FIV2018 Paper Management System, FIV2018 Conference

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The Pinning Force To Prevent In-Plane Fluid Elastic Instability
Ryoichi Kawakami

Last modified: 2018-06-20


The in-plane (stream-wise) fluid elastic instability of triangular tube arrays caused tube-to-tube wear indications observed in U-bend regions of tube bundles of San Onofre  Unit-3 steam generators. In the U-bend region of steam generators, flat bar type tube supports (e.g. Anti-Vibration Bars:AVB) have not been designed to support tubes in the in-plane directions. In order to prevent the in-plane fluid elastic instability, U-bend tubes have to be supported in the in-plane direction or support structures have to generate sufficient damping against in-plane motion.

To support and pin a tube at an AVB in the in-plane direction, the contact force pressing the tube against the AVB must be sufficient to overcome both the out-of-plane fluid forces acting to lift the tube off the AVB’s surface and the in-plane fluid forces acting to slide the tube along the surface of the AVB. This paper defines the pinning force at a tube-to-AVB intersection is the tube-to-AVB contact force necessary to prevent tube lift-off and sliding and  demonstrates calculation methods of the pinning force compared with a full scale single-tube mockup test results.


Fluid elastic instability; tube bundles

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