  In isotropic helical turbulence, a new single helical model is suggested for
large eddy simulation. Based on the Kolmogrov's hypotheses, the helical model
is proposed according to the balance of helicity dissipation and the average of
helicity flux across the inertial range, and the helical model is a kind of
eddy viscosity model. The coefficient of the helical model is constant and can
be also determined dynamically. Numerical simulations of forced and decaying
isotropic helical turbulence demonstrate that the helical model predicts the
energy and helicity evolution well. The statistical character of the helical
model is closer to the DNS results.In a priori test, the energy and helicity
dissipations of the helical model also show a good results. In general, the
helical model has the advantage contrast with the dynamic Smogorinsky and mixed
models.
