Optimisation of fins on pipeline riser fairings using CFD

Pipeline risers are subject to vortex shedding in current flows and the resulting vortex induced vibrations (VIV) can be damaging.

Effective prevention of vortex shedding can be provided by a streamlined fairing, which has the added advantage of reducing drag loads.  The best performance is achieved when the fairing self aligns with the direction of flow and remains stable in that position. Fins, also called “fish tails”, can be placed on the pipeline riser fairing to ensure that the fairing aligns with the direction of flow and remains stable.

We investigated the self alignment behaviour of various fin configurations and performed analyses using the fluid-structure interaction module in Ansys CFX.  We investigated the effects of the fin shape and the flow Reynolds number. We recommended fin configurations that we optimised with respect to stability and drag over a range of Reynolds numbers.

As a result of our analysis, our client, CRP, avoided the expense of building prototypes and testing and gained a clear understanding of how and why the fin works.  We established  the sensitivity of the fin to parameter variations and developed optimised designs for a range of Reynolds numbers.