充液陀螺在粗糙平面上的自旋稳定性

本文提出一种确定线性系统运动稳定性的几何方法。利用这个方法研究了充液陀螺在非光滑水平约束面上的自旋稳定性问题,给出了充液系统的自旋运动稳定性在三维参数空间中的几何分布,并对结果进行了讨论。     

一类轴对称充液陀螺系统自旋运动稳定性研究

研究了一类复杂充液旋转对称陀螺（其圆柱形容腔充有互不相溶的双元液体，且带充液圆柱中心杆）的章动振荡与其所充双元液体自由振荡之耦合问题．利用留数方法研究了系统的自旋稳态运动的稳定性条件     

自由液面晃动对旋转充液腔体运动稳定性的影响

针对旋转充液腔体的运动稳定性问题,本文考虑自旋速率范围较宽的情况。引入表示离心力与液体表面张力之比的常数C_f,以Stewartson—Wedemeyer理论和Murphy方法为基础,研究腔内液体晃动对共振不稳定频带的影响。结果表明只有当自旋速率较小,液体表面张力较大时,自由液面晃动对腔体运动稳定性才有明显影响;反之则可忽略自由液面晃动对腔体运动稳定性的影响。     

微重力环境下慢自旋充液容器内的液体晃动

本文研究在表面张力作用下自旋刚性容器内的部分充液液体的自由晃动问题。采用Pfeiffer方法建立了液体自由晃动特征值边值问题,利用边界元法数值求解晃动的特征频率和模态,分别计算给出球腔内的液体晃动关于充液比、微重Bond数和自旋Bond数的特征叛率曲线。     

充液或部分充液转子的动力稳定性

本文讨论了具有内外阻尼的高速充液转子的动力稳定性。首先通过对旋转流体的平面流场的求解，导出充液转子作简谐运动时流体对转子的动压力，由此导出转子的运动方程；讨论了充液转子的动力稳定性，给出了稳定性解析判据和稳定性边界。结果表明，存在转速门槛值，低于该转速时，充液转子可存在稳定区；当高于该转速时，系统永远失稳，这一结论复盖了已有文献的结果。     

充液腔体内复杂流动及其系统动力学研究

分别对旋转和非旋转充液腔体,阐述了腔内液体各种流动求解理论与实验研究的进展, 简述了主要数值模拟方法的应用状况,并从系统动力学角度,讨论了充液腔体耦合系统动力 学中的相关问题.     

燃料消耗下充液航天器等效动力学建模与分析

在轨航天器贮腔内的液体可能表现出多种不同的运动模式, 主要包括液体相对于贮腔的整体性刚体运动、自由液面横向晃动、液体起旋后逐步发生明显的旋转晃动及液体自旋运动; 复合三自由度刚体摆晃动模型能够较为全面地描述这些液体运动模式, 同时为研究起旋阶段的液体晃动动力学问题提供了有效手段. 本文对非线性液体晃动刚体摆复合模型作进一步发展, 考虑模型等效参数随贮腔充液比的变化, 提出了变参数的刚体摆复合模型, 该模型适用于研究燃料消耗下非线性晃动类充液航天器大范围运动耦合动力学问题. 采用刚体摆复合模型对球形贮腔内的液体晃动进行等效后, 基于混合坐标意义下的拉格朗日方程推导了一类充液航天器轨道-姿态-晃动全耦合的动力学方程组, 并展开了充液航天器大角度三轴稳定姿态机动和零冲量轨道机动仿真以及航天器耦合动力学响应特性分析. 研究表明: 液体相对于贮腔的运动会造成航天器主刚体位置发生偏移, 当航天器在执行零冲量机动时, 燃料消耗会造成航天器的轨道平动速度无法收敛到零; 贮腔偏心布放时, 航天器在执行轨道机动过程中贮腔内液体易发生剧烈而且形式复杂的晃动行为, 进而可能造成航天器刚体运动的不稳定.      

