Study on the effect of near-wall grid on numerical prediction of resistance for planing trimaran

A near-wall grid is a critical factor affecting the accuracy of numerical predictions for planing trimarans (double tunnel-planing boats). This study utilizes STARCCM + to investigate the influence of dimensionless near-wall first-layer grid thickness (y+1 ) on the numerical simulation of the resistance of planing trimarans. By comparing the computational fluid dynamics results with experimental values, the variation in y+1 is found to have a significant impact on the numerical simulation of the resistance of planing trimarans; as the sailing speed increases, the optimal y+1 value decreases. In this study, the changes in the flow field of a planing trimaran are analyzed. The air flow obstruction caused by the front part of the tunnel is observed to intensify with increasing y+1 . Consequently, the pressure resistance between the front and rear of the tunnel increases. Furthermore, the increase in y+1 hinders the flow separation at the step, leading to an increase in the wetted area of the step's aft portion; consequently, the resistance calculated in the simulation increases. This study provides a reference for the selection of y+1 for planing trimarans, thereby reducing the time apportioned to mesh independence testing.