The growing attention in reducing the risk of collisions or groundings during the approach to a harbour or while navigating in narrow fairways, makes the escort activities of paramount importance for a safe navigation in different scenarios. To this end, since early-design stage, Classification Societies prescribe to evaluate the maximum steering and braking force the tug is capable to provide. The analysis is usually performed adopting simplified methods, grouping all propulsive devices together to solve the equilibrium on horizontal plane. In this work, an advanced equilibrium resolution method is proposed considering each propulsive device as an independent actuator. This method allows to simulate the behaviour of a steerable thruster, by means of a 4-quadrant modelling of a ducted propeller, considering cross-flow effect as well. The adoption of such enhanced method makes the estimate of escort performances more reliable. To this aim, the performance prediction obtained with simplified and advanced method are here compared for a reference escort tug.

在减少驶入港口或在狭窄航道中航行时减少碰撞或着陆风险的日益关注，使得护航活动对于在不同情况下安全航行至关重要。为此，从设计初期开始，船级社规定要评估拖船能够提供的最大转向力和制动力。通常采用简化方法进行分析，将所有推进装置组合在一起以解决水平面上的平衡问题。在这项工作中，提出了一种先进的平衡分辨率方法，该方法将每个推进装置视为一个独立的致动器。该方法还可以通过对导管螺旋桨进行四象限建模来模拟可转向推进器的性能，同时还要考虑横流效应。这种增强方法的采用使得护送性能的估计更加可靠。为此，此处将通过简化和高级方法获得的性能预测值进行比较，以作为参考护航拖船。