【作者】 王超；

【导师】 荣吉利；

【作者基本信息】 北京理工大学 ， 动力学与控制， 2016， 硕士

【摘要】 直升机的舰面起降,特别是在驱逐舰等中、小型舰船上起降,要比在地面执行同样飞行任务困难而且危险。由于舰船艉部流场中复杂的流动结构对直升机着舰过程中的操稳性能影响极大,严重威胁着直升机在舰面的安全起降。因此,开展舰船艉流场研究,分析其复杂流场的形成机理与流场结构,进而通过研究流场控制技术改善艉流场环境,提高舰载直升机舰面起降的安全性,是一项极具工程意义的工作。本文首先采用基于Spalart-Allmaras湍流模型的非定常脱体涡模拟(Detached-eddy Simulation,DES)方法对典型护卫舰船型进行数值模拟,一方面通过与试验数据对比发现,非定常计算结果与试验结果吻合度高,验证了本文采用的数值方法的可靠性。另一方面详细分析了舰船艉流场的形成机理以及其非定常特性,同时分析了舰岛建筑与机库门开合状态对艉流场的影响,研究发现机库上方建筑诱导的涡结构与机库边缘产生的涡结构会互相干扰,出现涡配对现象,从而形成新的涡结构。机库门开合状态对舰船艉部回流区范围的影响并不明显,但是当机库门半开时,艉部甲板上方远离机库门位置处的下洗湍动能最小。为了提高直升机舰面起降的安全性,采用主动控制技术改善艉部流场环境,模拟了不同吹/吸气组合条件对艉流场的影响,研究发现通过混合吹吸气方法,能有效的抑制艉流场的下洗速度,相比无控状态使得关键区域的下洗速度减小一倍,且能有效的控制回流区的中心位置和纵向长度,相比无控状态使得回流区的纵向范围减小25%,把回流区从艉部关键位置中移除。同时研究了不同机库截面外形与机库高度对艉部大分离流场的影响,结果表明,相比“凸”字形截面的机库外形,截面为“口”字形的机库不利于直升机的舰面安全起降,通过合理的降低机库高度可以有效的改善艉部飞行甲板处的起降环境。最后,本文初步推导了快速预测舰船艉流场回流区范围的计算公式。更多还原

【Abstract】 Helicopters’ landing on the frigate is more dangerous than the same situation on the ground,especially on the middle or small class frigates.Because of the complicated flow structures in the stern flow field of the ship,the stability of helicopter landing is greatly affected,which threatens the safety of helicopter seriously when taking-off and landing on the frigate.Therefore,the research on the frigate airwake is carried out to analyze the formation mechanism and complex flow field structure of the frigate airwake,and to improve the helicopter landing environment by studying the flow control technology,so as to improve the safety of the helicopters’ landing.The research can provide important reference for the engineering study.In this paper,the computational fluid dynamics software CFD++ is used to simulate the typical frigate using the Detached-eddy Simulation(DES)method based on the Spalart-Allmaras turbulence model.A comprehensive validation exercise has been performed by comparing with the experiment results,it is found that the velocity distribution of the steady-simulation results is quite different from the experiment results,however,the unsteady-simulation results agree well with the experiment results,which verifies the reliability and accuracy of the numerical simulate method adopted in this paper.Based on this,the formation mechanism and unsteady characteristics of the frigate airwake are analyzed in detail.At the same time,an analysis of the airwake flow topology at headwind condition highlights the vortex pairing process which dominates the flowfield above the deck.Additionally,the influence of hangar-door state(open,closed or half-open)on the airwake was also investigated in detail.It is found that the effect of hangar-door state on frigate airwake is not that obvious,except when hangar-door half opened the turbulence kinetic energy at the deck away from the hangar is the smallest.And simulations were made by adding blowing or suction devices on flight deck or hangar to alter the ship airwake for purpose of the improvement of safety when launching and recovering of helicopters to naval ships,the results showed that the flow control method can effectively control the region of recirculation zone and downwash velocity component.Meanwhile,the research on the characteristics of frigate ship airwake influenced by three different hanger shapes for a headwind and the Green 45° case is carried out.The results showed that equal height hangar shapes were not conducive to the safety when launching and recovering of helicopters to naval ships,compared by the same hanger height but with both lower sides.By reducing hangar height reasonably,the launching and recovering environment on flight deck could be improved.At last,the results verified the validity of the empirical equation for the prediction of the range of the recirculation zone.The empirical equation provide an important reference for the engineering study.更多还原