In the paper, the mixing power and distributions of velocity and velocity pulsations in a baffled stirred tank with a flat blade turbine impeller placed at different distances from the bottom were determined. It was found that the mixing power reaches minimum values when the relative clearance of the impeller is C/D = 0.6÷0.7. The investigations of velocity distributions using the PIV method showed the axial flow of the liquid through the impeller. This results in deviations from the typical radial-circumferential flow and changes in mixing power vs. impeller clearance versus a Rushton impeller. With a clearance corresponding to the minimum power, the flow is axial-circumferential with one circulation loop. For a flat blade turbine impeller, good mixing conditions are obtained for a clearance of 0.8 < C/D < 0.9.

This paper is a continuation of the previous one (Widera, 2024. Acta Geologica Polonica, 74 (1), e2). A new, alternative interpretation of the tectonic development of two lignite-rich deposits in the Lubstów and Kleszczów grabens in central Poland is presented. The maximum thickness of lignite mined from both deposits is >86 and >250 m, respectively. These grabens were selected for detailed tectonic analysis because syn-depositional or post-depositional tectonic uplift is undeniably evident. The current study focuses on the distinction between tectonic subsidence/uplift and autocompactional subsidence, and on the timing of their occurrence. Such a research approach allows for the presentation of new conceptual models of Cenozoic tectonic evolution during the formation of the third, very thick, Ścinawa lignite seam (ŚLS-3) and the second Lusatian lignite seam (LLS-2). As a result, it is shown here that the magnitude of both the downward and upward tectonic movements are significantly smaller than previously thought. This new interpretation is also confirmed by the low rank of lignite coalification and the net calorific value of the ŚLS-3 and LLS-2.