低重力环境是进行空间探索必须面对的一个重要物理条件。在低重力环境下，重力效应减弱甚至消失。此时，重力带来的浮力对流消失，进而变为毛细效应、惯性效应主导的流动。空间推进剂贮箱作为航天器的重要部件之一，其内部流体管理涉及到对贮箱内流动、压力、温度等几个因素耦合作用的控制，对于整个系统的有效运行至关重要。尤其是贮箱内的液体晃动、相变传热引起的自增压以及液体的流动控制等是目前研究的热点问题。因此，本文开展了低重力环境贮箱内流体动力学行为以及相变传热自增压问题的研究。主要包括以下几个方面的内容：

利用北京落塔实验和数值模拟方法开展了微重力环境下部分充液的半胶囊罐型贮箱内液体的动态行为的研究。结合动态接触角模型，研究了贮箱内自由液面的动态演化规律，对比并分析了静态接触角与动态接触角模型对自由液面动态行为的影响，以及贮箱内液体工质的充液量对自由液面振荡的影响规律。结果表明，重力突降后的模型贮箱中内自由液面的弯曲变形表现出阻尼振荡的特性，振荡频率和贮箱特征尺寸（半径）之间存在f ~ R^-3/2的标度关系。

在落塔实验验证了数值模拟方法有效性的基础上，以乙醇为工质，开展了重力突降的全胶囊罐型贮箱内的液体晃动规律研究。分析了不同重力水平和充液量对贮箱内自由液面振荡的影响，揭示了空间低（微）重力贮箱内液体晃动的基本规律。结果表明全胶囊罐贮箱内的液体的晃动满足欠阻尼振荡（低、高充液量）和近临界阻尼振荡（中间充液量）规律，低（≥ 10^-3g₀）、微（< 10^-3g₀）重力条件下贮箱内液体的晃动模式相似，但残余重力的存在对于气枕平衡状态位形以及振荡频率、幅值、持续时间均有较大的影响。

以低重力贮箱内弯液面气液相分布为前提，从重力水平、充液量、热流边界条件三个方面系统开展了胶囊罐型空间贮箱内相变传热传质及其自增压特性的研究。对比揭示了贮箱内两相流动的流场分布规律，分析了贮箱内的热分层和压力分层现象，总结了贮箱内平均温度、平均压力以及传质率随时间的变化规律。揭示了贮箱内相变传热传质及自增压过程的机理和基本规律。结果表明，当贮箱壁面发生漏热时，其内部热分层和压力分层表现为重力方向的梯度分布，平均温度和平均压力随时间以指数的形式增加。低重力条件下贮箱内的弯液面分布对相变传热传质及其自增压有较大影响。

开展了利用非对称交流电渗驱动技术来进行空间贮箱内残余液体主动式控制问题的研究。与空间贮箱内低充液量残余液体在贮箱壁面形成的毫米级厚度液膜相对应，进行了微通道内非对称交流电渗驱动技术的优化研究，获得了优化的非对称交流电渗驱动的物理及几何通道参数。在此基础上开展了顶端自由液面通道的非对称交流电渗驱动性能的研究，以此作为实现空间贮箱毫米级液膜的残余液体主动式控制的基础。

本文的研究涵盖了低重力贮箱内液体的动力学行为、相变传热传质及自增压、残余液体的主动式控制三个方面，初步揭示了该问题的基本机理及物理规律。

The low gravity environment is an important physical condition that must be faced in space exploration. In low gravity environment, the effect of gravity weakens or even disappears. Thus, the buoyancy convection caused by gravity disappears, and then it becomes a flow dominated by capillary effect and inertial effect. The space propellant tank is one of the important parts of the spacecraft. Its internal fluid management involves the control of the coupling effect of several factors such as flow, pressure, and temperature in the tank, which is essential for the effective operation of the entire system. Especially the liquid sloshing, the self-pressurization caused by the phase change heat transfer and the flow control of liquid in a tank are hotspots in recent studies. Therefore, this paper has carried out the research on the fluid dynamics and the self-pressurization of phase change heat transfer in low gravity environment. It mainly includes the following aspects:

Using the Beijing Drop Tower experiment and numerical simulation methods, the dynamic behavior of the liquid in a partially filled semi-capsule tank in a microgravity environment was studied. Combined with the dynamic contact angle model, the dynamic evolution of the liquid free surface in the tank was studied, and the influence of the static contact angle and the dynamic contact angle model on the dynamic behavior of the liquid free surface was compared and analyzed, as well as the influence of the filling level on the oscillation of the liquid free surface. The results show that the deflection of the free surface in the model tank after abrupt drop of gravity exhibits the characteristics of damping oscillation, and there exists a scale relationship of f ~ R^-3/2 between the oscillation frequency and the characteristic size (radius) of the tank.

Based on the Beijing Drop Tower experiment to verify the effectiveness of the numerical simulation method, the study of the liquid sloshing in a capsule tank with gravity drop was carried out using ethanol as the working fluid. The influence of gravity level and filling level on the free surface oscillation in a tank was analyzed, and the basic law of liquid sloshing in low (micro) gravity is revealed. The results show that the liquid sloshing in a capsule tank satisfies the law of underdamped oscillation for low and high filling levels and near critical damped oscillation for intermediate filling level. The sloshing mode of the liquid in a capsule tank under low (≥ 10^-3g₀) and micro (< 10^-3g₀) gravity is similar. Nevertheless, the existence of residual gravity exhibit an obvious impact on the equilibrium configuration of the ullage and the oscillation frequency, amplitude, and duration in a tank.

On the premise of the phase distribution in low gravity, the phase change, heat and mass transfer and the self-pressurization characteristics in a capsule storage tank were systematically studied from three aspects: gravity level, liquid filling level, and heat flux boundary condition. The study reveals the flow field distribution and the phenomenon of thermal and pressure stratification in a storage tank, and summarizes the law of the average temperature, average pressure and mass transfer rate in a storage tank as functions of time. The study also reveals the mechanism and basic laws of phase change, heat and mass transfer and self-pressurization process in the tank. The results show that when heat leakage occurs at the wall of the storage tank, the internal thermal stratification and pressure stratification appear as a gradient distribution in the direction of gravity, and the average temperature and average pressure increase exponentially with time. The distribution of the meniscus in a tank under low gravity condition exhibits great influence on phase change, heat and mass transfer and self-pressurization.

The study carried out the research on the active drive of the residual liquid in a tank in low (micro) gravity using the asymmetric alternating current electroosmotic (ACEO) technology. Corresponding to the millimeter scale of liquid film thickness formed on the inner wall of a storage tank by the the residual liquid with low filling level in space, the optimization study of the asymmetric ACEO technology in a microchannel was carried out, and obtained the optimized physical and geometric parameters. Then the study of the asymmetric ACEO with free surface boundary condition on top of the microchannel was carried out based on the optimized parameters, which shows a promising use for the active control of the residual liquid with millimeter scale of film thickness in a storage tank in low (micro) gravity condition.

The research in this paper covers three aspects: the dynamic behaviors of the liquid, the phase change, heat and mass transfer and self-pressurization, and the active control of the residual liquid in a storage tank in low gravity condition. These studies reveal the basic mechanism and physical laws of the above problem.