摘要:
软管锥套式空中加油过程涉及气动力、燃油流动、柔性结构变形的复杂耦合,其耦合求解对仿真技术要求高、计算量大,严重制约了软管空中加油的准确性与安全性。为了准确分析软管锥套组合体在对接输油过程中的动力学特性,避开动力学方程建模的劣势,提出了一种考虑气动力、尾涡、软管变形与气流场双向影响、燃油内部流动综合影响下软管锥套组合体结构变形过程的流固耦合有限元模型及求解方法。模型中计算了稳定伞的作用效果并等效解耦成力和转角边界条件,推导了机翼尾涡作用力方程,采用联合仿真技术进行了流固耦合分析。将软管拖曳平衡状态的计算结果与真实试验数据对比,吻合性良好。通过进一步仿真计算,对燃油流动、对接参数及飞行参数等甩鞭现象产生的影响因素进行了分析。结果表明,对接速度和回收加速度的匹配关系是甩鞭载荷的主要影响因素,回收加速度与最优匹配对接速度大小正相关。其次,飞行参数是次要影响因素,在不考虑燃油流动时,每一种高度下都呈现出“飞行速度越高,甩鞭载荷越低”的特点。燃油流动是一项干扰因素,一定程度会干扰上述规律,但不会影响整体规律,需要针对工况进行分析。
Abstract:
The hose-drogue aerial refueling process involves the complex coupling of aerodynamic force, fuel flow, and flexible structure deformation. Solving these interactions required advanced simulation techniques and significant computational resources, which posed challenges to the accuracy and safety of practical implementations. A novel fluid-solid coupling model and methodology integrated aerodynamic loads, wake vortex effects, hose flexibility, airflow, and internal fuel flow were developed to analyze structural deformation of Hose-Drogue Assembly during docking and fuel transfer phases, overcoming limitations of traditional kinetic equation modeling. The aerodynamic forces of the paradrogue were obtained by performing separate CFD modeling on the paradrogue and conducting steady-state calculations. Meanwhile, the stabilizing moment of the paradrogue was equivalently converted into the lateral and rotational boundary condition at the center point of the paradrogue. Subsequently, based on the Hallock-Burnham model, the analytical expressions of the aerodynamic loads on the Hose-Drogue Assembly under the action of the wake vortex alone were derived, and the aerodynamic loads were applied to Hose-Drogue Assembly by abaqus subroutine. With the proposed model, the multi-stage operational processes of hose-drogue aerial refueling including steady-state, docking-state, and refueling-state were calculated. And, fluid-solid coupling simulations, conducted through Co-simulation, demonstrated excellent agreement with experimental data, particularly in terms of steady-state. Furthermore, the influence of fuel flow characteristics, docking parameters, and flight parameters were systematically identified. The results show that the matching relationship between the docking speed and retracting acceleration is the main influencing factor of whiplash load, retracting acceleration is positively correlated with the magnitude of the optimally matched docking velocity. In addition, the flight parameters are the secondary influencing factors, when the fuel flow is not considered, at each altitude it is established that the higher the flight speed, the lower the whiplash load. Fuel flow dynamics act as a disturbing factor that partially perturbs the established relationship between whiplash loads and key operational parameters. However, these disturbances do not fundamentally alter the overall trend, therefore, condition-specific analyses are imperative to account for fuel flow effects in different situation.