INVESTIGATION ON FLUID DYNAMICS IN A CAPILLARY TUBE UNDER MICROGRAVITY BASED ON THE MAGNETIC COMPENSATION EXPERIMENT

Due to the dominance of capillary force, the flow characteristics of fluid in microgravity environment are essentially different from those in normal gravity environment. Based on the principle of magnetic compensation, an experiment platform simulating the flow under microgravity with high tunability is established on the ground. The accuracy of the experimental system is verified by comparing the experimental data with the theoretical models, and the dynamic flow behavior of water-based magnetic fluid in vertical capillary tube under different equivalent gravity levels is studied. By comparing the experimental data with the different theoretical model solutions, the feasibility of using the magnetic compensation method to carry out the investigation on microgravity flow is verified. The average deviation between the experimental results obtained by the magnetic compensation method and the two theoretical model solutions using different dynamic contact angle models is 7.1% and 13.7% respectively. Furthermore, the influence of factors such as pipe diameter, equivalent gravity level and dynamic advancing contact angle on the dynamic flow characteristics in the capillary tube has been quantitatively studied. In a near zero-gravity environment, the flow development process can be divided into three stages where the liquid level hhas a linear relationship with t^2 , t, \sqrt t successively. The pipe diameter has a complicated affect on the capillary climbing process. The influence of pipe diameter on flow does not change linearly with pipe diameter and its influence on the flow velocity is different among flow stages. For the capillary flow in the vertical direction, the greater the equivalent gravitational acceleration, the worse the capillary climbing ability of the magnetic fluid in the tube, and the more difficult it is to observe the existence of the first capillary climbing stage. Under the same conditions, the larger the dynamic advancing contact angle of the fluid, the smaller the capillary climbing velocity.