超音速、高超音速有攻角的三维薄翼非定常二次理论及其应用

 动导数对于飞行器的动态品质分析和控制系统的设计是必不可少的参数,它直接影响飞行器的动态特性。因此,国外自七十年代以来,无论在风洞实验、飞行试验,还是分析、计算等方面都作了很多工作,取得了较大的进展。 动导数计算说到底主要是非定常气动力计算问题,已有的线化理论不能满足需要,对考虑非线性效应的动导数计算方法的需求则日显迫切。二次理论是计算非线性效应的一种方法,它是由第二次叠代或物面偏角参数的二次展开法构成,主要非线性效应由二次方程算出。

A SECOND-ORDER THEORY FOR THREE-DIMENSIONAL UNSTEADY FLOWS AND ITS APPLICATION TO THIN WINGS WITH ANGLE OF ATTACK AT SUPERSONIC AND HYPE-RSONIC SPEEDS

According to the assumption of high Mach numbers the secondorder equation for unsteady flow reduces to a form analogous to that for steady flow. As an approximation, a particular solution is derived from the assumption of local two-dimensionality instead of the approximate three-dimensional particular solution.In treatment of the unsteady problem for delta wings with low, aspect ratio and supersonic leading edges, the non-linear pressure relation and the modified reference flow parameters are adopted to take the effect of mean angles of attack into account. Analytical expressions are obtained for the first order expansion of the unsteady velocity potential. They conduce to simplifying the calculation of stability derivatives to a great extent.Stability derivatives for flat .plate, double-wedge or biconvex delta wings oscillating at low frequencies are given respectively. Since the corresponding experimental data are unavailable, the obtained results, are merely compared with those of Hui's flat plate1"4'1, and both results are in good agreement.