Abstract
In order to investigate the influence of ship airwake on aerodynamic characteristics of the carrier-based aircraft, UAV's landings in different winds over deck were simulated by Overset Mesh method. Firstly, mesh factors, steady and unsteady methods were compared based on single aircraft carrier. The results showed that the boundary layer mesh around ship didn't show obvious influence for our simulation, and the calculation results between the steady and unsteady time average showed a similar trend. Then, aircraft carrier's flow fields in three wind directions were analyzed, and ship airwake variations with different direction winds over deck were concluded as well. Next, the reliability of Overset Mesh was verified though single UAV's landing simulation. Finally, the coupled flow fields of UAV/ship were studied. The calculation results indicated that aircraft was always in a low dynamic pressure condition, the lift and pitching moment of UAV had apparent changes in landing. Meanwhile, the aerodynamic fluctuations of UAV also revealed differences in different wind directions. The simulation results can be regarded as a reference for the safety assessment of carrier-based aircraft's landing and its control in the future.
Highlights
Investigation of Ship Airwake and Rotor Aerodynamics Based on DES[ D]
In order to investigate the influence of ship airwake on aerodynamic characteristics of the carrier⁃based aircraft, UAV′s landings in different winds over deck were simulated by Overset Mesh method
Mesh fac⁃ tors, steady and unsteady methods were compared based on single aircraft carrier
Summary
采用无附面层的 435 万网格,基于定常收敛的 结果,然后进行非定常计算,比较 2 种计算状态下, 下滑线( 见图 1) 上的速度。 时间步长为 Δt = 0.005 s,每个时间步迭代 10 次。 取航母甲板尾部监视点 point⁃2( 见图 1) 的 y 方向速度收敛曲线如下所示: 从图 4 可以看出,从 t = 20.0 s 之后,Vy 呈现出 一定周期性的波动,流场进入非定常状态,而在 t = 4.0 s 之前速度波动不大。 取下滑线上不同时刻的 速度如图 5 所示。 可以看出,基于定常收敛的结果, 在非定常计算 t = 4.0 s 时间范围内,下滑线上速度 分布没有剧烈的变化,定常计算的结果与非定常时 均的结果差别不是很大,表明定常计算能反映出流 场的平均特性。 由于非定常时均计算非常耗时间, 因此,本文只对航母定常计算的流场进行分析,对其 时均特性进行了解。 结果,图 13c) 的展向升力分布也说明了这一点。 从图 13b) 可知, 无人机 开始为左侧滑, Cmx 为 - 15° 风向 时, 飞机侧滑角较大, 左右机翼不对 称性明显,如图 14c) 所示。 而随着靠近航母,左右 机翼的升力分布差别逐渐较小。 结合图 8c),由于 下滑线大部分处于上洗区,因此无人机的升力系数 比定常计算的值要大,这从图 14c) 也可以看出。 与 之前 2 种风向不同的是,在 x280 m 之前,下 滑线的上洗是不断增强的,但升力没有增加反而在 减小,需要进一步分析其原因。 3) 无人机的升力,俯仰力矩和滚装力矩受尾迹 影响较大。 0°风向和 15°风向时,随着下滑,无人机 的升力先变小再变大,飞机受下洗作用明显。 15°风 向时飞机对应的升力最大下降了 18%;而在-15°风 向时,无人机在穿越舰岛后方的分离区时,虽然存在 上洗,但由于顺风,随着靠近航母飞机的升力一直在 减小。
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