Investigation of Interference Between Upstream and Downstream Cylinders in a Current for the HRTs and Jumpers With FPSO Application

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractExperiments and analyses have been made to determine the response of a downstream cylinder that is in the wake of a fixed upstream cylinder. This geometry is of great practical importance for risers in deepwater. It arises with jumpers in deepwater hybrid riser towers and in closely spaced risers. The theories of Huse [1], and Blevins [2] are applied to predict the steady response of the down stream cylinder. These predict that within the confines of the wake of the upstream cylinder, the drag on the downstream cylinder is reduced and there is a lift force that acts to draw the downstream cylinder into the wake of the upstream cylinder. There is apparently no simple, direct experimental confirmation of this predicted behavior.An experiment was made in the flow channel of the Scripps Institution of Oceanography to test these theories up to about 80 000 Reynolds number. The paper describes the methodology and results of these experiments to validate the parameters of the theoretical models.Preliminary measurements show that as the flow increases the downstream cylinder travels aft and inward towards the centerline of the wake.At small inline spacing the downstream cylinder moves upstream, implies negative lift, and impacts the fixed upstream cylinder.

Reliability assessment of the collision between marine risers

“…verifications by more experiments and is not available in the numerical tools wake field when the upstream riser was under VIVo This new model requires further non-negligible in the far wake (see Figure 2.17). Blevins and Wu (2007) put forward currently.…”