-loop wind tunnel, it facilitates turbulent, isobaric mixing of two humidified, aerosol-free air streams under independently controlled and repeatable thermodynamic conditions. I will present results from two dry experiments conducted with temperature differences of 25 K and 16 K between the streams. These experiments reveal intensified scalar field variability across the mixing dimension, identify four distinct spectral regimes, and provide a comparative analysis between scalar and energy spectrum.

In contrast, the Π Chamber is a convection-cloud chamber that operates on the principle of induced Rayleigh-B.nard convection, where air is heated from below and cooled from above. This study examines temperature fluctuations under three different temperature differences between the bottom and the top (10 K, 15 K, and 20 K), corresponding to a Rayleigh number of approximately 109 and a Prandtl number of about 0.7. The analysis reveals significant variability in both standard deviation and skewness of temperature fluctuations near the top and bottom plates as well as in the central region—variations that were linked to local thermal plume dynamics. Additionally, three spectral regimes are identified, and a power-law relationship is established between the periodicity of the large-scale circulation and the temperature difference. Notably, the experimental results align well with Direct Numerical Simulations conducted under similar thermodynamic conditions.

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https://uw-edu-pl.zoom.us/j/91014685771?pwd=SVzn38CAlu4H1HgjTUNSnkVheZKhNj.1

Meeting ID: 910 1468 5771
Passcode: 255807