  In recent years, there has been a spike in the interest in multi-phase tissue
growth models. Depending on the type of tissue, the velocity is linked to the
pressure through Stoke's law, Brinkman's law or Darcy's law. While each of
these velocity-pressure relations has been studied in the literature, little
emphasis has been placed on the fine relationship between them. In this paper,
we want to address this dearth in the literature, providing a rigorous argument
that bridges the gap between a viscoelastic tumour model (of Brinkman type) and
an inviscid tumour model (of Darcy type).
