Analysis of three-dimensional thermocapillary flows during PCM melting in large aspect ratio containers in microgravity using POD

Identifier:  imarina:9462597

Handle: https://hdl.handle.net/20.500.11797/imarina9462597

Authors:  Sanchez, P Salgado; Ruiz, X; Massons, J; Porter, J; Ezquerro, J M; Gavalda, Jna

Abstract:
The three-dimensional thermocapillary-driven melting of a phase change material (PCM) in a large-aspect-ratio cuboidal domain in microgravity is investigated numerically. The dynamics within the liquid phase is characterized by various mode transitions that can affect the heat transfer rate. Here we describe the types of melting dynamics that can occur with a selection of three different applied temperature differences Delta T and four different choices of container width W. A proper orthogonal decomposition (POD) method using Singular Value Decomposition (SVD) is applied to determine the dominant modes that describe the melting process, with particular attention to the transition to oscillatory flow. It is found that the oscillatory dynamics are typically associated with an interaction between oblique and longitudinal hydrothermal traveling waves, and that the latter have a slightly lower frequency. The leading-order oscillatory modes may be symmetric with respect to the lateral midplane or not, depending on the applied temperature and the spanwise aspect ratio. Mode (frequency) splitting is sometimes observed, as well as secondary harmonic modes satisfying a 1:2 spatiotemporal resonance condition. These results show that PCM melting is a complex dynamical process involving competition among various hydrothermal traveling waves with distinct orientation and that symmetry-breaking and spatiotemporal resonance play prominent roles in the mode selection problem.