HELICITY PRODUCTION IN THE TRANSITION TO CHAOTIC FLOW SIMULATED BY NAVIER-STOKES EQUATION

Helicity production in a homogeneous fluid is numerically demonstrated by using steady and unsteady forced Navier-Stokes equations: Even if all Fourier components of the force do not have helicity, nonlinear in teractions of the zero-helicity components can generate helicity in th e flow. When the Reynolds number increases, the flow nature changes fr om steady to temporally periodic to chaotic. The produced helicity has the largest time-averaged value in the periodic motion.