Nobumitsu Yokoi

Abstract In non-mirror-symmetric system, turbulent helicity 〈u′⋅ω′〉 enters the Reynolds-stress expression as the coupling coefficient of the mean absolute vorticity (anti-symmetric part of the mean velocity shear) (u′ : velocity fluctuation, ω′(=∇×u′): vorticity fluctuation, 〈⋯〉 : ensemble average).

Helicities are known to play essential roles in several geophysical, astrophysical, and space plasma phenomena and are thus studied by means of diverse methods from various disciplinary viewpoints. A book recently published in AGU’s Geophysical Monograph Series, Helicities in Geophysics, Astrophysics, and Beyond, discusses the importance of helicities to an array of scientific disciplines and explores how they relate to real world issues.

Abstract : The non-equilibrium property of turbulence modifies the characteristics of turbulent transport. With the aid of response function formalism, such non-equilibrium effects in turbulent transport can be represented by the temporal variation of the turbulent energy (K) and its dissipation rate ( ε ) along the mean stream through the advective derivatives of K and ε . Applications of this effect to the turbulent convection with plumes are considered for the first time in this work.