基于主动射流方法的椭圆水翼梢涡空化抑制研究

Suppression of tip vortex cavitation of elliptical hydrofoil based on active water injection methods

[目的]梢涡空化会产生压力波动和流动噪声,预测梢涡空化的初生和发展过程,了解其作用机理并加以抑制是船舶螺旋桨与旋转机械亟待解决的问题。[方法]以剖面为NACA 0012翼型的椭圆水翼为研究对象,基于IDDES湍流模型和Schnerr-Sauer空化模型,分别在全湿流和空泡流两种工况下对水翼梢涡及其空化现象进行模拟,分析水翼梢涡及其空化之间的相互作用特性。进一步,通过主动射流方法控制水翼梢涡空化,并对比两种开孔射流方式,即垂向射流和侧向射流的作用效果。[结果]以梢涡体积作为空泡抑制的判断标准,与无射流工况对比,垂向射流工况对空泡的抑制效果可达到8.09%;而在侧向射流工况下,射流对空泡的抑制效果更加明显,达到了10.47%。结果证明两种主动射流方式均可以有效抑制梢涡空化。[结论]通过机理分析发现,垂向射流会影响水翼梢涡入射流的流速及流向,提高梢涡湍动能的耗散项,从而降低水翼的梢涡强度;而在侧向射流工况下,射流则直接作用于梢涡,所携带的能量极大地破坏了水翼的梢涡结构,从而大大降低了梢涡空化现象的产生。

[Objective]As tip vortex cavitation(TVC)causes noise radiation and vibration,it is necessary to understand how to predict and control its development,and understand its mechanism in order to suppress it,especially in the field of ship propellers and other rotating machinery.[Method]Focusing on an elliptical hydrofoil with an NACA 0012 cross-section,this study uses the Improved Delayed Detached Eddy Simulation(IDDES)turbulence modeling method and Schnerr-Sauer cavitation model to simulate TVC on the hydrofoil and analyze its behavioral characteristics under wet flow and cavitation flow conditions.After that,two active water injection methods,side injection and top injection,are introduced into the simulation to reduce and sup-press cavitation inception respectively.[Results]Taking the cavity volume of the tip vortex as the criterion for cavitation suppression,compared with the condition without water injection,top injection can inhibit cavit-ation by 8.09%.Moreover,under the condition of side injection,the effect of the injecting flow on the cavita-tion is more obvious,reaching 10.47%.The results show that both top and side injection can effectively sup-press TVC.[Conclusion]Top injection can change the flow direction and speed of the tip vortex incident flow,and increase the dissipation term of the turbulent kinetic energy;while in side injection,the energy it car-ries acts directly on the vortex structure of the hydrofoil,destroying the vortex and greatly suppressing the gen-eration of cavitation.