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利用计算流体力学(CFD)方法预测阻力是飞行器气动设计中的关键环节。采用广义Richardson外插方法分别对数值方法预测二维简单构型的压差阻力、摩擦阻力和三维复杂构型的总阻力的精度进行了分析。在NACA 0012翼型无黏绕流和平板湍流边界层两个算例中验证了NSAWET程序和广义Richardson外插方法,分别得到数值算法预测压差阻力和摩擦阻力能达到的名义精度。进而模拟三维通用研究模型(CRM)翼身组合体绕流,得到的阻力名义精确值在DPW 5的统计误差带范围之内;综合DPW 5的计算结果来看,不同CFD解算器的结果之间存在一定差别,阻力预测精度总体上不符合二阶。可见,标准Richardson方法采用的二阶精度假设难以普遍适用,有必要采用广义Richardson外插方法得到名义精度。针对不合理的名义精度,采用Roache建议的方法加以限制。广义Richardson外插方法有助于提高误差分析的合理性,可以进一步降低网格对阻力预测的影响。
Predicting the resistance using computational fluid dynamics (CFD) is a key aspect in the aerodynamic design of aircraft. The generalized Richardson extrapolation method is used to analyze the accuracy of the numerical method for predicting the pressure drop resistance, the frictional resistance and the total drag of the two-dimensional simple configuration respectively. NSAWET program and generalized Richardson extrapolation method are validated in two examples of NACA 0012 airfoil non-viscous flow and flat turbulent boundary layer. Numerical algorithms are used to predict the nominal accuracy which can be achieved by differential pressure resistance and frictional resistance respectively. And then the three-dimensional universal model (CRM) wing-body assembly flow is simulated. The nominal value of resistance obtained is within the statistical error band of DPW 5. Based on the calculation results of DPW 5, the results of different CFD solvers There is a certain difference between the resistance prediction accuracy generally does not meet the second order. It can be seen that the second-order precision assumption adopted by the standard Richardson method is not universally applicable, and it is necessary to obtain the nominal accuracy using the generalized Richardson extrapolation method. For unjustified nominal accuracy, use the suggested method by Roache to limit it. The generalized Richardson extrapolation method can improve the rationality of error analysis and further reduce the effect of grid on the prediction of resistance.