  There is very limited knowledge of the kinematical relations for the velocity
structure functions higher than three. Instead, the dynamical equations for the
structure functions of the velocity increment are obtained from the Navier
Stokes equation under the assumption of the local homogeneity and isotropy.
These equations contain the correlation between the velocity and pressure
gradient increments, which is very difficult to know theoretically and
experimentally. We have examined these dynamical relations by using direct
numerical simulation data at very high resolution at large Reynolds numbers,
and found that the contribution of the pressure term is important to the
dynamics of the longitudinal velocity with large amplitudes. The pressure term
is examined from the view point of the conditional average and the role of the
pressure term in the turbulence dynamics is discussed.
