Characterizing the dynamics of a flexible rod wrapped by transverse repeated ribs subjected to axial flow

• The dynamic instability of a repeated ribs cylindrical rod in annular axial flow geometry was studied.
• The results indicate a strong dependency between rod instability and rib roughness.
• The rod dynamics become stabilized when the pitch-to-height ratio of the ribs increases.
• Increase of the rib width-to-height ratio destabilizes the rod.
• The nonlinear model confirms the existence of post critical instability and the reliability of the linear results.

This study focuses on the dynamics of a flexible cylindrical structure wrapped by repeated transverse rectangular ribs, in an annular flow geometry, under two boundary conditions: simply supported ends and clamped ends. The dynamics is predicted by linear and nonlinear theories. Based on the linear equation a straightforward nonlinear equation can be derived. A parametric investigation of the effect of the ribs’ dimensionless geometry characterized by the pitch-to-height and width-to-height ratios, on the fluid-elastic instability characteristics is considered. The results of the present study indicate a strong dependency between rod instability and rib roughness. The nonlinear model confirms the existence of post critical instability and the reliability of the linear results.