七叶大侧斜螺旋桨空泡特性及梢涡演化数值模拟研究

Numerical Simulation of a Seven-Blade Propeller with Skew on Its Cavitation Characteristics and Tip Vortex Evolution

关键词:  七叶螺旋桨  延迟分离涡模拟  空泡特性  梢涡演化  尾流场

Key words:  Seven blade propeller  Delayed detached-eddy simulation  Cavitation characteristics  Tip vortex revolution  Wake field

摘要:

为研究七叶大侧斜螺旋桨尾流场及梢涡特性，基于延迟分离涡方法（DDES）建立了螺旋桨空化流场数值预报模型，为验证所建立数值模型的准确性，进行了多套不同尺度网格的不确定性分析，同时将非定常流动中螺旋桨（VP1304）螺旋桨空泡及梢涡特性计算结果与试验结果进行了对比。基于该模型对七叶大侧斜螺旋桨的尾流场及梢涡特性进行了数值分析，计算结果表明：本文所建立的数值模型精度较高，可以准确地捕捉到梢涡空泡及梢涡尾流场特性；同时DDES方法相比RANS方法在对复杂湍流流动的捕捉能力更强，更适用于螺旋桨梢涡捕捉；尾流场网格加密对尾流场模拟及准确捕捉梢涡十分重要，但对螺旋桨水动力性能影响不大；尾流区域的轴向速度场可以分为加速流动区和自由流动区，进速系数越小，自由流动区与加速流动区之间的界限向外扩张越明显；E1619桨在重载工况有明显的梢涡空泡产生，而轻载工况空泡面积较小且无梢涡空泡发生；梢涡在向下游发展过程中会发生相互融合，进速系数越大，融合发生得越晚，梢涡强度也越小；七叶大侧斜螺旋桨在尾流区域会产生一个分支涡，分支涡起始于吸力弯曲面下缘，且与梢涡呈一定的夹角，进速系数越大，夹角越小。

Abstract:

A numerical simulation of cavitation field and tip vortex characteristics was conducted on a seven-blade propeller with skew using the numerical prediction model of propeller in cavitation flow based on the DDES（delayed detached-eddy simulation）. The uncertainty analyzing was conducted through a series of grids scale to verify the accuracy of the numerical model. The validation studies of the VP1304 propeller for unsteady cavitation flow and tip vortex characteristics are presented. Then the wake field and the tip vortex characteristics were simulated based on this method. The results indicate that the numerical model established has good accuracy， and is able to capture tip vortex cavitation and tip vortex wake field characteristics accurately.While compared with the RANS method， the DDES method was more capable of capturing complex turbulent flows， and was more suitable for propeller tip vortex capture. The refinement of the wake field has great influence for catching tip vortex， while it has only a slight effect on the thrust and torque of the propeller flow．The axial velocity distribution in the wake region is divided into accelerated flow region and free flow region．With the decrease of the advancement coefficient，the trend of the outward diffusion of the boundary line between this two regions is gradually enhanced. The E1619 propeller has obvious tip vortex cavitation under heave load conditions， while the cavity area was smaller and no tip vortex cavitation occurred under light load conditions. As the tip vortex developed downstream， the fusion between the tip vortexs would occur. As the advance coefficient increase， the later the fusion， the waker the intensity of the tip vortex is. The seven-blade with skew has branch vortex in the wake field， which start at the lower edge of the suction curved surface. There is a certain angle between the tip vortex and the brance vortex， and as the advance coefficient increase， the smaller the angle is.