The experimental investigation on dynamic response of free surface for non-isothermal liquid bridge with the varying shear airflow

Abstract

Through high-speed camera and the self-developed software package for interface recognition, the space-time evolution of free surface has been investigated for non-isothermal liquid bridge with shear airflow, and the dynamic response of free surface to the shear airflow has also been analyzed. When the shear airflow is induced from the upper disk (u < 0), the convex part of free surface is oppressed downward to the gas side by the shear airflow, which increases the curvature of concave part on the free surface. Under the condition of u > 0, the convex part of free surface is pulled upward to the gas side by the shear airflow, which also exacerbates the curvature of concave part on the free surface. The experimental results show that the shear airflow is introduced from upper disk increasing the probability of dam break for the liquid bridge. The deformation of free surface is intensified with the accelerated shear airflow. Due to the different initial free surface shapes (different volume ratios), the direction and intensity of shear stress vary at the different positions of free surface, and the dynamic response law of the free surface deformation is also different. For a liquid bridge with the volume ratio less than 1 (V = 0.802, V = 0.899), the deformation of free surface presents a certain sinusoidal rule. When the volume ratio of liquid bridge is larger than 1 (V = 1.071), under shear airflow induced from upper disk, the deformation of free surface is still presents sinusoidal rule. When the velocity of shear airflow is u > 0 (u = 1 m/s, u = 1.5 m/s, u = 2.0 m/s), the convex part of free surface moves up by the lifting action of shear airflow, and the shape of free surface presents multi-peak structure. For the liquid bridge with the large aspect ratio (Γ = 1.4), the convex region occupies most part of the interface, and there is no change for the free surface shape under the effect of shear airflow. The free surface shape still presents upper concave and lower convex. With the decreasing aspect ratio (Γ = 1.2), the deformation of free surface is intensified, and the shear airflow can excite obvious fluctuation on the free surface.