Direct numerical simulations were conducted to investigate the behavior of heavy particles in homogeneous isotropic turbulence. The present study focused on the effect of particle inertia on the autocorrelations of the particle velocity and the fluid velocity seen by particles and the dispersion characteristics of particles. The Lagrangian integral time scale of particles monotonically increased as the magnitude of the particle response time increased

while that of the fluid seen by particles remained relatively constant.It reached maximum when the particle response time was close to the Kolmogorov time scale of the flow. Particle dispersion increased as the particle inertia increased for small particles;while for larger particles

it decreased as particle inertia increased.Particle eddy diffusion coefficient was maximal and greater than that of the fluid by about 30% when the preferential concentration was most obvious. The concentration field of the particles with τp/τk≈1.0 showed that particles tended to be collected in regions of low vorticity (high strain) due to preferential concentration.