Head Loss and Flow Characteristics for Turning Flow Driven by Surface Tension Force Inside Open Microchannel

Abstract

Present study demonstrates the head loss and the flow characteristics as the open microchannel makes turns. The microchannels are of various aspect ratios of depth/width ranging from 0.5 to 2, and makes turns with different angles ranging from 60 to 120 degrees. The investigations are performed both by experiments and numerical simulations based on first principle equations. For the open channel system, the flow is mainly driven by surface tension under same pressure atmosphere. For liquid flow in open microchannel without turn, the liquid front velocity decreases but the interface area of liquid-gas increase as flow moves downstream. For turning flows, liquid front velocity is decreased firstly and then increased sharply at the turning point. Furthermore, the liquid front velocity can be increased for higher aspect ratio of channel height and width, and the effect of aspect ratio is significant up to aspect ratio between 1.0–1.5. Detailed flow characteristics as well as the head loss coefficient due to microchannel turning are discussed.