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 […]
Category Archives: Turnulence
Supercomputer used to simulate winds that cause clear air turbulence
Science Daily July 12, 2023 Although clear air turbulence (CAT) generation in the free atmosphere has been studied by high-resolution numerical simulations, few studies simulated aircraft-scale turbulence eddies and validated them with high-frequency airborne observation. Researchers in Japan used a regional numerical weather prediction model to simulate the event with fine resolution. They compared the onboard-recorded data with the virtual flight data, to confirm that turbulent eddies were reasonably reproduced. The CAT was largely generated by breaking Kelvin-Helmholtz (KH) instability waves in the free atmosphere. They resolved the KH waves and their breaking. When the resolution was finer, the turbulent […]
A new approach to controlling the properties of turbulence
Phys.org June 20, 2023 Material boundaries of the experimental apparatus developed to generate turbulence pose a challenge for understanding what the turbulence has been fed and how it would freely evolve. An international team of researchers (USA – University of Chicago, UC Santa Barbara, France) built and controlled a confined state of turbulence using vortex rings. The stationary and isolated blob of turbulence was sustained solely by vortex rings. Thus they assembled a full picture of its three-dimensional structure, onset, energy budget and tunability. The incoming vortex rings could be endowed with conserved quantities, such as helicity, which could be […]
Fiber tracking method delivers important new insights into turbulence
Phys.org September 17, 2021 To measure turbulent flows the movement of tracers that are added to the fluid are tracked. The tracers spread over time, they move far apart, and every particle moves independently. To overcome these issues an international team of researchers (Switzerland, Italy, Sweden) used fibers instead of tracer particles. They created a computer simulation and added rigid fibers of different lengths, which kept the ends of each fiber apart at a fixed distance. By tracking how each fiber moved and rotated within the fluid over time, the researchers were able to build up a picture that encompassed […]