基于计算流体力学的配对进近尾流安全间隔研究

Study on wake safety intervals of PA based on CFD

为解决多变环境条件下通过单纯数学建模方法预测尾流存在精度不足的问题,首先,研究近距平行跑(CSPRs)道配对进近(PA)模式尾流安全区的基本要求;然后,通过建立运输机机翼尾涡流场,采用k-ε模型数值模拟计算侧风影响下的翼尖涡涡量场,得到配对前机尾涡空间分布特征,分析PA尾流安全区,提出基于计算流体力学(CFD)的PA尾流安全间隔计算方法;最后,以上海虹桥机场为例,采用数值模拟方法计算配对前后机分别为B747-400和B737-800,侧风风速3 m/s时的情况,验证该方法的科学性和有效性。结果表明:侧风可以加剧尾流的横向位移,配对后机可在配对前机上风方向跟进飞行避开尾流影响;当飞行环境一定时,前机翼展是PA最大尾流安全间隔值的决定性因素;基于CFD的PA尾流安全间隔计算结果能较好地拟合试验测量值,提高PA尾流安全间隔值的计算精确性;相同配对机型条件下,基于CFD的PA尾流安全间隔计算结果远小于现行尾流间隔标准。

In order to address the lack of accuracy in wake prediction by simple mathematical modeling method under changeable environment,firstly,basic requirements of wake safety zones in PA mode for CSPRs were studied.Secondly,wingtip vortex under influence of crosswind was numerically simulated by adopting k-epsilon model in a vortex field created at the tail of transport wing,and spatial distribution of wake vortices before pairing was obtained.Then,a calculation method of PA wake safety intervals was put forward based on CFD after analyzing PA wake safety zones.Finally,with Shanghai Hongqiao Airport as an example,numerical simulation was conducted for a case where lead aircraft and trail aircraft were B747-400 and B737-800 respectively under crosswind of 3 m/s to verify the proposed method in terms of scientificity and effectiveness.The results show that crosswind can intensify transverse displacement of wakes,and trail aircraft can follow up flight in upwind direction of lead aircraft so as to avoid influence of wakes.When flight environment is constant,lead aircraft's wingspan is the decisive factor for maximum wake safety interval of PA.It is also found that the calculation results of safety intervals based on CFD can better fit experimental measured values,thus improving calculation accuracy.Moreover,CFD-based results are far less than current wake interval standard under the condition of same paired types.