Transitional cylindrical swirling flow in presence of a flat free surface

TL;DR

This paper investigates transitional cylindrical swirling flows with a free surface driven by bottom rotation, revealing new flow states through 3D Navier-Stokes simulations without symmetry assumptions.

Contribution

It provides the first fully 3D numerical solutions of free-surface cylindrical swirling flows without symmetry constraints, uncovering novel flow states.

Findings

Discovered new flow states in transitional regimes.

Used Legendre spectral element method for high-fidelity simulations.

Analyzed flow behavior with open free surface boundary conditions.

Abstract

This article is devoted to the study of an incompressible viscous flow of a fluid partly enclosed in a cylindrical container with an open top surface and driven by the constant rotation of the bottom wall. Such type of flows belongs to a group of recirculating lid-driven cavity flows with geometrical axisymmetry and of the prescribed boundary conditions of Dirichlet type -- no-slip on the cavity walls. The top surface of the cylindrical cavity is left open with an imposed stress-free boundary condition, while a no-slip condition with a prescribed rotational velocity is imposed on the bottom wall. The Reynolds regime corresponds to transitional flows with some incursions in the fully laminar regime. The approach taken here revealed new flow states that were investigated based on a fully three-dimensional solution of the Navier--Stokes equations for the free-surface cylindrical swirling flow, without resorting to any symmetry property unlike all other results available in the literature. Theses solutions are obtained through direct numerical simulations based on a Legendre spectral element method.