Flow rate limitation in curved open capillary groove channels

Abstract

This paper is concerned with the forced flow through curved open capillary channels under microgravity conditions. A maximum flow rate in the open capillary channel achieves when the flow rate exceeds a certain value and the free surface collapses leading to the gas ingestion. The gas ingestion is not desired for most of the applications. In order to prevent it and enable an optimal performance, it is vital to understand the influences of the channel geometry parameters and liquid properties on the maximum flow rate. In this paper, the one-dimensional theoretical model successfully applied to the straight open capillary channel is extended to the curved open capillary channel. The result shows that under the same boundary conditions, the maximum flow rate in the curved open channel is smaller than that in the straight open channel. The maximum flow rate decreases with the curvature of open channel increasing. By analysis, the pressure loss and the centrifugal force effect due to the curve motion in a curved path are considered to be the cause of the maximum flow rate difference between the curved channel and the straight channel. It is found that the centrifugal force effects weaken the pressure difference balance ability of the free surface and the pressure loss in the curved open channel is greater than that in the straight open channel. By comparison, the one-dimensional theoretical results agree well with CFD simulations and the average relative error is only 1.51%. Furthermore, the parametric study of flow in the curved open capillary channel depicts that the maximum flow rate increases with the channel curvature or aspect ratio increasing, and decreases with the open channel length, contact angle or Ohnesorge number increasing. This conclusion can be utilized to design the open channel in space liquid management system.