Riser VIV suppression device tests for application to a southeast asia TLP

Abstract

The Southeast Asia metocean environment is characterized by moderate wind and waves with relatively strong and persistent currents. The design of a Tension Leg Platform (TLP) for Southeast Asia is strongly affected by the current and resulting drag loads, particularly if many risers are required. To reduce vortex-induced vibrations (VIV) of offshore tubular members i.e. top tension risers (TTRs), vortex suppression devices such as helical strakes and fairings are used. This paper gives an insight into a set of riser VIV model tests which is carried out to study the effectiveness of an open-back "U"-shaped fairing in suppressing riser VIV. The splitting loads and the drag loads of the fairings are also investigated during these tests. The tests are being done at the Marine Technology Center (MTC), Universiti Teknologi Malaysia (UTM) in support of this application, and also in part to increase local technological capabilities. Two sizes of risers are being tested in three configurations: (a) bare riser without any fairings; (b) riser with weathervaning fairings (normal condition) and (c) riser with fairings fixed at different headings (abnormal condition). The test results show that in the normal condition, the fairing is effective at suppressing VIV.