BLOWUP OF SMOOTH SOLUTIONS TO THE COMPRESSIBLE NAVIER-STOKES EQUATIONWITH COMPACT DENSITY

We present a sufficient condition on the blowup of smooth solutions to the compressible Navier-Stokes equations in arbitrary space dimension s with initial density of compact support. As an immediate application , it is shown that any smooth solutions to the compressible Navier-Sto kes equations for polytropic fluids in the absence of heat conduction will blow up in finite time as long as the initial densities have comp act support, and an upper bound, which depends only on the initial dat a, on the blowup time follows from our elementary analysis immediately . Another implication is that there is no global small (decay in time) or even bounded (in the case that all the viscosity coefficients are positive) smooth solutions to the compressible Navier-Stokes equations for polytropic fluids, no matter how small the initial data are, as l ong as the initial density is of compact support. This is in contrast to the classical theory of global existence of small solutions to the same system with initial data being a small perturbation of a constant state that is not a vacuum. The blowup of smooth solutions to the com pressible Euler system with initial density and velocity of compact su pport is a simple consequence of our argument. (C) 1998 John Wiley & S ons, Inc.