Abstract
This research deals with the fluid force acting on a sphere in a small-diameter tube. It is supposed that such a problem becomes very important when the small-diameter and complex fluid pipelines are designed in many systems of micro machines. The analytical model consists of incompressible viscous flow in a small-diameter tube at low Reynolds number, and spherical pendulum that can move almost perpendicular to the wall of the tube. After constracting the experimental setup in consideration of dynamical similarity, the fluid force acting on a sphere ,the displacement of a sphere, and the fluid velocity were measured by a loadcell, two optical displacement meters and the laser doppler velocimeter, respectively.
