Long-time Existence and Incompressible Limit of Weak and Classical Solutions to the Cauchy Problem for Compressible Navier-Stokes Equations with Large Bulk Viscosity Coefficient and Large Initial Data (2507.02497v1)

Abstract: This paper investigates the Cauchy problem for the barotropic compressible Navier-Stokes equations in $\mathbb{R}^2$ with the constant state as far field, which could be vacuum or nonvacuum. Under the assumption of a sufficiently large bulk viscosity coefficient, we establish the long-time existence of weak, strong, and classical solutions, without imposing any extra restrictions on the initial velocity divergence. Moreover, we demonstrate that the solutions of the compressible Navier-Stokes equations converge to solutions of the inhomogeneous incompressible Navier-Stokes equations, as the bulk viscosity coefficient tends to infinity. The incompressible limit of the weak solutions holds even without requiring the initial velocity to be divergence-free. The key obstacle in the Cauchy problem is the failure of the Poincar\'e's inequality. This could be resolved by introducing a time-dependent Poincar\'e's type inequality, but it needs imposing weighted-integrability conditions on the initial density.