【作者】 李鹏；

【导师】 张桂勇；

【作者基本信息】 大连理工大学 ， 船舶与海洋结构物设计制造， 2024， 硕士

【摘要】 水上飞行器如水上飞机、地效翼飞行器等,由于其两栖特性、快速性、长续航性的特点,在民用以及军用方面有着很大发展空间。水上飞行器的发展有着如下必须解决的问题:提升运载能力、增强安全性及提高其在波浪中行驶的姿态稳定性以及抗浪冲击能力,因此地效飞行器和水陆两栖飞机的发展势必要向大型化方向迈进。然而,大型化便意味着它们在水面降落阶段会承受巨大的冲击力,这对船体结构的稳定性和安全性构成了严峻挑战。意味着需要针对此类水上飞行器的着水过程进行评估并且提出降低其着水过程砰击载荷以及增强其姿态稳定性的方式方法。首先,本文借助STAR-CCM+软件进行了数值模拟分析,并通过楔形体入水实验和参照NACA TN 2929 A模型的着水实验验证了模拟结果的准确性。研究了NACA实验室设计的可以满足飞行器降载增稳效果的双板式水橇在不同长宽比、静载荷系数和底升角条件下的降载性能表现。研究发现,双板式水橇通过将飞机水面降落时的一次接触分解为两次接触,有效降低了峰值垂向载荷,而这一效果可通过合理调整水橇各项参数得以实现。总体而言,静载荷系数在20至60间较为理想,既能避免因过小而导致显著冲击载荷,又能防止因过大而缩减水橇尺寸、削弱其降载能力。水橇的长宽比同样需控制在1至3的范围内,以保证合适的接触面积及有效的降载效果。此外,底升角应保持在0°至4.5°,以恰当调节水橇在水平和垂直方向的投影面积,降低接触水面时的冲击力和俯仰力矩,从而抑制飞机腹部中后部接触水面瞬间产生的垂向载荷及稳定飞机着水过程中的飞行姿态。水橇的安装位置也至关重要,建议将其设置在距飞机重心前后0-0.03倍飞机长度的位置,以确保在水上降落时有效地控制飞机姿态和降低载荷。其次,根据上述研究得到的水橇各个参数的建议范围,使用DOE、BP神经网络与MIGA结合的方法进行水橇参数优化。将得到的参数组合反归一化后得到最优个体的水橇形状参数及其安装位置,经验证加装该优化型号水橇的飞机模型着水过程中的垂向载荷相对于原模型以及普通水橇均大幅降低,降载幅度在51.6%左右,且姿态稳定性大幅增加,增加幅度在90.9%。随后,针上述优化得到的双板式水橇的相对最优形式,利用STAR-CCM+软件进行了数值模拟仿真,研究了飞行器于不同浪向以及不同降落位置着水过程中载荷的变化规律以及不同工况对优化所得水橇降载效果的影响规律。研究揭示了水橇通过将飞机触水过程转化为两次接触以减轻垂向载荷峰值,通过调节水橇参数可有效控制载荷大小。研究表明飞行器在30°斜浪工况下降落时载荷最小,而逆浪降落时载荷过高。在四级海况下,不论顺浪、逆浪、平行波浪或斜浪降落场景,安装此型号水橇的模型飞机相较于未安装水橇的模型机,其垂向载荷均有不同程度的减少,验证了该水橇设计在波浪环境下仍能有效改善降落载荷性能。最后,针对上述部分得到的参数范围内的最优形式的水橇,利用STAR-CCM+软件进行了数值模拟仿真,研究了飞行器降落时的水平速度,垂直速度,初始仰角对其降落时砰击载荷的影响以及对水橇降载效果的影响:(1)水平速度对飞行器着水载荷的影响较小。随着水平速度由30 m/s增至50 m/s,载荷峰值增长较为平缓;但当水平速度达到60 m/s以上时,着水瞬间的峰值载荷确反而减小,这是由于气动升力大于重力,导致垂直速度下降,从而降低了着水瞬间的峰值载荷,侧面反映出垂直速度对砰击载荷的影响大于水平速度。(2)垂直速度对飞行器在着水瞬间所承受的垂向载荷具有显著影响。当垂直速度从0.5 m/s提升至2 m/s时,飞行器接触水面瞬间所承受的最大载荷出现了急剧增长,增幅达到了初始值的两倍。在这个速度从0.5增加至2 m/s的过程中,不同工况下飞行器受到的垂向载荷峰值增量呈现逐渐减小的趋势,同时这些峰值之间的时间间隔也在不断缩短。(3)随着仰角增加,飞行器机腹中后部入水时卷入空气产生负压增大,导致艏仰力矩增强和艏仰角加速度增大,从而使飞行器尾翼提前接触水面,由于接触速度减小,所以减少了着水时的最大砰击载荷。此外,随着初始仰角增加,飞行器机腹接触水面时的水平投影面积减小,直接降低了首次机腹入水时的砰击载荷。另一方面,在6-10°初始仰角范围内,安装的水橇能有效降低着水载荷,尤其是在10°时效果最佳。然而,当初始仰角超过10°时,水橇不再具备降载效果,这是因为随着仰角继续增大,水橇板接触水面时的迎水面积也随之增大,从而增加了水橇着水时的砰击载荷。更多还原

