Rotation of a slender rod injected into a cylindrical constraint

Abstract

We investigate the buckling of a slender elastic rod injected into a cylindrical constraint while undergoing axial rotation. Particular focus is given to extension of the helical buckling length. This problem is of particular application to coiled tubing operations in the oil and gas industry where helical buckling and eventual lockup occur, thereby preventing complete access to horizontal oil wells. Our approach focuses on using desktop experiments to perform a precise exploration of the parameters affecting buckling. We examine two separate modes of axial rotation: continuous rotation and oscillatory rotation. In each case, we demonstrate potential for significant increases in helical buckling length by a factor of as much as 5 within the parameter space studied and develop an understanding of the underlying mechanisms at play. In the case of continuous rotation, we compare our experimental results to theoretical predictions motivated by this work. The extensions in helical buckling length observed here suggest significant application to the problem of helical buckling in coiled tubing operations.