What is VIV? • VIV is oscillation of a body produced by fluid

flow.

• Movement can be 1D, 2D, or a complex 3 dimensional pattern (see trajectories below)

Acknowledgments This work is supported in part by the National Science Foundation under NSF award number 1460461. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect those of the National Science Foundation.

The University of Massachusetts College of Engineering and the Fluid-Structure Interactions Laboratory.

Special thanks to Daniel Carlson and Yahya Modarres-Sadeghi, my daily mentors and teachers, and Banafsheh Seyed-Aghazadeh, whose paper and computer programs about MAC were the starting point for this project.

Poster Template copyright Colin Purrington

Experimental Set-up

Nicholas Capell, Daniel W. Carlson, Banafsheh Seyed-Aghazadeh, Yahya Modarres-Sadeghi

Notes and Citations https://en.wikipedia.org/wiki/Karman_vortex_street

Jain, Anil, Yahya Modarres-Sadeghi. (2013). Vortex-induced vibrations of a flexibly-mounted inclined cylinder. Journal of Fluids and Structures, 43. Retrieved from www.elsevier.com/locate/jfs

Bearman, P. W. (1984). Vortex shedding from oscillating bluff bodies. Annual Review of Fluid Mechanics, 16. Retrieved from http://www.annualreviews.org/doi/abs/10.1146/annurev.fl.16.010184.001211.

Banafsheh Seyed-Aghazadeh and Yahya Modarres-Sadeghi. (Unpublished Paper). Reconstructing Vortex-Induced-Vibration Response of Flexible Cylinders Using Limited Localized Measurement Points.

Purpose of this study •  VIV of flexible cylinders normal to the flow has

been studied extensively. Inclined cylinders have not.

•  The independence principal: current understanding of inclined cylinders proposes that they behave like vertical ones if only the velocity normal to the cylinder is considered. This is problematic for steeper angles.

•  This experiment will illuminate the behavior of VIV in flexible cylinders over a 180 degree range without the independence principal.

•  Modal Assurance Criteria (MAC) is a mathematical method for reconstructing the mode shapes and displacements of the complete cylinder from limited data points.

•  Demonstrating MAC’s effectiveness will guide future studies with limited available data and could be a method for extrapolating conclusions where exhaustive data is too expensive to collect.

Goals and Procedures for Summer 2015 •  To collect video of all angles and relevant velocities. •  To collect data using Cabrillo Tracker video tracking software for ten points per velocity per

camera angle (60°, -70°, -80° complete) •  To ensure the data was complete, synchronous, and reasonable.

Vortices are shed downstream

Applications

Power lines

•  A hollow rubber cylinder marked with dots at half-inch increments

•  Cylinder mounted rigidly at both ends

•  Cylinder’s submerged length, total length, and tension (at rest) held constant for all angles and velocities

•  Two high-speed cameras to capture the cylinder’s motion from two angles

•  Flow velocities of .064 to 0.25 m/s at .013 m/s increments

•  Angles of ±80°, 70°, 60°, 45°, 30°, 15°, and 0° (vertical).

Case Study Angle: 60° Flow Velocity: 0.24 m/s

Data check: if the data is synchronous (i.e. usable) the crests and troughs from both lines should line up.

Note that the frequency of the normal, in-line vibrations is twice that of the cross-flow. Graphs from the MAC code reflect this.

Trajectories of positions 5-13 on planes normal to the cylinder. One important conclusion of this study will be the direction of these paths.

Suspension bridges

Floating Wind Turbines

Flow creates vortices as it moves past the cylinder

Vortices are low-pressure regions; the cylinder moves into these regions.

MAC results: The figure on the left shows snapshots of the in-line cylinder shape through time, which displays a marked tendency toward the second mode shape in this case. The figure on the right shows the effectiveness of the MAC projection. The red dots are the root mean squared (RMS) values for the amplitude of tracked positions along the cylinder’s length. The blue line is the MAC projection of the RMS values along the cylinder’s entire length. In this case the MAC projection fits the experimental data well.

Fluid flow

RM

S of

dis

plac

emen

t

Length of Cylinder (Normalized)