Passive shock wave/boundary layer control of wing at transonic speeds

At supercritical conditions a porous strip （or slot strip） placed beneath a shock wave can reduce the drag by a weaker lambda shock system, and increase the buffet boundary, even may increase the lift. Passive shock wave/boundary layer control （PSBC） for drag reduction was conducted by SC（2）-0714 supercritical wing, with emphases on parameter of porous/slot and bump, such as porous distribution, hole diameter, cavity depth, porous direction and so on. A sequential quadratic programming （SQP） optimization method coupled with ad]oint method was adopted to achieve the optimized shape and position of the bumps. Computational fluid dynamics （CFD）, force test and oil test with half model all indicate that PSBC with porous, slot and bump generally reduce the drag by weaker lambda shock at supercritical conditions. According to wind tunnel test results for angle of attack of 2° at Mach number M = 0.8, the porous configuration with 6.21% porosity results in a drag reduction of 0.0002 and lift-drag ratio increase of 0.2, the small bump configuration results in a drag reduction of 0.0007 and lift-drag ratio increase of 0.3. Bump normally reduce drag at design point with shock wave position being accurately computed. If bump diverges from the position of shock wave, drag will not be easily reduced.

考虑吸波材料的雷达散射截面伴随优化方法

反隐身技术的发展对军用飞行器的隐身性能提出更高要求,针对考虑吸波材料的飞行器低雷达散射截面(RCS)设计问题,结合阻抗边界条件,建立了考虑吸波材料的麦克斯韦方程离散伴随方程,推导了伴随方程的多层快速多极子展开形式,实现了RCS关于外形、材料电参数、涂覆厚度等参数的高效、高精度梯度求解。提出一种基于开关函数的吸波材料涂覆位置优化方法,采用进气道等典型外形对几何外形、材料涂覆位置、涂敷厚度、电磁参数等设计变量开展优化设计。设计结果表明,考虑吸波材料特性的伴随优化方法可以在理想导体外形设计和材料涂敷的基础上进一步减缩散射强度,同时能够实现对材料参数、涂覆厚度的优化设计,为吸波材料的选择和涂覆提供指导;基于开关函数的涂覆位置优化能够在材料总重量的约束下,实现吸波材料的最优分配。提出的吸波材料的RCS伴随优化方法可以为吸波材料高效涂敷方案设计提供参考和技术支撑。