DYNAMICS AND KINEMATICS OF MOVEMENT OF THE MENISCUS OF LIQUID IN THE CAPILLARY

The role of capillary pressure as a factor determining the dynamics and kinematics of the capillary flow is considered. The observed axial flow is considered as a consequence of the radial flow of the fluid bordering the surface of the meniscus. It is shown that the radial flow is due to the gradient of the superficial tension of the meniscus caused by the deformation of the meniscus surface by the forces of fluid adhesion to the capillary wall. An estimate of current velocities is given. Under typical conditions, the velocity of the radial flow is by a factor of ten greater than the flow velocity along the capillary axis when the volume velocities calculated from the values of the tension gradient and the capillary pressure, respectively, are equal. It is concluded that the observed movement of the meniscus is caused by the flow of fluid on the surface of the capillary, in which the axial component of the flow rate on the capillary wall is zero. This eliminates the contradiction between the apparent movement of the meniscus and the equation of the axial flow of fluid in the capillary, according to which the speed on the wall should be zero