A Study On The Aerodynamics Drag Optimization Of The High-speed Trimaran Planing Craft

The high-speed trimaran planing crafts,whose navigation speed is greater than 60 knots,is a kind of newly developed high performance vessels with excellent speediness and exercise performance.And It has been widely used in military and civil fields.Traditionally,the study of high-speed trimaran planing crafts mainly focuses on the hydrodynamic performance,few attention has been paid to its aerodynamic performance.The main reason is that when the speed is low the aerodynamic resistance is far less than the hydrodynamic resistance.But a study shows that the aerodynamic drag of the high-speed planing crafts could be over 10% of the total resistance when navigation speed is greater than 60 knots,which suggests that the aerodynamics of the planing crafts and its influence should not be neglected.First of all,based on Star CCM+ software platform,numerical simulation of aerodynamic drag performance of a high-speed trimaran planing crafts was carried out by using the Realizable-K – ω turbulence model.On this basis,a set of stern shapes of the planing crafts are designed for the purposes of controlling the air flow surrounding the high-speed trimaran planing crafts then evaluate their aerodynamic performance.And choose the scheme that the aerodynamic resistance is lower than the original ship as an alternative.Then,the wind tunnel test is carried out to verify the aerodynamic resistance performance of the alternatives.The numerical simulation model is improved on the basis of wind tunnel test,then a high precision aerodynamic numerical simulation method of high-speed trimaran planing crafts is obtained.The numerical simulation results are compared with the wind tunnel test results,and the error is less than 5%.Based on this method,the aerodynamic flow field of a high-speed trimaran planing crafts is analyzed,the characteristics of rear airflow and the aerodynamic drag reduction mechanism is obtained.Finally,based on the above research,three key design parameters for changing the stern shape are obtained.Three design parameters are optimized by Numerical Simulation Based Design technology combined with NSGA-II optimization algorithm,aims at the minimum aerodynamic drag.Relationships between aerodynamic drag and key parameters are studied,and an optimization of the high-speed trimaran planing crafts stern shape is obtained.The aerodynamic drag reduction effect of the optimized scheme is verified by analyzing the aerodynamic flow field of the optimal scheme.The final results show that,at designed speed,the aerodynamic drag of high-speed trimaran planing crafts reduced 34% to 40% after the planing crafts stern shape were optimization.