Comprehensive Riser VIV Model Tests in Uniform and Sheared Flow

Abstract

Despite of considerable research activity during the last decades considerable uncertainties still remain in prediction of Vortex Induced Vibrations (VIV) of risers. Model tests of risers subjected to current have been shown to be a useful method for investigation of the VIV behavior of risers with and without suppression devices. In order to get further insight on VIV of risers, an extensive hydrodynamic test program of riser models subjected to vortex-induced vibrations was undertaken during the winter 2010 by Shell Oil Company. The VIV-model test campaign was performed in the MARINTEK Offshore Basin Laboratory. A new test rig was constructed and showed to give good test conditions. Three different 38m long riser models were towed horizontally at different speeds, simulating uniform and linearly varying sheared current. Measurements were made In-Line (IL) and Cross-Flow (CF) of micro bending strains and accelerations along the risers. The test program compromised about 400 tests, which give a rich test material for further studies. In the present paper the test set-up and program are presented and selected results are reported.