5th Computational Methods and Ocean Technology (COTech 2026)

Anti-phase vortex shedding behind dual step cylinders

Not scheduled

20m

KE E-102 (University of Stavanger, Norway)

Plenary Contribution Advanced Computational Methods & Applications in Marine, Subsea and Offshore Technology

Speaker

Lars Erik Holmedal (Department of Marine Technology, NTNU)

Description

Vortex shedding behind stepped cylindrical structures can exhibit complex threedimensional
wake dynamics due to the interaction between vortex cells generated by
different cylinder segments. In the present study, a numerical study is conducted
to investigate the flow past dual step cylinders at ReD = 150 with a low diameter
ratio D/d = 1.33 and three aspect ratios L/D = 1, 3, and 6. Particular attention
is paid to the case of L/D = 3, where the vortex shedding behind the two smallcylinder
segments undergoes a transition from an initial in-phase state to a stable
anti-phase state. The transition is characterized by the gradual evolution of the phase
relationship between the vortex shedding from the two small-cylinder segments. The
wake with anti-phase shedding is characterized by consecutive vortex dislocations
occurring alternately at the two boundaries between adjacent vortex cells.. These
observations provide further insight into the complex vortex dynamics associated
with geometrical discontinuities in cylindrical marine structures and contribute to a
better understanding of wake interactions relevant to marine and offshore engineering
applications.