Lagrange Structure and Dynamics for Solutions to the Spherically Symmetric Compressible Navier-Stokes Equations |
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Authors: | Zhenhua?Guo Email author" target="_blank">Hai-Liang?LiEmail author Zhouping?Xin |
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Institution: | 1.Center for Nonlinear Studies and Department of Mathematics,Northwest University,Xi’an,P.R. China;2.Department of Mathematics,Capital Normal University,Beijing,P.R. China;3.Institute of Mathematical Science,The Chinese University of Hong Kong,Shatin,Hong Kong |
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Abstract: | The compressible Navier-Stokes system (CNS) with density-dependent viscosity coefficients is considered in multi-dimension,
the prototype of the system is the viscous Saint-Venat model for the motion of shallow water. A spherically symmetric weak
solution to the free boundary value problem for CNS with stress free boundary condition and arbitrarily large data is shown
to exist globally in time with the free boundary separating fluids and vacuum and propagating at finite speed as particle
path, which is continuous away from the symmetry center. Detailed regularity and Lagrangian structure of this solution have
been obtained. In particular, it is shown that the particle path is uniquely defined starting from any non-vacuum region away
from the symmetry center, along which vacuum states shall not form in any finite time and the initial regularities of the
solution is preserved. Starting from any non-vacuum point at a later-on time, a particle path is also uniquely defined backward
in time, which either reaches at some initial non-vacuum point, or stops at a small middle time and connects continuously
with vacuum. In addition, the free boundary is shown to expand outward at an algebraic rate in time, and the fluid density
decays and tends to zero almost everywhere away from the symmetry center as the time grows up. This finally leads to the formation
of vacuum state almost everywhere as the time goes to infinity. |
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