Bureau Veritas (BV) has authorized on an “Approval in Principle” basis a new Computational Fluid Dynamics (CFD)-based performance prediction methodology developed by Robert Allan Ltd. as the basis for formally granting the service notation Escort Tug.
While previously some classification societies have approved computer-based escort predictions for new tugs on a case by case basis, the majority still require a full-scale trial before issuing an escort notation and the associated escort numeral. The process of predicting steering and braking forces and assessing stability to meet classification society requirements has been notoriously complex and difficult without model tests or full scale trials. This is because the various forces from the hull, thrusters and towline during escort operations all have to be determined, along with the equilibrium yaw and heel orientations of the tug under all the operating conditions of interest.
Now, this new CFD option is available for the tug owner, without the delays and expense of model tests or the cost, complexity and inherent potential inaccuracy of full-scale sea trials. By applying sophisticated CFD techniques within a preapproved, standardized methodology, Robert Allan Ltd. is able to accurately evaluate escort performance and compliance with Class requirements early in the design process. Applicable not only to in-house designs, Robert Allan Ltd. offers this CFD Escort Analysis as a service to clients interested in evaluating existing tugs or other designs.
While BV is the first major Classification Society to formally grant an Approval in Principle for this advanced methodology, Robert Allan Ltd. is actively working with other IACS members to obtain their approval of this CFD based methodology.