Dynamic simulation of subsea pipeline and trawl board pull-over interaction

• A novel computational strategy for trawl gear and pipeline interference is proposed.
• We address in detail a 6 DOF description of the trawl board hydrodynamic loads.
• Agreement between numerical and experimental results is demonstrated.
• Sensitivity of parameters important for prediction of design loads is quantified.

This paper presents a novel strategy based on the finite element method for prediction of fishing gear interference loads on subsea pipelines. Trawl board pull-over interaction is addressed with emphasis on hydrodynamic load representation, handling of pipe-trawl contact and modeling of the trawl gear system. A validation study involving 34 model test runs was carried out for three trawl boards with variation of pipe span height, towing velocity, towing line stiffness and pipe support conditions. The simulated bias of the load impulse was found to be within a 10% margin of the model test measurements. Based on the validated numerical model a sensitivity analysis involving nearly 250 simulations was conducted. The interaction behavior was seen to be greatly influenced by the board-pipe friction coefficient, the tension level in the wire between board and trawl net, the towing line drag properties and the direction of over-trawling.