Validity and applicability of continuum biofilm closure relations

Establish the validity of closure relations for effective biofilm velocity and diffusivity, determine how these relations extend to systems with multiple interacting microbial species, and ascertain their applicability to moderate-Reynolds-number flows.

Background

Continuum biofilm models commonly represent biofilm dynamics using modified diffusion or advection equations. These formulations require closure relations for the effective biofilm velocity and/or diffusivity, often relating them to a biofilm pressure field or assuming potential flow. The paper identifies uncertainty regarding whether such closures are valid beyond the settings in which they were developed.

The unresolved issue has three connected components: validating the closure relations themselves, extending them to multispecies biofilms with interacting microbial populations, and determining whether they remain appropriate for flows with moderate Reynolds numbers. Resolving these questions would clarify the range of physical systems for which continuum biofilm descriptions can be reliably used.