Two-phase flow dynamics of residual water transport in a front-load washing machine during spin cycle

Abstract Efficient dehydration in washing machines is critical for reducing energy consumption during drying and for preventing hygiene issues from residual moisture. This study investigated the internal flow behavior of residual water in a front-load washing machine, focusing on the mechanisms of upward transport during the spin cycle. A combined experimental and numerical approach was employed. High-speed imaging enabled in-situ observation of droplet motion and pooling, while transient volume of fluid simulations captured the two-phase flow dynamics between the inner and outer tubs. Results identified two distinct mechanisms governing water migration: shear-driven flow, induced by airflow from drum rotation, and adhesive flow, caused by viscous adhesion of water to the inner tub wall. Adhesive flow dominated at higher residual volumes, producing substantial upward transport even at relatively low rotational speeds. Quantitative analysis indicated that residual water volume had a stronger influence on water distribution than drum speed, with larger volumes amplifying upward migration and increasing the risk of re-entrainment. The results were interpreted using a Taylornumber( Ta )-based scaling perspective to quantify the efficiency of shear transmission and the onset of upward water migration during drum rotation.