较低雷诺数下ITTC尺度效应换算方法的改进

Improvements of Scaling Method Recommended by ITTC at a Lower Reynolds Number Range

应用基于非结构化网格的过渡流模型,在商业CFD软件STAR-CCM+平台上,对不同雷诺数(Re)下螺旋桨模型和实桨进行数值模拟,分析了螺旋桨叶面和叶背边界层的流体流动随Re的变化情况,将浆叶0.75R剖面压力面和吸力面的摩擦阻力系数的数值模拟结果与国际船模试验池会议(ITTC)推荐的尺度效应换算公式以及平板摩擦阻力系数计算公式的计算结果进行对比,并对ITTC尺度效应换算方法在较低雷诺数下进行了改进,即应用不同的公式分别计算叶面和叶背的摩擦阻力系数.结果表明,螺旋桨叶面与叶背边界层的流体流动不同,故吸力面和压力面的摩擦阻力系数计算公式有所不同.当Re较小(接近临界雷诺数)时,改进方法比ITTC尺度效应换算方法计算的结果更准确;当Re>1.0×106时,改进方法与ITTC尺度效应换算方法的计算结果基本一致;当Re>2.0×106时,Re越大,2种方法的计算结果偏离实际值越多.

A transition model based on unstructured mesh was applied for simulation of the model and full scale propeller with varied Reynolds number(Re)on the commercial software STAR-CCM+platform.Changes of boundary-layer flow over blade face and blade back with Re were studied.Numerical results of friction coefficient of the 0.75 Rblade section were compared with those calculated by the ITTC formulas and the plate resistance formulas.The scaling method recommended by ITTC was improved at low Reynolds number range that two formulas were proposed for calculating viscous force coefficients of propeller blade face and blade back separately.Results show that the boundary-layer flow over blade face and blade back are different.Thus,different equations were needed to calculate the friction coefficients of suction side and pressure side of the blade section.Results show that when Reis small(close to the critical Re),results of the revised method are better than those of the ITTC method;when Re is greater than1.0×10^6,results by the two methods are basically the same;when Re continues to increase(greater than2.0×10^6),results calculated by the two methods both deviate from the actual value with the increase of Re.