Research On Drag And Flow Field Characteristics Of Trimaran Based On Numerical Simulation

As a kind of high-performance ship type,trimaran exhibits excellent resistance performance at high speeds.Due to its special structure,there are complicated interferences between different hulls during sailing,which makes it difficult to study the flow field interference between hulls and their effects.At the same time,when the classic real ship forecast conversion method is applied to the trimaran,the difference in Reynolds number caused by the difference of the side hull and the main hull size is ignored,which will also bring certain errors.Therefore,this paper studies and analyzes the conversion method of flow field specificity and real ship resistance of a square-tail trimaran.For this type of trimaran,comprehensive research and analysis are carried out by combining ship model tests and numerical simulation calculations.First,conduct resistance tests on three trimaran models with different scale ratios to obtain relevant data.On this basis,the numerical simulation program is explored and verified.Then add the numerical calculations at the real ship scale and the smaller scale to explore the difference in resistance and flow field characteristics when the scale of the smaller model is gradually increased to the real ship scale,and analyze the scale effect in the conversion results of the real ship resistance of the trimaran Related factors such as flow field.And according to the results of the Reynolds number and frictional resistance coefficient related to the flow regime near the boundary layer,the correlation and specificity of the two in the trimaran are analyzed,and finally,a revised idea for the conversion method of the trimaran’s real ship resistance is provided.The research results show that compared with the monohull,the wave interference between the hulls of the trimaran is more severe when sailing at high speed.As the speed increases,the wave making of the hull shrinks to the midship longitudinal section,and the position of the side hull has a tendency to move backwards.At low speeds,there are fluid clusters with opposite vertical velocities near the side bodies,forming a swirling streamline structure,and the side bodies cut them into smaller swirling structures and make their transformation disappear after the speed gradually increases.And this phenomenon gradually weakens with the increase of the scale of the trimaran ship model,and the scale effect phenomenon caused by this flow field is finally manifested as a significant difference between the resistance conversion result at the too small scale and the larger scale result.When the Reynolds number of the main hull is in the range of complete turbulence,the friction drag coefficient of the trimaran is slightly larger than that of the main hull due to the presence of the side hull,and the results are in good agreement with the empirical formula.When the main hull is in complete turbulence and the side hull is in a transitional state,the results of the trimaran are located on the upper and lower sides of the formula result,and the larger scale result is on the upper side.It shows that within a certain range of Reynolds number,the turbulence state of the side hull has a very important influence on the drag results of the trimaran.