This volume brings together lecture notes from the two most recent editions of the EMS Summer School Mathematical Aspects of Fluid Flows, held in Ka?ov, Czech Republic, in May 2019 and 2024. The lectures were taught by leading experts in various fields of mathematical fluid mechanics and offer the current state of the art and emerging trends in the field.

The book is organized into two parts:

Part I features lecture notes from the 2024 edition, covering quantum fluids, mathematical models of tumor growth, and fluid mixtures?each explored from a mathematical perspective.

Part II includes two contributions from the 2019 edition, whose publication was delayed due to the Covid-19 pandemic. These chapters focus on the regularity theory of compressible and incompressible fluid flows, giving an interesting overview of the developments in the field.

This volume is an ideal resource for graduate students, early-career researchers, and specialists working in partial differential equations, fluid mechanics, and related areas.