Artículos de revistas
Cancellation exponents in helical and non-helical flows
Fecha
2010-04Registro en:
Rodriguez Imazio, Paola Carolina; Mininni, Pablo Daniel; Cancellation exponents in helical and non-helical flows; Cambridge University Press; Journal of Fluid Mechanics; 651; 4-2010; 241-250
0022-1120
CONICET Digital
CONICET
Autor
Rodriguez Imazio, Paola Carolina
Mininni, Pablo Daniel
Resumen
Helicity is a quadratic invariant of the Euler equation in three dimensions. As the energy, when present helicity cascades to smaller scales where it dissipates. However, the role played by helicity in the energy cascade is still unclear. In non-helical flows, the velocity and the vorticity tend to align locally creating patches with opposite signs of helicity. Also in helical flows helicity changes sign rapidly in space. Not being a positive definite quantity, global studies considering its spectral scaling in the inertial range are inconclusive, except for cases where one sign of helicity is dominant. We use the cancellation exponent to characterize the scaling laws followed by helicity fluctuations in numerical simulations of helical and non-helical turbulent flows, with different forcing functions and spanning a range of Reynolds numbers from ≈ 670 to ≈ 6200. The exponent can be related to the fractal dimension as well as to the first-order helicity scaling exponent. The results are consistent with the geometry of helical structures being filamentary. Further analysis indicates that statistical properties of helicity fluctuations in the simulations do not depend on the global helicity of the flow. © 2010 Cambridge University Press.