Effects of helicity and system rotation on decaying homogeneous turbulence

To consider the nonreflection property of the turbulence statistics in a rotating system, a new method has been proposed to introduce turbulence helicity into an isotropic turbulent field for direct numerical simulation (DNS). Effects of the helicity and the rotation on turbulence statistics and vortex structure are investigated by theoretical analysis and DNS of the homogeneous decaying turbulence. Although DNS results show that both the rotation and the helicity inhibit energy decay, theoretical analysis reveals the occurrence of very different mechanisms for the rotation and the helicity for producing the inhibition effect. The helicity directly decreases the energy transfer while the rotation suppresses the energy transfer due to the so-called scrambling effect. The other effect of system rotation is that rotation elongates the vortex structure along the rotation axis, however, the presence of the helicity appears to weaken this tendency.