Strake systems and methods

Abstract

There is disclosed a system comprising a structural element, at least one helical strake about the structural element, and at least one ramp to provide a transition from the structural element to the helical strake.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims priority to U.S. Provisional Application 60 / 713,981 filed on Sep. 2, 2005, herein incorporated by reference in its entirety.FIELD OF INVENTION [0002] The present disclosure relates to strake systems and methods. BACKGROUND [0003] Structural elements can be installed at sea from a floating vessel using a J-lay configuration where the structural element is held vertically on the vessel and dropped vertically into the water and then when it reaches the bottom of the body of water, it lays horizontal, or alternatively structural elements can be installed in a S-lay configuration where the structural element is held horizontally on the vessel, drops to vertical through the body of water, and then rests on the bottom of the body of water in a horizontal configuration. Other configurations for installing a structural element from a vessel in a body of water are also known. [0004] Referring now to FIG. 1, system 100 for i...

AI Technical Summary

Benefits of technology

[0021] improved methods of installing strake elements for suppressing vibration in a flowing fluid environment on a structural element before the structural element is installed in the flowing fluid environment which does not require intervention or adjustment of the strake elements once the structural element is in the flowing fluid environment.

Problems solved by technology

These vibrations may be caused by oscillating dynamic forces on the surface which can cause substantial vibrations of the structural element, especially if the forcing frequency is at or near a structural natural frequency.

The vibrations may be larger in the transverse (to flow) direction; however, in-line vibrations can also cause stresses, which may sometimes be larger than those in the transverse direction.

If the frequency of this harmonic load is near the resonant frequency of the structural element, large vibrations transverse to the current can occur.

These vibrations can, depending on the stiffness and the strength of the structural element and any welds, lead to unacceptably short fatigue lives.

In fact, stresses caused by high current conditions in marine environments have been known to cause structural elements such as risers to break apart and fall to the ocean floor.

For instance, a riser pipe that is vibrating due to vortex shedding will disrupt the flow of water around it more than a stationary riser.

This may result in more energy transfer from the current to the riser, and hence more drag.

A pre-installed strake may be damaged if it passes over the stinger.

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