EQUIVALENT DYNAMICS MODELING AND ANALYSIS OF LIQUID-FILLED SPACECRAFT WITH FUEL CONSUMPTION 1)

在轨航天器贮腔内的液体可能表现出多种不同的运动模式, 主要包括液体相对于贮腔的整体性刚体运动、自由液面横向晃动、液体起旋后逐步发生明显的旋转晃动及液体自旋运动; 复合三自由度刚体摆晃动模型能够较为全面地描述这些液体运动模式, 同时为研究起旋阶段的液体晃动动力学问题提供了有效手段. 本文对非线性液体晃动刚体摆复合模型作进一步发展, 考虑模型等效参数随贮腔充液比的变化, 提出了变参数的刚体摆复合模型, 该模型适用于研究燃料消耗下非线性晃动类充液航天器大范围运动耦合动力学问题. 采用刚体摆复合模型对球形贮腔内的液体晃动进行等效后, 基于混合坐标意义下的拉格朗日方程推导了一类充液航天器轨道-姿态-晃动全耦合的动力学方程组, 并展开了充液航天器大角度三轴稳定姿态机动和零冲量轨道机动仿真以及航天器耦合动力学响应特性分析. 研究表明: 液体相对于贮腔的运动会造成航天器主刚体位置发生偏移, 当航天器在执行零冲量机动时, 燃料消耗会造成航天器的轨道平动速度无法收敛到零; 贮腔偏心布放时, 航天器在执行轨道机动过程中贮腔内液体易发生剧烈而且形式复杂的晃动行为, 进而可能造成航天器刚体运动的不稳定.     

充液系统动力学与航天高技术问题

充液航天器内部液体晃动及其对控制系统的影响,是当前国内外航天高技术研究的重要课题,也是一个比较复杂的问题。本文首先由力学变分原理导出了充液系统的状态方程,其次分析了充液系统的稳定性;特别是,研究了在失重或微重条件下,充液航天器内部液体晃动的动力学特性以及部分充液三轴稳定性问题等。本文的研究结果,对于航天、航空、航海中的充液系统动力学与控制问题,都有重要的参考价值。      

章动角对旋转章动充液腔体运动稳定性的影响

旋转章动充液腔体的运动稳定性，主要分两大类。当Ｒｅｙｎｏｌｄｓ数很小时，出现转速衰减不稳定性，Ｒｅｙｎｏｌｄｓ数增大到一定程度，又出现共振不稳定性。本文考虑Ｒｅｙｎｏｌｄｓ数较大时的情况，此时腔内液体的惯性波振动与腔体的章动频率耦合即可发生共振不稳定性。当章动角增大时，共振频带又发生转移。采用变形参数法讨论章动角增大时弱非线影响，很简明地得出特征值修正公式，并计算了液体力矩的变化曲线。     

Effects of residual stress and viscous and hysteretic dampings on the stability of a spinning micro-shaft

This study examines the effects of the residual stress and viscous and hysteretic dampings on the vibrational behavior and stability of a spinning Timoshenko micro-shaft.A modified couple stress theory(MCST) is used to elucidate the sizedependency of the micro-shaft spinning stability,and the equations of motion are derived by employing Hamilton's principle and a spatial beam for spinning micro-shafts.Moreover,a differential quadrature method(DQM) is presented,along with the exact solution for the forward and backward(FW-BW) complex frequencies and normal modes.The effects of the material length scale parameter(MLSP),the spinning speed,the viscous damping coefficient,the hysteretic damping,and the residual stress on the stability of the spinning micro-shafts are investigated.The results indicate that the MLSP,the internal dampings(viscous and hysteretic),and the residual stress have significant effects on the complex frequency and stability of the spinning micro-shafts.Therefore,it is crucial to take these factors into account while these systems are designed and analyzed.The results show that an increase in the MLSP leads to stiffening of the spinning micro-shaft,increases the FW-BW dimensionless complex frequencies of the system,and enhances the stability of the system.Additionally,a rise in the tensile residual stresses causes an increase in the FW-BW dimensionless complex frequencies and stability of the micro-shafts,while the opposite is true for the compressive residual stresses.The results of this research can be employed for designing spinning structures and controlling their vibrations,thus forestalling resonance.     

