JAMSTEC > 地球情報基盤センター > 研究者のページ > セミナー情報



  第14回 CEISTセミナー

場所:横浜研究所 シミュレータ研究棟1階 会議室
講師:Dr. Pedro Valente (リスボン大学高等技術研究院・講師)


New perspectives on equilibrium and non-equilibrium turbulence theory and modelling.
Turbulence is nature's way of speeding up molecular transport in fluids and plasmas by generating multiscale random motions, and is crucial for a diverse range of phenomena, including rain initiation, the formation of planets, and predator-prey or mating interactions. It is widely accepted that the induced motions are fed by a continuous range of larger-scale motions (the energy cascade cite{Frisch:book,MY2010}), and are always sufficiently fine-scale to make molecular transport efficient (the dissipation anomaly).
An essential ingredient underlying turbulence models and theories is that these fine-scale turbulent motions are very fast-paced and thus instantaneously adjust to dissipate whatever energy they are fed. This near-instantaneous adjustment, however, is yet to be observed - a fact that is usually attributed to insufficiently high Reynolds number data or the indirect consequence of energy transfer delays.
In this talk, the basic underlying mechanism preventing the near-instantaneous adjustment is argued to stem from the power required to induce or annihilate fine scale motions. This mechanism is present regardless of transfer delays and is applicable to a wide range of Reynolds numbers. This simple missing piece explains the discrepancies in normalized energy dissipation rates in stationary and non-stationary turbulent flows as well as examples of non-equilibrium dissipative behaviour observed in recent experiments.
This new physical mechanism motivates a new paradigm of urbulence modelling with applications in engineering, geophysics and astrophysics.

大西 領