Analysis of tunnel hydrodynamic characteristics for planing trimaran by model tests and numerical simulations

The planing trimaran hull has unique hydrodynamic performance due to the tunnel region. In this paper, results of experimental and numerical studies for the planing trimaran hull are presented to analyze the hydrodynamic characteristics of tunnel and its effect on the hull body. Model tests were carried out for volume based Froude number ranging from 0.90 to 5.87. Resistance, sinkage and trim angle obtained by towing tank show that the planing trimaran has poor resistance performance at the hump region, while it operates quite well in the planing mode. A three dimensional computational fluid dynamic (CFD) code based on the Finite Volume Method (FVM) was used to simulate the forward motion of the hull body with two degrees of freedom (heave and pitch) when Froude number is above 3.16. Calculated results were validated with the experimental data and showed good agreement. Wave profile, dynamic lift, longitudinal center of pressure and flow vectors in the tunnel region at various Froude numbers were provided to explain the hydrodynamic and aerodynamic mechanism of this region. At last, models with different tunnel height and beam were calculated to study the influence of tunnel configuration on hull behaviors and hydrodynamic performance.