Stability on a 3D incompressible Oldroyd-B model with mixed partial dissipation
摘要
The Oldroyd-B equations model viscoelastic fluids. Attention here is focused on a three-dimensional (3D) Oldroyd-B system with mixed dissipation, horizontal velocity dissipation and vertical diffusion for the non-Newtonian stress tensor τ. The equation of τ has no damping, a setup relevant to high Weissenberg viscoelastic flows. In this paper, we solve the small-data global well-posedness and the stability problem in the Sobolev space H2(ℝ3). The lack of the horizontal dissipation or damping in the equation of τ makes the problem almost impossible. This paper discovers that the coupling and interaction of the fluid velocity u and τ generates extra smoothing and stabilization. Mathematically, u and ℙ∇· τ satisfy a system of wave equations, which provides the desired enhanced dissipation. Here, ℙ = I − ∇∆−1∇· denotes the projection onto divergence-free vector fields. In addition, time-weighted energy functionals are introduced to control low-regularity terms. The second major result of this paper establishes optimal decay rates by making use of the aforementioned enhanced dissipation and the integral representation.