Science Daily July 11, 2023
The effect of turbulence is one of the largest uncertainty factors in modern climate models and weather forecasting. In turbulent flows, kinetic energy is transferred from large spatial scales to small ones, where it is converted to heat by viscosity. For strong turbulence Kolmogorov conjectured in 1941 that this energy transfer is dominated by inertial forces at intermediate spatial scales. Since Kolmogorov’s conjecture, the velocity difference statistics in this so-called inertial range have been expected to follow universal power laws for which theoretical predictions have been refined over the years. An international team of researchers (Germany, USA – Cornell University) has provided experimental results over an unprecedented range of Reynolds numbers in a well-controlled wind tunnel flow produced in the turbulence tunnel. They found that the measured second-order velocity difference statistics became independent of the Reynolds number, suggesting a universal behavior of decaying turbulence. However, they did not observe power laws even at the highest Reynolds number, i.e., at turbulence levels otherwise only attainable in atmospheric flows. According to the researchers these experiments can contribute to a better understanding of turbulence in engineered flows or the atmosphere… read more. TECHNICAL ARTICLE
Difference in the local scaling exponentζ2 at two different values of r within the inertial range…
Credit: Phys. Rev. Lett. 131, 024001, 10 July 2023Â