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燃料大幅晃动等几何分析仿真及航天器耦合动力学研究

STUDY ON ISOGEOMETRIC ANALYSIS FOR LARGE-AMPLITUDE PROPELLANT SLOSHING AND SPACECRAFT COUPLED DYNAMICS

  • 摘要: 现代航天器肩负许多周期长且复杂的航天任务, 通常需要携带大量的液体燃料. 贮箱中液体燃料大幅晃动会严重影响航天器的姿态稳定性和控制精度, 是现代航天器耦合动力学建模和精确控制研究的重要问题. 本文提出了一种新的液体大幅晃动数值仿真方法, 采用等几何分析方法对贮箱内气体和液体整体进行建模和空间离散, 采用压力修正的分步法对控制方程进行时间离散, 结合水平集方法划分气体和液体区域并且实时追踪液体晃动自由面. 提出了一种质量修正方法以消除水平集函数演化产生的液体质量误差. 基于燃料大幅晃动等几何分析仿真方法, 对携带太阳能帆板的充液航天器进行动力学建模和耦合运动数值仿真. 对于太阳能帆板的振动问题则采用Kirchhoff-Love板理论建模和模态分析法数值求解. 通过将数值仿真结果与解析解对比, 证明了本文给出方法的正确性. 本文还对燃料大幅晃动下的航天器刚−液−柔耦合运动进行了数值仿真, 发现液体晃动对航天器的姿态变化和结构振动的幅值和频率具有不可忽视的影响.

     

    Abstract: With long mission cycles and complicated space missions, modern spacecraft usually need to carry a lot of liquid propellant. Large-amplitude sloshing of liquid propellant in storage tanks will seriously affect the attitude stability and control accuracy of the spacecraft, which is an important problem for the modeling of the spacecraft coupled dynamics system and the accurate control of orbit and attitude. In this paper, a new computational fluid dynamics method for the numerical simulation of large-amplitude liquid sloshing is proposed. The modeling and spatial discretization of the whole gas and liquid mixed fluid system in the tank are carried out by using isogeometric analysis. The pressure-modified fractional step method is used for the time discretization of the governing equations. By decoupling the pressure and velocity variables, the implicit equations are transformed into the explicit equations to improve the computational efficiency. For the common liquid sloshing problem, a simple and efficient mass correction method is proposed to eliminate the liquid mass error caused by the evolution of level set function. Based on the numerical method of isogeometric analysis for liquid sloshing, the coupled dynamics system of liquid-filled spacecraft with solar panels is modeled and the motion of the coupled spacecraft is simulated. The liquid sloshing momentum equation is transformed and introduced into the spacecraft dynamics equations. The numerically stable rigid-liquid coupled dynamics equations of spacecraft affected by liquid sloshing are established. The modeling of solar panels is based on the Kirchhoff-Love plate theory and the vibration of solar panels is solved by modal analysis. By comparing the numerical simulation results with the analytical results, the correctness of the proposed method is proved. Besides, the motion of rigid-liquid-flexible coupled spacecraft is simulated. It is found that liquid sloshing has a significant effect on the amplitude and frequency of spacecraft attitude change and structural vibration.

     

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