VIV Fatigue Assessment by Extended Scaling of Model Test Results

Abstract

A method is proposed for VIV fatigue assessment of pipeline spans and risers by direct scaling of model test results.  Scaling approximations serve to extend the range of applicability of a limited number of VIV test data.  Also, scaling is applied only for the dynamic portion of the response, with the static portion calculated by analysis, which then provides the conditions for scaling.  Ultimately using the basic and extended scaling approximations described, the problem of a simply supported span, on uniform pipe subject to constant current velocity is approximately characterized by a single dimensionless parameter.  As a result, for any (“prototype”) span to be assessed, any VIV test with similar end conditions (e.g. simply supported) can be scaled to yield the prototype current velocity for which similarity is satisfied.  To facilitate this, test data from recent, well-instrumented VIV tests on simply supported spans are processed yielding convenient and physically meaningful normalized parameters describing the test conditions and response.  Fatigue damage rates from the scaling method are compared to those from  the DNVGL-recommended assessment procedure and those from the frequency domain version of Vivana.