Stability and Self‐Oscillations of a Rotor Containing a Conducting Liquid in a Magnetic Field

This paper considers the problem of the stability in the small of the steadystate spinning of a rotor with a cylindrical cavity partly filled with a viscous, incompressible, conducting liquid in a magnetic field. The responses of the buttend boundary layers and the resultant force exerted by the liquid on the rotor performing circular precession of small radius are determined. The plane of the viscoelastic restraint parameters of the rotor axis was Dpartitioned into regions with different degrees of instability is constructed. Steadystate spinning near the boundary of the region of stability in the space of parameters is studied assuming nonlinear responses of the supports. It is shown that passage through the boundary of the region of stability leads to bifurcation of the steadystate spinning regime, resulting in periodic motion of the type of circular precession. The origin ofperiodic motion from steadystate spinning can be subcritical or supercritical.     

Stability of an internally damped non-ideal flexible spinning shaft

The stability domain of an internally damped flexible spinning shaft, which is driven by a non-ideal source, is studied in this paper. It is found that the higher transverse modes may become unstable before the lower ones under certain conditions. In particular, we find the entrainment of the shaft spinning speed at specific values corresponding to the lowest stability threshold among all transverse modes. Moreover, the steady state amplitude of the transverse vibrations when the shaft spinning speed is stuck at the stability threshold is determined analytically. The analytical results thus obtained are validated with numerical simulations.     

自旋液体晃动Pfeiffer方法的分析

本文对研究自旋液体晃动的Pfeiffer方法提出了一种分析方法,从而将液体自由振动的稳定性的Pfeiffer方法推广于既有重力又有自旋的液体晃动的研究。     

CRITICAL LOAD OF AN AXIALLY MOVING LIQUID FIBER IN CRIMPING STUFFER BOX

研究了轴向运动的丝束在填塞卷曲机构内的不稳定性，并得到了临界载荷，同时研究了纺丝参数对丝束弯曲失稳的影响。该理论可用于填塞箱的优化设计或改善产品质量。     

Thermal instabilities in melt spinning of viscoelastic fibers

Nonisothermal melt spinning of viscoelastic fibers for which the viscosity varies in a step-like manner with respect to temperature is studied in this work. A set of one-dimensional equations based on the slender-jet approximation and the upper convected Maxwell model is used to describe the melt spinning process. The process is characterized by the force required to pull the fiber, the strength of external heating, and the draw ratio, the square of the ratio of the fiber diameter at the spinneret to that at the take-up roller. For low levels of elasticity and sufficiently strong external heating, there can be three pulling forces consistent with the same draw ratio, similar to the Newtonian case studied by Wylie et al. [31]. For higher levels of elasticity, the process exhibits a draw ratio plateau where the draw ratio hardly changes with the pulling force, reflecting a competition between thermal and elastic effects. As in the Newtonian case, external heating introduces a new instability – termed thermal instability – that is absent in isothermal systems. Linear stability analysis reveals that external heating improves stability for low levels of elasticity, but can worsen stability for higher levels of elasticity, which is again a consequence of the interplay between thermal and elastic effects. Nonlinear simulations indicate that the predictions of linear stability analysis carry over to the nonlinear regime, and show that unstable systems exhibit limit-cycle behavior. The results of the present work demonstrate a possible mechanism through which external heating can stabilize the melt spinning of viscoelastic fibers.     

自旋液体晃动研究

对旋转对称中心贮箱内的自旋液体晃动问题，提出了一个直接对Ｅｕｌｅｒ方程进行Ｇａｌｅｒｋｉｎ离散的近似方法，并分析了方法的近似性。