Weak solutions for a bioconvection model related to Bacillus subtilis

Abstract

We consider the initial-boundary value problem for the coupled Navier- Stokes-Keller-Segel-Fisher-Kolmogorov-Petrovskii-Piskunov system in two- and three- dimensional domains. The problem describes oxytaxis and growth of Bacillus sub- tilis in moving water. We prove existence of global weak solutions to the problem. We distinguish between two cases determined by the cell diusion term and the space dimension, which are referred to as the supercritical and subcritical ones. At the rst case, the choice of the kinetic function enjoys wide range of possibilities: in particular, it can be zero. Our results are new even at the absence of the kinetic term. At the second case, the restrictions on the kinetic function are less relaxed: for instance, it cannot be zero but can be Fisher-like. In the case of linear cell diusion, the solution is regular and unique provided the domain is the whole plane. In ad- dition, we study the long-time behaviour of the problem, nd dissipative estimates, and construct attractors.