  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 approximately 670 to 6200. The exponent is a measure of
sign-singularity and 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 do not depend on the
global helicity of the flow.
