Global existence to a $3D$ chemotaxis-Navier-stokes system with nonlinear diffusion and rotation (1706.02022v1)

Abstract: This paper is concerned with the following quasilinear chemotaxis--Navier--Stokes system with nonlinear diffusion and rotation $$ \left{ \begin{array}{l} n_t+u\cdot\nabla n=\Delta n^m-\nabla\cdot(nS(x,n,c)\cdot\nabla c),\quad x\in \Omega, t>0, c_t+u\cdot\nabla c=\Delta c-nc,\quad x\in \Omega, t>0,\ u_t+\kappa(u \cdot \nabla)u+\nabla P=\Delta u+n\nabla \phi ,\quad x\in \Omega, t>0,\ \nabla\cdot u=0,\quad x\in \Omega, t>0 \end{array}\right.\eqno(CNF) $$ is considered under the no-flux boundary conditions for $n, c$ and the Dirichlet boundary condition for $u$ in a three-dimensional convex domain $\Omega\subseteq \mathbb{R}^3$ with smooth boundary, which describes the motion of oxygen-driven bacteria in a fluid. Here % $\Omega\subseteq \mathbb{R}^3$ is a , $\kappa\in \mathbb{R}$ and $S$ denotes the strength of nonlinear fluid convection and a given tensor-valued function, respectively. Assume $m>\frac{10}{9}$ and $S$ fulfills $|S(x,n,c)| \leq S_0(c)$ for all $(x,n,c)\in \bar{\Omega} \times [0, \infty)\times[0, \infty)$ with $S_0(c)$ nondecreasing on $[0,\infty)$, then for any reasonably regular initial data, the corresponding initial-boundary problem $(CNF)$ admits at least one global weak solution.