Bumper

The bumper element model is used to model contact force between a body and a globally fixed cursor or bumper, or contact forces between bodies:

The model is particularly useful in the analysis of offshore installation operations, where deflectors / bumper bars are used to guide a module to its correct position and to protect existing equipment from impact damages.

The bumper element model defines a pair of lines (i.e. bumper bars) with specified location and length. Assuming that one line is fixed to a body, the other line can either be fixed to another body or have a globally fixed location. The contact force between the lines (i.e. cylinder bars) is defined through a specified distance / force relation, which can be non-linear and include damping. However, sliding friction between the bumper bars is not included.

bq.. Notice: If the centre line of one cylinder approaches the other cylinder along the centreline of the latter (see Figure), the force specified for zero distance will be turned on at contact between centre lines. This will give a large transient force, and unintended numerical problems. Make thus sure that the bumper cylinders are long enough to avoid end contact.