Hypergravity Effect on Dynamic Capillary Flow in Inclined Conical Tubes with Undulated Inner Walls

Capillaries in human brain and plants are often neither straight nor smooth, but exhibit conical tubes with numerous wall undulations. Under hypergravity, the dynamics of blood/water flow in such roughened conical capillaries remains elusive, which may affect the performance and health of pilots/astronauts and the growth of plants. This study aims to establish a theoretical model to characterize dynamic capillary rise in inclined conical tubes having idealized cosine-type undulated inner walls, with hypergravity effect duly accounted for. For validation, full numerical simulations are performed, and good agreement is achieved between theoretical and numerical results. Dynamic capillary rise in undulated conical tubes is shown to be strongly dependent upon three key morphology parameters: undulation amplitude and axial wave number of cosine-type wall, and opening angle (either positive or negative) of conical tube. The steady height of capillary rise decreases with increasing opening angle (positive) and/or increasing undulation amplitude for moderate wave numbers, but increases when the opening angle is negative or the wave number is small. When the wave number becomes sufficiently large, the steady height increases with increasing amplitude and decreases with increasing wave number. In the presence of hypergravity effect, the dynamics of capillary rise in undulated conical tubes for several commonly used liquid types is explored to provide theoretical guidance for practical applications in the fields of aeronautical engineering, space exploitation, and the like.