Time Resolved PIV of the Flow Field Underneath an Accelerating Meniscus

Abstract

We present an experimental analysis of the flow field near an accelerating contact line using time-resolved Particle Image Velocimetry (TR-PIV). Both advancing and receding contact lines are investigated. The analyzed configuration consists of a liquid column that moves along a vertical 2D channel, open to the atmosphere and driven by a controlled pressure head. Large counter-rotating vortices were observed and analyzed in terms of the maximum intensity of the Q-field. To compute smooth spatial derivatives and improve the measurement resolution in the post-processing stage, we propose a combination of Proper Orthogonal Decomposition (POD) and Radial Basis Functions (RBF). The RBFs are used to regress the spatial and temporal structures of the leading POD modes, so that “high-resolution” modes are obtained. These can then be combined to reconstruct high-resolution fields that are smooth and robust against measurement noise and amenable to analytic differentiation. The results show significant differences in the flow topology between the advancing and the receding cases despite velocity and acceleration of contact lines are comparable in absolute values. This suggests that the flow dynamics are tightly linked to the shape of the interface, which significantly differs in the two cases.

SPICY: a Python toolbox for meshless assimilation from image velocimetry using radial basis functions

“…The solver currently implemented is a minor variant of the direct approach proposed in the original publication. Ongoing works are the extension to Reynolds average formulation to treat turbulent flows, as presented by Sperotto et al (2022a) and the implementation of a Partition of Unity (PUM) approach to limit the memory usage, as by Ratz et al (2022).…”