Simulating research on rod string's gyro effect caused by eccentric rotation in circular tube

Based on the influences of eccentrical rotating inertial centrifugal force and axial force on the rod string's lateral bending deformation, the finite beam element model of rod string's bending deformation is established. The constraint to rod string's bending deflection exerted by inwall of circular tube and the distinction of the constraint to rod string's deflection because of the different gaps between rod string to circular tube and coupling to circular tube are both taken into account. Meanwhile, removable spring elements with two directions are adopted, by which the non-linear contact problem between the rod string and circular tube is well resolved. Combining space beam element and spring elements with two directions, the corresponding finite element simulating program is also developed. Several simulating results can be shown as follows: eccentric rotation of rod string is able to produce gyro effect in vertical circular tube; The shape of the rod string's deformation is a spiral which is thin on the upper-part and dense on the under-part; Gyro wave numbers are affected obviously by rotating speed, eccentricity, axial concentrated force, axial distributed force and length of the rod string.