海洋污损对叶切面性能影响的数值研究

通常情况下螺旋桨桨叶表面是抛光金属,没有涂装防污涂层,这使得桨叶表面易受污损的附着和侵蚀,然而污损对叶切面性能的影响却很少受到关注和研究。文章通过CFD方法对这种影响进行定量研究,并对产生影响的物理机制进行深入分析。采用SST k-ω湍流模型以NACA 4424翼型作为叶切面进行数值模拟,在海洋污损生物群落中选取藤壶作为桨叶污损对象,并在几何层面上直接进行建模。计算结果表明,污损会使得叶切面表面边界层分离更早,分离区域增大,这将显著降低叶剖面的升阻比C_L/C_D,进而导致螺旋桨推进效率大幅度减小。尽管如此,当污损高度超过一定值后,污损高度的增加对C_L/C_D的影响便会变得很小。数值计算与文献中试验结果吻合得较好。

Numerical Simulations of the Effects of Marine Fouling on the Hydrodynamic Performance of Blade Sections

Propeller blade surfaces are of polished metal and have no antifouling provision, which makes them vulnerable to biofouling. However, its effects on hydrodynamic characteristics of blade sections are rarely studied. The present work aims at quantifying the effects and providing a deep in-sight into the physical mechanism by means of Computational Fluid Dynamics (CFD). The simula-tion employs the SST k-ω turbulence model and is carried on NACA 4424 airfoils. Barnacles are se-lected as the study subject from the fouling community and are directly modeled at geometry level. The results of calculation show that the fouling causes earlier separation of boundary layers and in-creases separation region around airfoils, which leads to significant reduction of lift-drag ratio (CL/CD) and hence would result in remarkable decrease of propulsive efficiency of propellers. However, once the height of fouling exceeds a certain limit, the increase of the height has little effect on CL/CD. The results for CL/CDby numerical simulation agreed well with the experimental data in the literature.