实尺度喷水推进船拖泵工况数值模拟与分析

Research on the pump towing drag of full scale waterjet ship with CFD

对于四泵推进的喷水推进船,在巡航工况时中间加速泵通常处于锁轴状态,其拖曳阻力的大小对喷水推进器的选型以及船泵机的最优匹配有着重要影响。然而,拖泵阻力很难通过船模试验的方法获得。为此,该研究在验证均匀和非均匀条件喷水推进器数值模型的准确性基础上,采用数值试验的方法对18节航速下某双泵推进喷水推进船的实尺度"船体+两台喷水推进器"系统带自由液面的流场进行了数值模拟,计算此时喷泵拖曳阻力及其所占船体阻力的百分比。以此喷泵拖曳阻力作为参考,对尺寸与上述喷水推进泵相近的某四泵推进喷水推进船的喷泵进行了选型和设计,并对该船在18节航速下加速泵拖曳阻力的大小进行了计算,进一步验证选型时拖曳阻力取值的合理性。为消除尺度效应的影响采用实尺度模型对"船体+四台喷水推进器"系统带自由液面的非定常流场进行计算,并探索了大尺度条件下船泵系统考虑自由液面和重力影响的非定常计算方法。

Accelerating pump towing drag of the ship propelled by four waterjet pumps at cruising condition has great influence on the process of waterjet selection and optimal match between hull, waterjets and the main engine. However, the pump towing drag is difficult to be obtained from the ship model test, and so far there is little record about the pump towing drag at home and abroad. For this reason, CFD method of waterjet in uniform and non-uniform flow were validated, and CFD method was used for the simulation of the viscous flow of the full scale ship propelled by two waterjets, and the pump towing drag and its percentage on the ship drag could be calculated. Taking this pump towing drag as a reference, the waterjet pumps of the ship propelled by four waterjet were selctected and designed. And then the towing drag of accelerating pumps of the ship could be calculated with CFD simulation, the results indicate that the percentage of the pump towing drag on the ship drag were roughly the same as hypothetical. In order to eliminate the scale effect, the method for calculating the unsteady viscous flow of full scale ‘hull + four waterjets' model with gravity and free surface was researched and introduced briefly.