【Abstract】 Waterborne aircraft,such as seaplanes and ground effect vehicles,due to their amphibious nature,speed,and long-range capabilities,hold significant potential for development in both civilian and military applications.The advancement of these waterborne craft faces several critical issues that need resolution: enhancing payload capacity,improving safety,and increasing stability during wave travel along with resistance against wave impact.As a result,the evolution of ground effect vehicles and amphibious aircraft inevitably heads towards larger scale designs.However,this enlargement introduces substantial challenges in terms of structural stability and safety when they land on water surfaces,necessitating an evaluation of the water impact process and proposing methods to mitigate water impact loads and enhance the aircraft’s landing attitude stability.This study initially employs STAR-CCM+ software for numerical simulation analysis,which is validated through wedge entry experiments and referencing NACA TN 2929 A model water landing experiments.It investigates the damping performance of a dual-plate hydro-ski designed by the NACA laboratory under varying length-to-width ratios,static load factors,and keel angles,which effectively reduces peak vertical loads during water landings.The findings reveal that the dual-plate hydro-ski breaks down a single contact event into two contacts upon water landing,thereby effectively lowering peak impact loads.This effect can be optimized by suitably adjusting hydro-ski parameters.Specifically,the ideal range for the static load factor is between 20 to 60,ensuring minimal shock loads without unduly reducing hydro-ski size or its damping capability.The length-to-width ratio of the hydro-ski should also be maintained within the 1 to 3 range to guarantee adequate contact area and effective damping performance.Additionally,the keel angle should be set at 0° to 4.5° to appropriately adjust the horizontal and vertical projection areas,thus reducing the impact force and pitch moment at water contact,minimizing the vertical load upon initial contact with the aircraft’s belly and stabilizing the aircraft’s attitude during the landing phase.The installation position of the hydro-ski is crucial too;it is recommended to place it 0-0.03 times the aircraft length ahead or behind the center of gravity to ensure effective control over the aircraft’s attitude and reduction of loading during water landings.Subsequently,based on the suggested ranges for hydro-ski parameters derived from the research,an integrated method using experimental design,BP neural network,and multi-island genetic algorithm is employed to optimize the hydro-ski parameters.Upon reverse normalization of the optimal parameter combination,the optimal shape parameters for the hydro-ski and its installation location are obtained.Experimental validation shows that when installed on an aircraft model,the optimized hydro-ski significantly reduces the vertical load during the landing process by approximately 51.6% compared to the original model and a standard hydro-ski,while greatly enhancing the aircraft’s landing attitude stability by around90.9%.Following this,the relative optimal form of the dual-plate hydro-ski obtained from the optimization is further studied using STAR-CCM+ software through numerical simulations.This investigation delves into the variation patterns of loads during the landing process under different wave directions and landing positions,as well as the effects of various working conditions on the optimized hydro-ski’s damping performance.The study reveals that the hydroski converts the aircraft’s water contact process into two separate events,thereby lessening the peak vertical loads,and that adjusting hydro-ski parameters can effectively control the load magnitude.It is demonstrated that the minimum landing loads occur when the aircraft lands under 30° cross-wave conditions,while head-on wave landings generate excessively high loads.Under Sea State 4 conditions,regardless of the landing scenarios involving following waves,opposing waves,parallel waves,or oblique waves,the model aircraft equipped with this type of hydro-ski experienced varying degrees of reduced vertical loads compared to models without the hydro-ski,thereby validating the effectiveness of the hydro-ski design in improving landing load performance even in a wave environment.Finally,using STAR-CCM+ software,numerical simulations were conducted on the optimal form of the hydro-ski within the derived parameter ranges to investigate the effects of horizontal velocity,vertical velocity,and initial pitch angle on the water impact loads during landing and on the hydro-ski’s damping performance:(1)Horizontal velocity has a relatively minor influence on the water impact loads of the aircraft.With the horizontal velocity increasing from 30 m/s to 50 m/s,the load peak grows moderately.However,when the horizontal velocity exceeds 60 m/s,the peak load at touchdown actually decreases.This occurs because the aerodynamic lift surpasses the weight,causing a decrease in vertical velocity,which in turn lowers the peak load at touchdown,indicating that vertical velocity has a greater impact on impact loads than horizontal velocity.(2)Vertical velocity significantly affects the maximum vertical load experienced by the aircraft at the moment of water contact.When the vertical velocity increases from 0.5 m/s to 2 m/s,the maximum load sustained by the aircraft at the instant of water contact escalates sharply,reaching double its initial value.Throughout the increase from 0.5 to 2 m/s,the increments in the peak vertical loads under different conditions show a gradually decreasing trend,while the time intervals between these peaks continuously shorten.(3)As the pitch angle increases,the negative pressure caused by air ingestion beneath the mid-to-aft part of the aircraft’s belly intensifies,leading to an increase in the pitching moment and pitching angular acceleration,causing the tail section of the aircraft to make contact with the water surface earlier.Due to the decreased contact speed,this results in a reduction of the maximum impact load during landing.Moreover,with the increase in the initial pitch angle,the horizontal projection area of the aircraft’s belly at water contact diminishes,directly reducing the first impact load when the belly enters the water.On the other hand,within the range of initial pitch angles from 6 to 10°,the installed hydro-ski effectively reduces water impact loads,with the best performance observed at 10°.Nevertheless,when the initial pitch angle surpasses 10°,the hydro-ski loses its damping effect.This is because as the pitch angle continues to increase,the wetted area of the hydro-ski plates upon contacting the water surface also increases,thereby raising the impact loads during the hydro-ski’s water contact.更多还原