Transition to Oscillatory and Chaotic Flows in Marangoni Convection of Liquid Bridge (Towards an On-Orbit Experiment aboard the International Space Station)

针对2005年国际空间站在轨实验，对半区液桥中的Marangoni对流进行了实验和数值研究。在同轴圆柱形杆之间形成半区液体。杆之间的温差引起的热毛细对流的自由表面的桥梁。在临界温差或临界Marangoni数下，热柱驱动流动表现出从二维稳态到三维“振荡”流动的转变。在低温环境中进行了一系列实验，以便抑制流体的蒸发，同时实现桥两端之间的大温差，以获得高的马兰戈尼数，桥的尺寸小（直径为5 mm，高度为几mm）。此外，还应用三维粒子跟踪测速技术（3-D PTV）测量了 关于我们 小尺寸液桥中热毛细流动的三维流场。通过在蓝宝石玻璃制成的透明顶杆上方放置一个小棱镜，可以从顶端表面同时观察两个CCD相机。从一系列实验中，获得了以下结果：（1）计算了液桥直径、纵横比和流体粘度对转捩临界条件和转捩后的模态结构的影响;（2）用三维PTV重建了定常流和振荡流的三维速度场;（3）发现了远远超过临界条件的新型脉动和旋转振荡流;（4）通过由表面温度变化重构伪相空间和计算关联维数，实现并分析了混沌和湍流流。此外，在数值研究中还取得了以下成果：（1）开发了高Pr数流体在高Ma数下的流场计算程序，（2）对高Ma数下的混沌流动和湍流流动进行了非线性分析，这些结果对非线性流体的制备具有重要意义。轨道实验和建立分析国际空间站数据的方法以及了解该系统中的流体动力学。少

Aiming at an on-orbit experiments aboard the International Space Station(ISS) in 2005, experimental and numerical studies on the Marangoni convection in a half-zone liquid bridge have been carried out. A half-zone liquid was formed between the coaxial cylindrical rods. The temperature difference between the rods induced the thermocapillary convection over the free surface of the bridge. The thermocaPillary-driven flow exhibited a transition from the 2D steady to the 3D 'oscillatory' flows at a critical temperature difference or a critical Marangoni number.In the present study, a series of experiments was performed in a low temperature environment in order to suppress the evaporation of fluid while realizing a large temperature difference between the both ends of the bridge to attain a high Marangoni number in spite of a small size of the bridge (5mm in diameter and a few mm in height). In addition the three-dimensional particle tracking velocimetry (3-D PTV) was applied to measure the … More 3-D flow field of the thermocapillary flow in the small-size liquid bridge. The simultaneous observation with two CCD cameras from the top-end surface was enabled by the application of a small prism placed above the transparent top rod made of sapphire glass. From the series of experiments, following results were obtained ; (1)the critical condition of the transition and the modal strucure after the transition were evaluated as a function of the liquid bridge diameter, aspect ratio and the fluid viscosity, (2)the 3-D velocity fields of the steady and oscillatory flows were reconstructed by 3-D PTV, (3)new types of pulsating and rotating oscillatory flows far beyond the critical condition were found and (4)chaotic and turbulent flows were realized and analyzed by the reconstruction of the pseudo-phase space from the surface temperature variation and by the evaluation of the correlation dimension. In addition, following results were achieved in the numerical study ; (1)a numerical code to calculate the flow field of high Pr number fluid at high Ma number was developed, and (2)non-linear analysis of the chaotic and turbulent flows at high Ma number was carried out.These results contributes significantly for preparation of the on-orbit experiment and establishment of the method analyzing data from the ISS as well as for understanding the fluid dynamics in this system. Less