  Temporal decorrelations in compressible isotropic turbulence are studied
using the space-time correlation theory and direct numerical simulation. A
swept-wave model is developed for dilatational components while the classic
random sweeping model is proposed for solenoidal components. The swept-wave
model shows that the temporal decorrelations in dilatational fluctuations are
dominated by two physical processes: random sweeping and wave propagation.
These models are supported by the direct numerical simulation of compressible
isotropic turbulence, in the sense of that all curves of normalized time
correlations for different wavenumbers collapse into a single one using the
normalized time separations. The swept-wave model is further extended to
account for a constant mean velocity.
